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rh1750 rh1750 radiation-hardened implementation mil-std-1750a processor produced gec-plessey marconi communications primary target market aerospace industry
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Computer architecture
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jon callas jon callas american computer security expert software engineer user experience designer technologist co-founder former cto global encrypted communications service silent circle held major positions digital equipment corporation apple pgp entrust considered one respected well-known names mobile security industry callas credited creating several internet engineering task force ietf standards including openpgp dkim zrtp wrote prior work entrust chief technical officer co-founder pgp corporation former chief technical officer entrust website callas describes entrepreneur innovator information business security including cryptography operating system security public key infrastructure intellectual property rights well innovator human-computer interactions collaboration social virtual reality also worked bruce schneier counterpane internet security one primary authors dkim method chief scientist original pgp inc. founded phil zimmermann callas member infosec think tank shmoo group callas received bsc mathematics university maryland college park attended 1977 1980 minored philosophy english literature member technical staff century computing 1980 1981 served principal software engineer digital equipment 1981 1993 working got work wide variety things graphics schedulers memory management operating system security created random password generator digital equipment designed pathworks network operating system well software macintosh client systems server systems running vms unix created cross-platform communications computers running mac os vms unix windows os/2 using appletalk decnet tcp/ip networks also developed software 3d pex ddx openvms osf/1 windows nt digital equipment folded callas co-founded world benders inc. worked 1993 1995 world benders lead architect developer meeting space cross-platform group collaboration product allowed people conduct meetings real-time existing networks callas held title senior scientist ii apple computer 1995 1997 describes firm ’ security privateer designed built next-generation cryptographic security products mac os x ios including 'filevault 2 full-disk encryption product also designed concurrent programming system high-performance computing 'transforms addition led engineering approvals fips 140 validation ios callas trusted security apple operating system worked apple whole disk encryption worst time working apple year steve jobs came back callas said apple worked gursharan sidhu inventor appletalk callas shipped first crypto built os called powertalk said failed far early although colleague bruce gaya managed hack piece password manager called keychain could run without rest powertalk thus rescued oblivion present keychain apple products completely utterly rewritten ’ proud saving joined pgp inc. developer pretty good privacy january 1997 chief scientist network associates nai bought pgp december 1997 callas became cto total network security division nai creating architecture direction company network security products serving primary author ietf openpgp standard director software engineering counterpane 1999 2001 serving co-architect counterpane managed security monitoring system – redundant system adaptive fail-over monitors networks three continents also led engineering team built system taking prototype operational four months managed counterpane export control process getting approval system including fifteen new ciphers senior architect wave systems corporation 2001 2002 lead architect wave embassy trust system performed security analysis created product security subsystems co-founded new pgp corporation 2002 worked server architect pgp july 2002 october 2009 time company principal author ietf openpgp standard rfc2440 developed pgp pretty good privacy universal server security privateer could tell 'd kill associates october 2009 july 2011 chief technical officer entrust provider identity-based security software july 2011 january 2013 co-founded silent circle 2012 blackphone 2013 continued serve cto silent circle april 2016 led development operations groups former produces apps manifest silent circle services subscribers latter runs actual services callas holds patents patents pending several systems methods erasing media facilitating secure media access secure transparent electronic communications dynamic security operations partial message authentication facilitating encryption decryption operations email server callas security product designs major innovation awards wall street journal others one primary authors dkim method member infosec think tank shmoo group served adjunct professor indiana university since 2012 callas lectured widely computers internet security scheduled speaker oslo freedom forum 2014 callas selected one two keynote speakers 2015 pdf technical conference san jose california may 2016 callas rejoined apple callas appeared january 11 2018 episode john wants answers callas stated tech companies bigger threat privacy government views stem big tech mass pooling personal data advertising polarization within silicon valley companies committed privacy many earn revenues selling user data callas stated advertising market takes downturn companies protect users data insulated harm lives san jose california
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Computer security
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vm/386 vm/386 multitasking operating system 'control program took early advantage capabilities intel 386 processor utilizing virtual 8086 mode users able run existing text-based graphical dos software safely separate environments system offered high degree control ability set memory cpu usage limits unique config.sys autoexec.bat files could configured application even different dos versions 1991 vendor announced intentions support dpmi 1.0 vm/386 vm/386 initially developed softguard systems producer copy-protection software plans include features like non-dos system support financial constraints forced sale intelligent graphics corporation igc launched product 1987 pc magazine award technical excellence 1988 company also introduced multi-user version allowed number serial terminals even graphical systems connected single 386 computer current versions software built multi-user support handle tens users networked environment windows 3.11 support access controls virtual memory device sharing among features version software designed cooperate unix bundled everex systems workstations system sees use mainly vertical applications like point-of-sale systems ability run reliably cheap reliable hardware outweigh gains newer operating systems complex less reliable early competition included desqview 386 sunny hill software omniview starpath systems vmos/3 windows/386 2.01 target market shifted away single-user systems multiple-user setups many serial terminals began compete directly likes multiuser dos pc-mos/386
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Operating systems
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professional video ip professional video ip systems use existing standard video codec reduce program material bitstream e.g. mpeg transport stream use internet protocol ip network carry bitstream encapsulated stream ip packets typically accomplished using variant rtp protocol carrying professional video ip networks special challenges compared non-time-critical ip traffic many problems similar encountered voice ip much higher level engineering requirements particular strict quality service requirements must fulfilled use professional broadcast environments since even well-engineered ip networks tend small residual packet loss rate caused low-probability statistical congestion events amplification bit errors underlying hardware professional solutions use kind forward error correction ensure encoded video stream reconstructed even packets lost typically applied packet level since encapsulated video bitstream typically designed tolerate low levels bit burst errors rather loss whole packets resending packets option sequential nature underlying video signal live video resent packet would arrive well arrival next frame video network delay variation kept minimum using high-speed network backbone ensuring video traffic encounter excessive queue delays typically done either ensuring network close full capacity video traffic prioritized using traffic engineering techniques see remaining delay variation removed buffering expense added time delay forward error correction used small proportion packets arriving deadline tolerated since dealt discarded receipt treated way lost packets added time delay particularly unwelcome ptz cameras makes operator control difficult values 250ms problem presented latency variation makes synchronization complex making recovery underlying timing video signal far difficult typically solved genlocking ends system external station sync signals typically generated sources gps atomic clocks thus requiring extraction coarse timing information receiving end order achieve high-quality video synchronization extraction coarse timing data typically done using phase locked loop long time constant even packet loss mitigation video ip work network capable carrying content reasonable maximum packet loss rate practice means video ip work overloaded networks since ip offer traffic guarantees must applied network engineering level one approach quality service approach simply allocates sufficient bandwidth video-carrying traffic congest possible load pattern approaches include dynamic reduction frame rate resolution network admission control bandwidth reservation traffic shaping traffic prioritization techniques require complex network engineering work simple approach building non-blocking network possible see rsvp one approach ip network traffic engineering pro-mpeg wide area network group done much recent work creating draft standard interoperable professional video ip within security products industry ip-based closed circuit television cctv making gains analog market key components ip-based cctv remain consistent analog technologies image capture combination ip-based cameras analog cameras using ip-based encoders image transmission storage retrieval uses technologies raid arrays iscsi recorded indexed video video management affords web browser-enabled management control ip-based cctv systems one key advantage ip-based cctv ability use network infrastructure providing adequate bandwidth availability switching routing rather coaxial cabling however running bandwidth-intensive surveillance video corporate data networks point organizational contention depending potential impact network performance class companies produce video management software help manage capture storage video content digital video also makes possible video content analysis allows automatic detection identification various kinds objects motion also another emerging model off-site storage surveillance video online surveillance providers utilizing cloud computing technologies consolidate multi-site surveillance video web manufacturers cctv equipment steadily integrating ip network technology product portfolios
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Internet protocols
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correlation attack cryptography correlation attacks class known plaintext attacks breaking stream ciphers whose keystream generated combining output several linear feedback shift registers called lfsrs rest article using boolean function correlation attacks exploit statistical weakness arises poor choice boolean function – possible select function avoids correlation attacks type cipher inherently insecure simply essential consider susceptibility correlation attacks designing stream ciphers type correlation attacks possible significant correlation output state one individual lfsr keystream generator output boolean function combines output state lfsrs combined partial knowledge keystream easily derived partial knowledge plaintext two simply xored together allows attacker brute-force key individual lfsr rest system separately instance keystream generator four 8-bit lfsrs combined produce keystream one registers correlated boolean function output may brute force first remaining three total attack complexity 2 2 compared cost launching brute force attack entire system complexity 2 represents attack effort saving factor 256 substantial second register correlated function may repeat process drop attack complexity 2 2 2 effort saving factor 65028 sense correlation attacks considered divide conquer algorithms correlation attacks perhaps best explained via example consider case geffe keystream generator geffe generator consists three lfsrs lfsr-1 lfsr-2 lfsr-3 denote outputs registers formula_1 formula_2 formula_3 respectively boolean function combines three registers provide generator output given formula_4 i.e formula_1 formula_2 xor formula_1 formula_3 2 8 possible values outputs three registers value combining function shown table consider output third register formula_3 table makes clear 8 possible outputs formula_3 6 equal corresponding value generator output formula_11 i.e formula_12 75 possible cases thus say lfsr-3 correlated generator weakness may exploit follows suppose intercept ciphertext formula_13 plaintext formula_14 encrypted stream cipher using geffe generator keystream generator i.e formula_15 formula_16 formula_17 output lfsr-1 time formula_18 etc suppose know part plaintext e.g know formula_19 first 32 bits plaintext corresponding 4 ascii characters text improbable may seem know plaintext valid xml file instance know first 4 ascii characters must xml similar many file formats network protocols standard headers footers guessed easily given intercepted formula_20 known/guessed formula_19 may easily find formula_22 formula_23 xoring two together know 32 consecutive bits generator output may begin brute force search space possible keys initial values lfsr-3 assuming know tapped bits lfsr-3 assumption line kerckhoffs principle given key keyspace may quickly generate first 32 bits lfsr-3 output compare recovered 32 bits entire generator output established earlier 75 correlation output lfsr-3 generator know correctly guessed key lfsr-3 approximately 24 first 32 bits lfsr-3 output match corresponding bits generator output guessed incorrectly expect roughly half 16 first 32 bits two sequences match thus may recover key lfsr-3 independently keys lfsr-1 lfsr-2 stage reduced problem brute forcing system 3 lfsrs problem brute forcing single lfsr system 2 lfsrs amount effort saved depends length lfsrs realistic values substantial saving make brute force attacks practical need stop observe table formula_2 also agrees generator output 6 times 8 correlation 75 correlation formula_2 generator output may begin brute force attack lfsr-2 independently keys lfsr-1 lfsr-3 leaving lfsr-1 unbroken thus able break geffe generator much effort required brute force 3 entirely independent lfsrs meaning geffe generator weak generator never used generate stream cipher keystreams note table formula_1 agrees generator output 4 times 8 50 correlation use brute force lfsr-1 independently others correct key yield output agrees generator output 50 time average incorrect key represents ideal situation security perspective combining function formula_11 chosen correlation variable combining function output close possible 50 practice may difficult find function achieves without sacrificing design criteria e.g period length compromise may necessary example illustrates well relatively simple concepts behind correlation attacks perhaps simplifies explanation precisely brute forcing individual lfsrs proceeds make statement incorrectly guessed keys generate lfsr output agrees generator output roughly 50 time given two random bit sequences given length probability agreement sequences particular bit 0.5 however specific individual incorrect keys may well generate lfsr output agrees generator output less often exactly 50 time particularly salient case lfsrs whose correlation generator especially strong small enough correlations certainly outside realm possibility incorrectly guessed key also lead lfsr output agrees desired number bits generator output thus may able find key lfsr uniquely certainty may instead find number possible keys although still significant breach cipher security say megabyte known plaintext situation would substantially different incorrect key may generate lfsr output agrees 512 kilobytes generator output likely generate output agrees much 768 kilobytes generator output like correctly guessed key would rule weaker correlation individual register generator output known plaintext required find register key high degree confidence readers background probability theory able see easily formalise argument obtain estimates length known plaintext required given correlation using binomial distribution correlations exploited example attack geffe generator examples called first order correlations correlations value generator output individual lfsr possible define higher order correlations addition instance may possible given boolean function strong correlations individual registers combines significant correlation may exist boolean function two registers e.g formula_28 would example second order correlation define third order correlations obvious way higher order correlation attacks powerful single order correlation attacks however effect subject law limiting returns table shows measure computational cost various attacks keystream generator consisting eight 8-bit lfsrs combined single boolean function understanding calculation cost relatively straightforward leftmost term sum represents size keyspace correlated generators rightmost term represents size keyspace remaining generators higher order correlations lead powerful attacks also difficult find space available boolean functions correlate generator output increases number arguments function boolean function formula_29 n variables said -th order correlation immune -th order correlation immunity integer significant correlation exists function output boolean function inputs example boolean function first order second order correlations third order correlation exhibits 2nd order correlation immunity obviously higher correlation immunity makes function suitable use keystream generator although thing needs considered siegenthaler showed correlation immunity boolean function algebraic degree n variables satisfies ≤ n given set input variables means high algebraic degree restrict maximum possible correlation immunity furthermore function balanced ≤ n − 1 follows impossible function n variables n -th order correlation immune also follows fact function written using reed-muller basis combination xors input functions given possibly extreme severity correlation attack impact stream cipher security considered essential test candidate boolean combination function correlation immunity deciding use stream cipher however important note high correlation immunity necessary sufficient condition boolean function appropriate use keystream generator issues consider e.g whether function balanced whether outputs many roughly many 1 0 possible inputs considered research conducted methods easily generating boolean functions given size guaranteed least particular order correlation immunity research uncovered links correlation immune boolean functions error correcting codes
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Computer security
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penny black research project penny black project microsoft research project tries find effective practical ways fighting spam identifying spams consumes recipient time idea make sender emails pay certain amount sending currency mode payment could cpu cycles turing tests memory cycles payment would limit spammers ability send large quantities emails quickly project name derived penny black world first adhesive stamp used paid postage goal project move e-mail costs receiver sender general idea sender must prove expended certain amount effort specifically receiver message alone project aims devise method without introducing additional challenge-response mechanisms third parties without requiring extra maintenance updates retaining current architecture e-mail system one project ideas ticket server credit-based method validating emails tickets would required perform actions sending emails three operations ticket server provides request ticket cancel ticket refund ticket server would allow user request ticket exchange proof work expending cpu cycles solving hard algorithms processing power turing tests even paying money server could also cancel ticket example receiving email ticket receiver could request ticket cancelled reused person cancels ticket also option refund ticket sender causes original sender regain new ticket example user might refund ticket came email spam using friendly trusted emails would little cost tickets would frequently refunded however spammers would required invest either lot computing time money order create enough tickets send large numbers e-mails one obvious flaws project entirely stop spam hopes slow spam enough longer cost effective spammers using methods reduce spam also require policies universal amongst mail clients intended mass email may also work intended example subscribers particular email service may end getting emails significant delay email service also become increased expenses provider
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Computer security
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dixie dixie obsolete protocol accessing x.500 directory services dixie intended provide lightweight means clients access x.500 directory services dixie allowed tcp/ip clients connect dixie-to-dap gateway would provide access x.500 directory service design allows client access directory without requiring support cumbersome open systems interconnection protocol stack dixie created 1990 university michigan tim howes mark smith bryan beecher dixie formally specified rfc 1249 published 1991 university offered completed unix implementation protocol including dixie server application development library dixie clients dixie client apple macintosh also provided efforts led development lightweight directory access protocol ldap replaced dixie created acronym dixie stand anything however later became known stand directory interface x.500 implemented efficiently
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Internet protocols
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warrant canary warrant canary method communications service provider aims inform users provider served secret government subpoena despite legal prohibitions revealing existence subpoena warrant canary typically informs users secret subpoena particular date canary updated time period specified host warning removed users assume host served subpoena intention allow provider warn users existence subpoena passively without disclosing others government sought obtained access information records secret subpoena secret subpoenas covered 18 u.s.c §2709 c usa patriot act provide criminal penalties disclosing existence warrant third party including service provider users united states secret subpoenas national security letters originated 1986 electronic communications privacy act used suspected agents foreign power revised 2001 patriot act secret subpoenas used anyone may information deemed relevant counter-intelligence terrorism investigations idea using negative pronouncements thwart nondisclosure requirements court orders served secret warrants first proposed steven schear cypherpunks mailing list mainly uncover targeted individuals isps also suggested used public libraries 2002 response usa patriot act would force librarians disclose circulation history patrons first commercial use warrant canary us cloud storage provider rsync.net began publishing canary 2006 addition digital signature provides recent news headline proof warrant canary recently posted well mirroring posting internationally november 5 2013 apple became prominent company publicly state never received order user data section 215 patriot act september 18 2014 gigaom reported warrant canary statement appear anymore next two apple transparency reports covering july–december 2013 january–june 2014 tumblr also included warrant canary transparency report issued february 3 2014 august 2014 online cloud service spider oak implemented encrypted warrant canary publishes clear message every 6 months three pgp signatures geographically distributed signers must sign message — government agency forced spideroak update page would need enlist help three signers september 2014 us security researcher moxie marlinspike wrote every lawyer 've spoken indicated 'canary remove choose update would likely legal consequences simply posting something explicitly says 've received something matter court exercising judicial power warrant could obtained another person prohibits disclosure existence non-existence however could easily remedied amalgamating right fair trial warrant canary australia everyone right fair trial case law larger picture law right access lawyer one write warrant canary way seeks access legal representation may effect triggering canary informing larger public existence secret warrant authority object remove notice seeking legal representation could seen authority infringement legal right australia goal canary effectively causing stay proceedings common law jurisdictions would cure inherent prohibition reducing warrant canaries matter negative positive action addition notice removal notice whatever case may australia outlawed use certain kind warrant canary march 2015 making illegal journalist disclose information existence non-existence warrant issued new mandatory data retention laws unlikely journalist could give correct canary situation anyway legislation agency obtaining warrant compelled inform journalist warrant afterwards computer security privacy specialist bruce schneier wrote blog post p ersonally never believed warrant canaries would work relies fact prohibition speaking n't prevent someone speaking courts generally n't impressed sort thing easily imagine secret warrant includes prohibition triggering warrant canary know right secret legal proceedings issue said case law specific united states would render covert continuance warrant canaries subject constitutionality challenges west virginia state board education v. barnette wooley v. maynard rule free speech clause prohibits compelling someone speak one wishes easily extended prevent someone compelled lie new york times co. v. united states protects one exercising first amendment publish government information even wishes government except grave exceptional circumstances previously set act precedent latter also carries weight acting direct government intervention similar government intervention warrant canary following list companies organizations whose warrant canaries longer appear transparency reports 2015 coalition organizations consisting eff freedom press foundation nyu law calyx institute berkman center created website called canary watch order provide compiled list companies providing warrant canaries mission provide prompt updates changes canary state often difficult users ascertain canary validity thus canary watch aimed provide simple display active canaries blocks time active may 2016 announced canary watch longer accept submissions new canaries monitor existing canaries changes take downs coalition organizations created canary watch explained decision discontinue project stating achieved goals raise awareness illegal unconstitutional national security process including national security letters secret court processes electronic frontier foundation also noted fact canaries non-standard makes difficult automatically monitor changes takedowns
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Computer security
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comparison opengl direct3d direct3d opengl competing application programming interfaces apis used applications render 2d 3d computer graphics hardware acceleration process commonplace since approximately 1999. graphics processing units gpus almost always implement one version apis examples include directx 9 opengl 2 circa 2004 directx 10 opengl 3 circa 2008 recently directx 11 opengl 4 circa 2011 gpus support recent versions standards backward-compatible applications use older standards example one run older directx 9 games recent directx 11-certified gpu direct3d application development targets microsoft windows platform opengl api open standard means various hardware makers operating system developers freely create opengl implementation part system opengl implementations exist wide variety platforms notably opengl dominating graphics api unix-like computer systems application developer perspective direct3d opengl equally open full documentation necessary development tools available restrictions detail two computer graphics apis following note many essential opengl extensions methods although documented also patented thus imposing serious legal troubles implement see issues mesa opengl direct3d implemented display device driver significant difference however direct3d implements api common runtime supplied microsoft turn talks low-level device driver interface ddi opengl every vendor implements full api driver means api functions may slightly different behavior one vendor next glsl shader compilers different vendors also show slightly different behavior following compares two apis structured around various considerations mostly relevant game development proprietary direct3d officially implemented microsoft windows family operating systems including embedded versions used xbox family video game consoles sega dreamcast several mostly functional reimplementations direct3d api made third parties wine project port common windows apis unix-like operating systems cedega proprietary fork wine however process progressively impeded due interdependence directx upon many proprietary components windows direct3d proprietary nature requires difficult process reverse engineering opengl implementations available across many platforms including microsoft windows unix-based systems mac os x linux nintendo sony developed libraries similar identical opengl subset opengl chosen main graphics library android blackberry ios symbian opengl es form microsoft opengl driver provides hardware acceleration windows vista support dropped windows xp soon failed deliver fahrenheit graphics api low level support opengl-direct3d merger late 1990s opengl hardware acceleration windows achieved users first installing installable client drivers icds developed gpu makers icds virtually cases bundled standard driver download package hardware vendor ihv installing recent graphics drivers sufficient provide hardware opengl support recently google almost native graphics layer engine angle project provides means convert opengl es 2.0 application calls directx 9 done webgl subset variant opengl web run common direct3d runtime means less variation vendors first version direct3d 1996 elicited broad criticism even simple operations state changes required creating submitting objects called execute buffers contrast opengl state changes performed one function call direct3d model frustrated many programmers famous complaint made high-profile game developer john d. carmack codice_1 file urged microsoft abandon direct3d favor opengl chris hecker made similar request open letter microsoft april–may 1997 issue game developer magazine version 5 second version named reflect release part directx 5 replaced execute buffers new drawprimitive api still considered cumbersome chris hecker open letter microsoft referred drawprimitive immature poorly-designed clone opengl missing architectural decisions make opengl fast despite controversy microsoft continued evolve api detailed history releases added features given microsoft direct3d web pages former critics direct3d acknowledge direct3d good better opengl abilities ease use january 2007 john carmack said …dx9 really quite good api level even direct3d side things know long history people thinking 'm antagonistic microsoft done good job sensibly evolving step—they 're worried breaking backwards compatibility—and pretty clean api especially like work 'm 360 probably best graphics api far sensibly designed thing 've worked design features direct3d remained unchanged since version one notably reliance microsoft component object model com one advantage using com api used com-aware language notably object pascal delphi microsoft visual c++ c visual basic .net opengl specification implemented programming language c though used languages built concept state machine api opengl depends one programming language feature made callable almost language proper bindings bindings exist current programming languages general direct3d designed virtualize 3d hardware interfaces direct3d frees game programmer accommodating graphics hardware opengl hand designed 3d hardware-accelerated rendering system may emulated software two apis fundamentally designed two separate modes thought functional differences two apis work one functional difference apis manage hardware resources direct3d expects application opengl makes implementation tradeoff opengl decreases difficulty developing api time increasing complexity creating implementation driver performs well direct3d developer must manage hardware resources independently however implementation simpler developers flexibility allocate resources efficient way possible application 2005 another functional difference apis way handled rendering textures direct3d method codice_2 convenient prior versions opengl required manipulating pixel buffers p-buffers cumbersome risky codepath used program different anticipated driver maker code would fall back software rendering causing substantial performance drop however broad support frame buffer objects extension provided opengl equivalent direct3d method successfully addressed shortcoming render target feature opengl brought par direct3d aspect outside minor functional differences mostly addressed years two apis provide nearly level function hardware software makers generally respond rapidly changes directx e.g. pixel processor shader requirements directx 9 stream processors directx 10 tessellation directx 11 contrast new features opengl usually implemented first vendors retroactively applied standard shortly establishment direct3d opengl viable graphics libraries circa 1995 microsoft sgi engaged called api wars much argument revolved around api offered superior performance question relevant due high cost dedicated graphics processors time meant consumer market using software renderers implemented microsoft direct3d opengl dos business software autocad dos games id software quake originally optimized run many different graphics chipsets hardware makers 3dlabs member opengl architecture review board made opengl compatible graphics accelerators e.g. glint chip developers john carmack id software optimized products opengl multitasking user environments windows x window system x11 unix-like systems became prevalent relevance hardware faded microsoft marketed direct3d faster based in-house performance comparisons two software libraries performance deficit blamed rigorous specification conformance required opengl perception changed 1996 special interest group graphics interactive techniques siggraph conference time silicon graphics sgi challenged microsoft optimized windows software implementation opengl called cosmogl various demos matched exceeded performance direct3d sgi critical milestone showed opengl poor software rendering performance due microsoft reference opengl implementation due alleged design flaws opengl contrast software rendering 3d api largely irrelevant direct3d opengl applications many directx applications used direct3d software rendering preferring perform software rendering using directdraw facilities access display hardware opengl applications hardware support expected hardware much faster software fallback opengl application constituted rude surprise opengl developer case time sgi demonstrated opengl software rendering performance could competitive direct3d software rendering fast becoming irrelevant due wide availability low cost 3d graphics hardware 1998 even s3 virge graphics accelerator substantially faster fastest pentium ii running direct3d mmx rasterizer substantive modern performance difference arises structure hardware drivers provided hardware developers directx independent hardware vendor ihv drivers kernel-mode drivers installed operating system user-mode part api handled directx runtime provided microsoft opengl however ihv driver divided two parts user-mode part implements opengl api kernel-mode driver called user-mode part issue calling kernel-mode operations user-mode requires performing system call i.e. making cpu switch kernel mode slow operation taking order microseconds complete time cpu perform operations minimizing number times switching operation occurs would improve performance example gpu command buffer full rendering data api could simply store requested rendering call temporary buffer command buffer nearly empty perform switch kernel-mode add set stored commands batch termed marshalling direct3d ihv drivers kernel-mode user-mode code ihv hand chance optimizations occur direct3d runtime user-mode part implements api explicit knowledge driver inner workings effectively support marshalling means every direct3d call sends commands hardware must perform kernel-mode switch takes time order microseconds complete led several behaviors regarding use direct3d important need submitting large batches triangles one function call since opengl ihv drivers user-mode component ihvs ability implement marshalling thus improving performance still kernel-mode switching theoretical maximum number switches opengl implementations simply equal direct3d standard behavior direct3d 10 release included windows vista allows parts drivers run user-mode making possible ihvs implement marshalling thus bringing two back relative performance parity mac os x opengl system similar ihvs implement simpler version opengl api user kernel mode components apple additions runtime provide direct interface user code basic work make ihvs jobs easier introduction mantle amd lead increased discussion modernizing apis updating abstraction concepts used apis reflect graphics processing unit gpu operations microsoft opengl vendors began showcase visions limiting removing altogether driver overhead amount work cpu needs prepare gpu commands march 2014 microsoft presented basic assumptions goals directx12 3d component ready december 2015 opengl vendors took different approach gdc 2014 presented mix features mandatory opengl 4.3 opengl 4.4 already arb extensions show fast paths already present implementations nvidia amd intel later amd donated mantle khronos group api renamed vulkan current cross-platform api dedicated reduce driver overhead better distributing work among multiple cpu gpu cores using unified management compute kernels graphical shaders presentation apitest introduced new tool microbenchmarking specific solutions given problems emphasizing exploration fast paths current apis opengl 4.x direct3d 11 supported gathered results showed modern opengl many times faster direct3d 11 opengl originally designed then-powerful sgi workstations includes many features like stereo rendering imaging subset generally considered limited use games although stereoscopic gaming drawn interest development consumer-level 3d displays api whole contains 250 calls subset perhaps 100 useful game development however official gaming-specific subset ever defined minigl released 3dfx stopgap measure support glquake might served starting point additional features like stencil soon adopted games support full opengl standard continued today workstations consumer machines use architectures operating systems modern versions opengl standard still include features although special workstation-class video cards accelerate opengl extension mechanism probably heavily disputed difference two apis opengl includes mechanism driver advertise extensions api thus introducing new functions blend modes new ways transfer data gpus different texture wrapping parameters allows new functions exposed quickly lead confusion different vendors implement similar extensions different apis many extensions periodically standardized opengl architecture review board arb made core part future opengl revisions hand direct3d specified one vendor microsoft leading consistent api denying access vendor-specific features nvidia ultrashadow technology instance available stock direct3d apis time writing noted direct3d support texture format extensions via fourcc little-known rarely used used s3 texture compression graphics cards added support pixel shaders known opengl fragment shaders direct3d provided one pixel shader 1.1 ps1.1 standard geforce 3 radeon 8500 advertised compatibility opengl functions accessed variety custom extensions theory microsoft approach allows one code path support brands card whereas opengl programmers must write two separate systems reality though limits pixel processing early cards pixel shader 1.1 nothing pseudo-assembly language version nvidia-specific opengl extensions part cards claimed ps 1.1 functionality nvidia built natively radeon 8500 released microsoft released update direct3d included pixel shader 1.4 nothing pseudo-assembly language version ati-specific opengl extensions cards claimed ps 1.4 support ati cards designed precise hardware needed make functionality happen situation existed short time apis second-generation pixel shading cards functioned far similarly architecture evolving toward kind pixel processing conclusion pixel shader 2.0 allowed unified code path direct3d around time opengl introduced arb-approved vertex pixel shader extensions codice_3 codice_4 sets cards supported standard also opengl always seen use professional graphics market directx directx used mostly computer games term professional used refer professional production display graphics computer animated films scientific visualisation opposed games graphics produced end user personal rather professional use currently opengl directx large enough overlap functionality either could used common purposes operating system often main criterion dictating used directx common choice windows opengl nearly everything else esoteric applications still divide applicability two apis accelerated 3d across network connection directly supported opengl opengl extension x window system glx example past many professional graphics cards supported opengl 2010 virtually professional cards work windows platform also support direct3d part change professional graphics market largely unix-based hardware like sgis suns lower cost pc-based systems leading growth windows market segment time providing new market opengl software unix-based consumer systems running linux mac os x principal historical reason opengl dominance professional market performance many professional graphics applications example softimage|3d alias poweranimator originally written iris gl high-end sgi workstations far capable graphically raw cpu power pcs time later many ported opengl even personal computer evolving system powerful enough run professional graphics applications users able run maya example successor alias poweranimator either sgis windows-based personal computers today linux mac os x windows price competition eventually broke sgi dominance market established base opengl software engineers broadening user base opengl apple linux operating systems resulted market directx opengl viable widespread apis reason opengl historic advantage marketing design directx set apis marketed professional graphics applications indeed even designed uses directx api designed low-level high-performance access broadly available lower-performance consumer-priced graphics hardware purpose game development opengl much general purpose 3d api targeting full range graphics hardware low-end commodity graphics cards professional scientific graphics visualization well range average consumer providing features necessarily exclusive specific kind user gaming developers typically n't demanded wide api professional graphics system developers many games n't need overlay planes stencils although n't prevented game developers using available specifically game designers rarely interested pixel invariance demanded certain parts opengl standards conversely highly useful film computer-aided modeling attempt made merge opengl directx sgi microsoft fahrenheit graphics api intended bring together high end ability opengl broad low-level support directx microsoft eventually retreated project never allocated sufficient resources produce part rendering engine move widely held purposed ensure lock-in developers windows-directx platform would lost fahrenheit api became world de facto standard graphics api however fahrenheit led many improvements directx main architect fahrenheit works microsoft directx earliest days 3d accelerated gaming performance reliability key benchmarks several 3d accelerator cards competed dominance software written specific brand graphics card however years opengl direct3d emerged software layers hardware mainly industry support cross-hardware graphics library competition two rose game developer would choose either one early days 3d accelerated gaming vendors supply full opengl driver reason twofold firstly consumer-oriented accelerators implement enough functionality properly accelerate opengl secondly many vendors struggled implement full opengl driver good performance compatibility instead wrote minigl drivers implemented subset opengl enough run glquake later opengl games mostly based quake engine proper opengl drivers became prevalent hardware evolved consumer-oriented accelerators caught sgi systems opengl originally designed would around time directx 6 directx 7 console world proprietary native apis dominant consoles e.g. ps3 providing opengl wrapper around native api original xbox supported direct3d 8.1 native api xbox 360 supports directx9 native api console developers prefer use native apis console maximize performance making opengl direct3d comparisons relevant mostly pc platforms opengl embedded systems called opengl es subset opengl 3d graphics api designed embedded devices various versions smartphone operating systems support opengl es android ios ipad iphone ipod touch maemo nokia n900 symbian opengl es available 6 variants opengl es 1.0 1.1 2.0 3.0 3.1 3.2 release 2.0 removed backward compatibility older variants due extensive programmable pipeline functions available gl es 2.0 fixed-pipeline functions gl es 1.0 1.1 opengl es 3.0 needed new hardware opengl es 2.0 opengl es 3.1 meant software update needing new drivers direct3d mobile direct3d derivative supported windows ce currently windows phone 7 devices use .net framework ui accelerated direct3d mobile 9 adreno 200/205 integrated gpus qualcomm windows phone 8 implements direct3d 11 limited feature level 9_3
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Operating systems
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host monitoring protocol host monitoring protocol hmp obsolete tcp/ip protocol described rfc 869
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Internet protocols
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iphone os 1 iphone os 1 first major release ios apple mobile operating system iphone os 1.1.5 latest last version apple iphone os 1 version ios first iteration touch-centric mobile operating system official name given initial release apple marketing literature simply stated iphone runs version apple desktop operating system macos known mac os x march 6 2008 release iphone software development kit iphone sdk apple named iphone os later went rename ios june 7 2010 succeeded iphone os 2 july 11 2008 iphone os 1.1.3 update cost 19.95 ipod touch users
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Operating systems
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bapp acronyms bapp b.a.p.p bamp b.a.m.p refer set open-source software programs commonly used together run dynamic web sites servers set solution stack open source web platform bapp refers bamp refers two acronyms three major uses operating system freebsd bsd descendant generally regarded reliable robust operating systems accurately report uptime remotely freebsd bsd descendants common free operating system listed netcraft list 50 web servers longest uptime uptime operating systems versions linux determined remotely making top choice among isps hosting providers long uptime also indicates kernel updates deemed necessary installing new kernel requires reboot resets uptime counter system though originators open source programs design work specifically combination become popular low acquisition cost ubiquity components come bundled current bsd distributions particularly deployed isps used combination represent solution stack technologies support application servers stacks include unified application development environments apple computer webobjects java/java ee grails microsoft .net architecture scripting component bapp stack origins cgi web interfaces became popular early 1990s technology allows user web browser execute program web server thereby receive dynamic well static content programmers used scripting languages programs ability manipulate text streams easily efficiently even originate disparate sources reason system designers often referred scripting systems glue languages variants term include
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Programming language topics
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iphone os 2 iphone os 2 second major release ios mobile operating system developed apple inc. successor iphone os 1 first release ios support third-party applications via app store iphone os 2.2.1 final version iphone os 2 succeeded iphone os 3 june 17 2009. iphone os 2.0 became available july 11 2008 release iphone 3g devices running 1.x upgradable version version ios introduces app store making third-party applications available iphone ipod touch prior public release iphone os 2.0 apple held keynote event announce iphone os software development kit sdk developers notable feature iphone os 2 app store feature introduced way install custom applications device via jailbreaking strongly discouraged unsupported apple 500 applications available download launch app store though amount grown dramatically since app store 2 million apps 2016 mail app makeover push-emails provide always-on capability also supports microsoft office attachments well iwork attachments new features including support bcc multiple email delete ability select outgoing email contacts app new home screen icon available ipod touch along release ability search contacts without searched one-by-one well sim contacts import ability new features added maps app iphone os 2.2 software update among features added inclusion google street view directions public transit walking ability display address dropped pin device landscape mode calculator app displays scientific calculator also app icon updated settings ability turn wifi back airplane mode well ability turn on/off location services within app rene ritchie imore said overall iphone firmware 2.0 stunning achievement really puts iphone par apple ii mac one great revolutions modern technology takes beyond simple phone ipod even smartphone makes leading contender next great shift computing however criticized stability issues overall sluggishness macworld said iphone 2.0 software full kind refinements ’ expect second-generation apple product iphone os still ’ perfect wish apple addressed lingering shortcomings ’ welcome step-up already arguably best mobile platform market iphone os 2 cost 9.95 ipod touch users free iphone users
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Operating systems
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iphone os 3 iphone os 3 third major release ios mobile operating system developed apple inc. successor iphone os 2 announced march 17 2009 released june 17 2009 succeeded ios 4 june 21 2010 new version dropped iphone os naming convention iphone os 3 last version use iphone os naming convention iphone os 3 added system-wide cut copy paste dialog bubble allowing users easily move content also introduced spotlight search indexing feature designed help users locate specific information device contacts email messages apps home screen expanded let users add 11 pages showcasing total 180 apps messages app received support mms camera app received support video recording iphone 3gs new voice memos app let users record voice iphone os 3 announced march 17 2009 beta version available developers day iphone os 3 officially released june 17 2009. iphone os 3 introduced cut copy paste bubble dialog users double-tap text paste button would incorporate anything stored device clipboard marked area spotlight system-wide indexing search feature aiming help users search device specific contacts email messages calendar appointments multimedia files apps accessed swiping right home screen iphone os 3 expands maximum number pages home screen 11 total number 180 apps messages app received native support multimedia messaging service mms allowing users send receive messages also contain pictures contacts locations voice recordings video messages camera app introduced video recording iphone 3gs photos app featured new copy button ability delete multiple photos iphone os 3 added voice memos app allowing users record voice upgrading iphone os 3 free iphone upgrading iphone os 3 cost ipod touch users 5 10 depending device purchase date iphone os 3 last ios charge ipod touch users upgrade starting ios 4 ios upgrades became free users including users ipod touch
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Operating systems
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weird machine computer security weird machine computational artifact additional code execution happen outside original specification program closely related concept weird instructions building blocks exploit based crafted input data expected valid input activates normal intended functionality computer program input unexpected program developer may activate unintended functionality weird machine consists unintended functionality programmed selected inputs exploit classical attack taking advantage stack buffer overflow input given vulnerable program crafted delivered becomes executed program code however data areas program memory protected executed directly like input may instead take form pointers pieces existing program code become executed unexpected order generate functionality exploit snippets code used exploit referred gadgets context return-oriented programming interpretation data code weird machine functionality definition outside original program specification reached also proof-carrying code pcc formally proven function certain specific way disparity essentially caused disconnect formal abstract modelling computer program real-world instance influenced events captured original abstraction memory errors power outages two central categories mitigation problems caused weird machine functionality include input validation within software protecting problems arising platform program runs memory errors input validation aims limit scope forms unexpected inputs e.g whitelists allowed inputs software program would end unexpected state interpreting data internally equally importantly secure programming practices protecting buffer overflows make less likely input data becomes interpreted unintended ways lower layers hardware program executed
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Computer security
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openal openal open audio library open open-source cross-platform audio application programming interface api designed efficient rendering multichannel three-dimensional positional audio api style conventions deliberately resemble opengl openal environmental 3d audio library add realism game simulating attenuation degradation sound distance doppler effect change frequency result motion material densities openal aimed originally open standard open-source replacement proprietary generally incompatible one another 3d audio systems eax a3d reference implementation later became proprietary open source implementations openal soft available openal originally developed 2000 loki software help business porting windows games linux demise loki project maintained time free software/open source community implemented nvidia nforce sound cards motherboards hosted largely developed creative technology on-going support apple blue ripple sound via rapture3d openal driver individual open-source developers openal charter says architecture review board arb modeled opengl arb organization ever formed openal specification generally handled discussed via email public mailing list since 1.1 implementation creative turned proprietary last releases free licenses still accessible project subversion source code repository however openal soft widely used open source alternative general functionality openal encoded source objects audio buffers single listener source object contains pointer buffer velocity position direction sound intensity sound listener object contains velocity position direction listener general gain applied sound buffers contain audio data pcm format either 8- 16-bit either monaural stereo format rendering engine performs necessary calculations far distance attenuation doppler effect etc net result end user properly written openal application sounds behave quite naturally user moves three-dimensional space virtual world programmer perspective little additional work required make happen existing opengl-based 3d graphical application unlike opengl specification openal specification includes two subsections api core consisting actual openal function calls alc audio library context api used manage rendering contexts resource usage locking cross platform manner also 'alut audio library utility toolkit library provides higher level 'convenience functions — exactly analogous opengl 'glut order provide additional functionality future openal utilizes extension mechanism individual vendors thereby able include extensions distributions openal commonly purpose exposing additional functionality proprietary hardware extensions promoted arb architecture review board status indicating standard extension maintained backwards compatibility arb extensions prospect added core api period time advanced digital signal processing hardware-accelerated sound effects efx effects extension environmental audio extensions eax used single listener model openal tailored single human user fit artificial intelligence robotic simulations multiple human participants collaborative musical performances cases multiple listener model required openal also fails take account sound propagation delays speed sound used doppler effect distance sound source translates amplitude effect attenuation delay hence openal used time difference arrival calculations unless functionality added separately api available following platforms operating systems android supports opensl es amigaos 3.x 4.x bada blackberry 10 blackberry playbook bsd ios supports core audio irix linux supports alsa oss portaudio pulseaudio mac os 8 mac os 9 mac os x core audio microsoft windows supports directsound windows multimedia api windows multimedia device mmdevice api morphos openbsd solaris qnx aros supported gaming devices instance gamecube playstation 2 playstation 3 xbox xbox 360 wii playstation portable following video games known use openal
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Operating systems
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outline databases following outline provided overview topical guide databases database – organized collection data today typically digital form data typically organized model relevant aspects reality example availability rooms hotels way supports processes requiring information example finding hotel vacancies databases described following database languages – database security – database design – database management system – data warehouse –
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Databases
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decss decss one first free computer programs capable decrypting content commercially produced dvd video disc release decss linux-based computing systems could play encrypted video dvds decss development done without license dvd copy control association cca organization responsible dvd copy protection—namely content scramble system css used commercial dvd publishers release decss resulted norway criminal trial subsequent acquittal one authors decss dvd cca launched numerous lawsuits united states effort stop distribution software decss devised three people two remain anonymous released internet mailing list livid october 1999 one known author trio norwegian programmer jon lech johansen whose home raided 2000 norwegian police still teenager time put trial norwegian court violating norwegian criminal code section 145 faced possible jail sentence two years large fines acquitted charges early 2003 5 march 2003 norwegian appeals court ruled johansen would retried court said arguments filed prosecutor additional evidence merited another trial 22 december 2003 appeals court agreed acquittal 5 january 2004 norway økokrim economic crime unit decided pursue case program first released 6 october 1999 johansen posted announcement decss 1.1b closed source windows-only application dvd ripping livid-dev mailing list source code leaked end month first release decss preceded weeks program called dod dvd speed ripper group called drinkordie also faced later raids piracy prosecutions jail one member even extradited australia usa prosecution despite never set foot n't include source code apparently work dvds drink die reportedly disassembled object code xing dvd player obtain player key group wrote decss including johansen came call masters reverse engineering may obtained information drink die css decryption source code used decss mailed derek fawcus decss released decss source code leaked fawcus noticed decss included css-auth code violation gnu gpl johansen made aware contacted fawcus solve issue granted license use code decss non-gpl terms 22 january 2004 dvd cca dropped case jon johansen decss program collaborative project johansen wrote graphical user interface transcripts borgarting court appeal published norwegian newspaper verdens gang contain following description process led release decss internet relay chat henceforth irc jon lech johansen made contact like-minded people seeking develop dvd-player linux operating system 11 september 1999 conversation mdx encryption algorithm css could found using poorly secured software-based dvd-player conversation jon lech johansen mdx 22 september mdx informs nomad found code css decryption mdx would send code jon lech johansen nomad allegedly found decryption algorithm so-called reverse engineering xing dvd-player decryption keys less openly accessible information made possible mdx create code css_scramble.cpp retrieved chat logs dated 4 november 1999 25 november 1999 appears nomad carried reverse engineering process xing player characterized illegal case presented high court known jon lech johansen 4 november 1999 regarding authentication code high court takes basis nomad obtained code electronic mailing list livid linux video internet created derek fawcus appears livid posting dated 6 october 1999 derek fawcus date read decss source code compared appears creators decss taken derek fawcus code almost verbatim alteration removal derek fawcus copyright header paragraph containing commentaries change function names name code css_auth.cpp high court takes basis program jon lech johansen later programmed graphical user interface consisted nomad decryption algorithm derek fawcus authentication package creation graphical user interface made program accessible also users without special knowledge programming program published internet first time 6 october 1999 jon lech johansen tested movie matrix downloaded approximately 2.5 200 megabytes movie hard drive computer file film fragment jon lech johansen saved computer release decss source code made css algorithm available public scrutiny soon found susceptible brute force attack quite different decss encryption 40-bit use keys high-end home computer 1999 running optimized code could brute-force within 24 hours modern computers brute-force seconds less programmers around world created hundreds programs equivalent decss merely demonstrate trivial ease system could bypassed others add dvd support open source movie players licensing restrictions css make impossible create open source implementation official channels closed source drivers unavailable operating systems users need decss watch even legally obtained movies first legal threats sites hosting decss beginning decss mirroring campaign began early november 1999 universal v. reimerdes preliminary injunction dvd copy control association inc. v. bunner followed soon january 2000 response threats program also called decss unrelated function developed program used strip cascading style sheets tags html pages one case school removed student webpage included copy program mistaking original decss program received great deal negative media attention css stripping program specifically created bait mpaa manner protest legislation prohibits publication copy protection circumvention code countries implement wipo copyright treaty united states digital millennium copyright act devised clever ways distributing descriptions decss algorithm steganography various internet protocols t-shirts dramatic readings midi files haiku poem decss haiku even so-called illegal prime number lawrence lessig future ideas 2001 p. 187-190 freely available
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Computer security
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chris tomic chris tomic born 1978 german computer scientist inventor entrepreneur reality tv personality featured several television shows mostly german news channel n-tv television studies germany heinrich-heine-universität düsseldorf started developing technologies internet mobile industry düsseldorf company novadoc gmbh 2001 tomic created ucp protocol set standard worldwide first delivery binary messages mobile handsets operator-logos monophonic ringtones 1998 executive director company novadoc gmbh focused research development secure mobile payments micropayments sms mobile payments 2001 became cto company monstermob ltd uk 2003 monstermob ltd floated london stock exchange opening market capitalisation £32m spanish internet firm lanetro zed bought majority 53 stake business agreement mean lanetro zed monstermob ltd together become world largest company mobile value-added services mvas market terms revenue enlarged company operating 31 countries around world employing 1,200 staff
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Programming language topics
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rasmus lerdorf rasmus lerdorf born 22 november 1968 danish-canadian programmer co-authored inspired php scripting language authoring first two versions language participated development later versions led group developers including jim winstead later created blo.gs stig bakken shane caraveo andi gutmans zeev suraski continues contribute project lerdorf born disko island greenland moved denmark early years lerdorf family moved canada denmark 1980 later moved king city ontario 1983 graduated king city secondary school 1988 1993 graduated university waterloo bachelor applied science systems design engineering contributed apache http server added limit clause msql dbms variant limit clause already around decade mainframe relational database management systems like oracle rdb running vax/vms formerly digital equipment corporation apparently yet picked emerging pc-based databases later adapted several sql-compatible dbms released first version php 1995 september 2002 november 2009 lerdorf employed yahoo inc. infrastructure architecture engineer 2010 joined wepay order develop application programming interface throughout 2011 roving consultant startups 22 february 2012 announced twitter joined etsy july 2013 rasmus joined jelastic senior advisor help creation new technology lerdorf frequent speaker open source conferences around world keynote presentation oscms 2007 presented security vulnerability projects represented conference year lerdorf also appeared wearedevelopers conferences 2017 2019 making speech history php new php 7 release 2017 25 years php.. 2003 lerdorf named mit technology review tr100 one top 100 innovators world age 35
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Programming language topics
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silc protocol silc secure internet live conferencing protocol protocol provides secure synchronous conferencing services much like irc internet silc protocol divided three main parts silc key exchange ske protocol silc authentication protocol silc packet protocol silc protocol additionally defines silc commands used manage silc session silc provides channels groups nicknames private messages common features however silc nicknames contrast many protocols e.g irc unique user able use nickname even one already use real identification protocol performed unique client id silc protocol uses overcome nickname collision problem present many protocols messages sent silc network binary allowing contain type data including text video audio multimedia data ske protocol used establish session key security parameters protecting silc packet protocol ske based diffie-hellman key exchange algorithm form asymmetric cryptography exchange protected digital signatures silc authentication protocol performed successful ske protocol execution authenticate client and/or server authentication may based passphrase digital signatures successful gives access relevant silc network silc packet protocol intended secure binary packet protocol assuring content packet consisting packet header packet payload secured authenticated packets secured using algorithms based symmetric cryptography authenticated using message authentication code algorithm hmac silc channels groups protected using symmetric channel keys optionally possible digitally sign channel messages also possible protect messages privately generated channel key previously agreed upon channel members private messages users silc network protected session keys however possible execute ske protocol two users use generated key protect private messages private messages may optionally digitally signed messages secured key material generated ske protocol previously agreed upon key material example passphrases silc provides security even silc server may compromised silc designed pekka riikonen 1996 1999 first released public summer 2000 client server written protocol specifications proposed ultimately request publication denied june 2004 iesg rfc published date present time several clients advanced official silc client irssi plugin silc protocol also integrated popular pidgin instant messaging client gui clients silky colloquy silky client put hold abandoned 18th july 2007 due inactivity several years latest news silky website client completely rewritten 2008 three silc protocol implementations written silc clients use libsilc part silc toolkit silc toolkit dual-licensed distributed gnu general public license gpl revised bsd license described silc faq chats secured generation symmetric encryption keys keys generated somewhere occurs server means chats might compromised server compromised version man-in-the-middle attack solution offered chat members generate public-private keypair asymmetric encryption private key shared chat members done band public key used encrypt messages channel approach still open compromise one members chat private key compromised share key another without agreement group silc uses similar pattern irc global silc network many small independent networks consisting one several servers although claimed silc scale better many servers single network original network called silcnet silc.silcnet.org round-robin however may 2014 one active though unstable server four several public networks known external links section however also shut due declining popularity silc
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Internet protocols
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transformation language transformation language computer language designed transform input text certain formal language modified output text meets specific goal program transformation systems stratego/xt txl tom dms asf+sdf transformation languages major component transformation languages systems driven declarative descriptions structure input text typically grammar allowing applied wide variety formal languages documents macro languages kind transformation languages transform meta language specific higher programming language like java c++ fortran lower-level assembly language model-driven engineering technical space model transformation languages mtls take input models conforming given metamodel produce output models conforming different metamodel example language qvt omg standard also low-level languages lx family implemented bootstrapping method l0 language may considered assembler transformation languages also high-level graphical language built upon lx called mola number xml transformation languages include tritium xslt xquery stx fxt xduce cduce haxml xmlambda flexml concepts languages typical transforms
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Programming language topics
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clearos clearos also known clearos system formerly clarkconnect operating system marketed software company clearcenter based centos red hat enterprise linux designed use small medium enterprises network gateway network server web-based administration interface positioned alternative windows small business server clearos succeeds clarkconnect software built clearfoundation support services purchased clearcenter clearos 5.1 removes previous limitations mail dmz multiwan functions clearos 6.1 release distribution full-featured operating system gateway network servers built source packages red hat enterprise linux features include
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Computer security
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sip trunking sip trunking enables end point ’ pbx phone exchange system send receive calls via internet sip applied signalling protocol multiple real-time application sip trunk able control voice video messaging applications also voice internet protocol voip technology streaming media service based session initiation protocol sip internet telephony service providers itsps deliver telephone services unified communications customers equipped sip-based ip pbx unified communications facilities unified communications applications provide voice video streaming media applications desktop sharing web conferencing shared whiteboard architecture sip trunking provides partitioning unified communications network two different domains expertise interconnection two domains must occur sip trunk interconnection two domains created transport via internet protocol ip involves setting specific rules regulations well ability handle services protocols fall name sip trunking itsp responsible applicable regulatory authority regarding following law obligations public domain private domain instead nature subject particular constraints law may either responsibility itsp end user enterprise third party provides voice services company domain elements perform characteristic features requested domain particular result part front-end network customer logically divided two levels private domain consists three levels
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Internet protocols
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joinup collaboration platform joinup collaboration platform created european commission funded european union via interoperability solutions public administrations programme isa programme joinup launched 9 december 2011 replaced open source observatory repository osor.eu semantic interoperability centre europe semic.eu communities funded isa programme two became joinup initial communities site aims let public administrations promote e-government systems specifically offers meeting place collaborative working environment development interoperability joinup hosts communities practice community common assessment method standards specifications camss community national interoperability frameworks observatory nifo platform also raises awareness free open source software semantic interoperability public sector joinup offers catalogue open source software interoperability assets models interoperability maturity model imm target audience includes using developing implementing e-government systems site focuses european public sector projects open others platform three main functions site offers software development tools including software repository apache subversion issue tracker joinup provides access federation catalogue hosted public administrations eu member states standardisation bodies european committee standardization cen european telecommunications standards institute etsi joinup also used european commission directorate general informatics make available applications examples include circabc document management system open e-prior tool help manage electronic procurement online collection software eci help organisations gather signatures support request european commission propose legislation december 2014 isa programme added epractice community joinup platform epractice offers services professional community egovernment einclusion ehealth practitioners january 2015 opengovernment community added ec directorate general communications networks content technology detailed list potential services someone receives registering platform found list software contributions made community new version joinup currently developed one features joinup platform creation maven repositories new projects disappear joinup platform powered tailored version drupal content management framework version 6 downloaded joinup web site latest version 1.7.2 released march 15 2015 software like platform powers suitable used application lifecycle management tool software forge source code past versions found development platform done hosts running debian linux joinup platform runs 10 hosts ec datacentre luxembourg includes load balancer network-attached storage reverse-proxy main part platform three red hat linux hosts running apache webserver drupal fourth linux host running apache tomcat java server apache solr search engine apache maven build automation tools fifth linux host running apache subversion software versioning revisioning system sixth linux host running mysql relational database system seventh gnu mailman platform software used offer similar services involving public administrations regions countries australia new zealand openray platform piloted since june 2012 open technology foundation otf research organisation supporting government sector research evaluation trialling uptake open technologies standards methods 21 november 2013 semantic services federated show openray repository also 21 november 2013 government south australia announced would start piloting internal version joinup platform software test use ec open e-prior south australia test use joinup sharing re-use retrieved 2013-11-24 aim improve collaboration procurement activities openroad similar collaboration platform begun vietnam ministry science technology january 2013 joinup federation similar projects french adullact started 2002 association des développeurs et utilisateurs de logiciels libres pour les administrations et les collectivités territoriales association developers users free software governments local authorities adullact actually inspiration ec's open source observatory repository examples would spanish centro de transferencia de tecnología centre technology transfer la forja de guadalinex hosted junta de andalucia platform could also compared national information exchange model niem xml-based information exchange framework united states however niem designed develop disseminate support information exchange standards processes enable jurisdictions automate information sharing ec joinup sharing information technology joinup might even compared comprehensive knowledge archive network ckan however focuses software packages semantic assets storage distribution data spreadsheets contents databases
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Operating systems
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veritas file system veritas file system vxfs called jfs onlinejfs hp-ux extent-based file system originally developed veritas software oem agreement vxfs used primary filesystem hp-ux operating system on-line defragmentation resize support turned via license known onlinejfs also supported aix linux solaris opensolaris sinix/reliant unix unixware sco openserver vxfs originally developed unix system laboratories vxfs packaged part veritas storage foundation also includes veritas volume manager according vendor first commercial journaling file system claim taken two ways i.e. first implementation journaling file system commercial context first file system available unbundled product dan koren cited one original developers vxfs notes mailing list finished release 1.0 one year later starting development vxfs contract corporation 1990 sources agree product first released 1991 internet widely available early 1990s getting new file system deployed unix like operating systems difficult one- two-year delay release commercialization file system unusual on-disk layout vxfs versioned upgradeable file system mounted file system gone ten versions vxfs file system run single instance mode parallel access cluster mode parallel mode allows multiple servers also known cluster nodes simultaneously access file system run mode vxfs referred veritas cluster file system cluster file system provides cache coherency posix compliance across nodes data changes atomically seen cluster nodes simultaneously cluster file system shares binaries on-disk layout single instance vxfs moving cluster single instance mode straightforward
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Computer file systems
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message signaled interrupts message signaled interrupts msi alternative in-band method signaling interrupt using special in-band messages replace traditional out-of-band assertion dedicated interrupt lines complex implement device message signaled interrupts significant advantages pin-based out-of-band interrupt signaling message signaled interrupts supported pci bus since version 2.2 later available pci express bus non-pci architectures also use message signaled interrupts traditionally device interrupt line pin asserts wants signal interrupt host processing environment traditional form interrupt signaling out-of-band form control signaling since uses dedicated path send control information separately main data path msi replaces dedicated interrupt lines in-band signaling exchanging special messages indicate interrupts main data path particular msi allows device write small amount interrupt-describing data special memory-mapped i/o address chipset delivers corresponding interrupt processor common misconception msi allows device send data processor part interrupt data sent part memory write transaction used chipset determine interrupt trigger processor data available device communicate additional information interrupt handler example pci express separate interrupt pins instead uses special in-band messages allow pin assertion deassertion emulated non-pci architectures also use msi another example hp gsc devices interrupt pins generate interrupts writing directly processor interrupt register memory space hypertransport protocol also supports msi complex implement device message signaled interrupts significant advantages pin-based out-of-band interrupt signaling mechanical side fewer pins makes simpler cheaper reliable connector advantage standard pci connector pci express takes advantage savings msi increases number interrupts possible conventional pci limited four interrupts per card shared among cards using one message signaled interrupts allow dozens interrupts per card useful also slight performance advantage software pin-based interrupt could race posted write memory pci device would write data memory send interrupt indicate dma write complete however pci bridge memory controller might buffer write order interfere memory use interrupt could arrive dma write complete processor could read stale data memory prevent race interrupt handlers required read device ensure dma write finished read moderate performance penalty msi write pass dma write race eliminated pci defines two optional extensions support message signaled interrupts msi msi-x pci express compatible legacy interrupts software level requires msi msi-x msi first defined pci 2.2 permits device allocate 1 2 4 8 16 32 interrupts device programmed address write generally control register interrupt controller 16-bit data word identify interrupt number added data word identify interrupt platforms windows use 32 interrupts use 16 interrupts msi-x first defined pci 3.0 permits device allocate 2048 interrupts single address used original msi found restrictive architectures particular made difficult target individual interrupts different processors helpful high-speed networking applications msi-x allows larger number interrupts gives one separate target address data word devices msi-x necessarily support 2048 interrupts optional features msi 64-bit addressing interrupt masking also mandatory msi-x intel systems lapic must enabled pci pci express msi/msi-x work even uniprocessor single core systems systems msis handled writing interrupt vector directly lapic processor/core needs service interrupt intel lapics 2009 supported 224 msi-based interrupts according 2009 intel benchmark using linux using msi reduced latency interrupts factor almost three compared i/o apic delivery motherboard implementations particularly among pci pci-x bridges non-functional msi support amd-8131 serverworks pci express chipsets among problems least versions linux also observed motherboards nvidia nforce chipsets broken msi support result nvidia enabled msi support graphics card drivers first time many users nforce-based motherboards complained instability eventually traced back msi implementation motherboard users complained errors ranging relatively harmless unresponsive gpus windows vista 7 eventually recover usb devices intermittently ceasing work linux gpu tasked heavy workloads hard freezes blue screens kernel panics platforms later versions drivers blacklist platforms activate msi microsoft family operating systems windows vista later versions support msi msi-x support added longhorn development cycle around 2004 msi supported earlier versions like windows xp windows server 2003 solaris express release 6/05 added support msi msi-x part new device driver interface ddi interrupt framework freebsd 6.3 7.0 added support msi msi-x openbsd 5.0 added support msi 6.0 added support msi-x linux gained support msi msi-x around 2003 linux kernel versions 2.6.20 known serious bugs limitations implementation msi/msi-x haiku gained support msi around 2010 msi-x support added later 2013 netbsd 8.0 added support msi msi-x
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Computer architecture
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ms-dos 4.0 multitasking ms-dos 4.0 multitasking release ms-dos developed microsoft based ms-dos 2.0 lack interest oems particularly ibm previously gave microsoft multitasking code ibm pc dos included topview led released scaled-back form sometimes referred european ms-dos 4.0 primarily used confused pc dos 4.00 ms-dos 4.01 later contain multi-tasking features apricot computers pre-announced ms-dos 4.0 early 1986 microsoft demonstrated september year paris trade show however european oems international computers limited icl actually licensed releases software particular ibm declined product concentrating instead improvements ms-dos 3.x new joint development microsoft produce os/2 result project scaled back features promised particular oems delivered september 1987 version multi-tasking ms-dos 4.1 reported developed icl drs professional workstation pws releases made contracts fulfilled july 1988 ibm announced ibm dos 4.0 unrelated product continuing dos 3.3 3.4 leading initial conjecture microsoft might release different version number however microsoft eventually released ms-dos 4.0 ms-dos 4.01 following quickly fix issues many reported well minor improvements support new executable file format key feature release support preemptive multitasking use protected mode available 80386 processors allowed specially-written programs continue executing background mode access user input output returned foreground os reported include time-sliced scheduler interprocess communication via pipes shared memory limited form multitasking considered useful server rather workstation environment particularly coupled ms-net 2.0 released simultaneously limitations ms-dos 3.0 remained including inability use memory 640 kb contributed product lack adoption particularly light need write programs specifically targeted new environment int 21h/ah=87h used distinguish multitasking ms-dos 4.x later ms-dos/pc dos 4.x issues microsoft president jon shirley described specialized version went far saying maybe n't called dos 4.0 although clear whether always intention enthusiastic response oems would resulted true successor dos 3.x marketing positioned additional option dos 3.x workstations xenix higher-end servers multiuser systems
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Operating systems
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graph reduction computer science graph reduction implements efficient version non-strict evaluation evaluation strategy arguments function immediately evaluated form non-strict evaluation also known lazy evaluation used functional programming languages technique first developed chris wadsworth 1971 simple example evaluating arithmetic expression follows reduction sequence employs strategy known outermost tree reduction expression evaluated using innermost tree reduction yielding reduction sequence notice reduction order made explicit addition parentheses expression could also simply evaluated right left addition associative operation represented tree expression looks like term tree reduction comes represented tree think innermost reduction working bottom outermost works top expression also represented directed acyclic graph allowing sub-expressions shared trees outermost innermost reduction also applies graphs hence graph reduction evaluation outermost graph reduction proceed follows notice evaluation requires four steps outermost graph reduction referred lazy evaluation innermost graph reduction referred eager evaluation combinator graph reduction fundamental implementation technique functional programming languages program converted combinator representation mapped directed graph data structure computer memory program execution consists rewriting parts graph reducing move towards useful results concept graph reduction allows evaluated values shared first developed chris wadsworth 1971 ph.d. dissertation dissertation cited peter henderson james h. morris jr. 1976 paper “ lazy evaluator ” introduced notion lazy evaluation 1976 david turner incorporated lazy evaluation sasl using combinators sasl early functional programming language first developed turner 1972
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Programming language topics
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ibm 4767 ibm 4767 pcie cryptographic coprocessor hardware security module hsm includes secure cryptoprocessor implemented high-security tamper resistant programmable pcie board specialized cryptographic electronics microprocessor memory random number generator housed within tamper-responding environment provide highly secure subsystem data processing cryptography performed sensitive key material never exposed outside physical secure boundary clear format ibm 4767 validated fips pub 140-2 level 4 highest level certification achievable commercial cryptographic devices ibm 4767 data sheet describes coprocessor detail ibm supplies two cryptographic-system implementations toolkits custom application development also available applications may include financial pin transactions bank-to-clearing-house transactions emv transactions integrated circuit chip based credit cards general-purpose cryptographic applications using symmetric key algorithms hashing algorithms public key algorithms operational keys symmetric rsa private generated coprocessor saved either keystore file application memory encrypted master key coprocessor coprocessor identical master key use keys performance benefits include incorporation elliptic curve cryptography ecc format preserving encryption fpe hardware ibm supports 4767 certain ibm z ibm power systems x86 servers linux microsoft windows april 2016 ibm 4767 superseded ibm 4765 discontinued ibm 4767 supported platforms listed successor 4767 ibm 4768 introduced ibm z called crypto express6s cex6s available feature code 0893 links point various relevant cryptographic standards iso 13491 secure cryptographic devices https //www.iso.org/standard/61137.html iso 9564 pin security https //www.iso.org/standard/68669.html ansi x9.24 part 1 key management using symmetric techniques https //webstore.ansi.org/recorddetail.aspx sku=ansi+x9.24-1-2017 ansi x9.24 part 2 key management using asymmetric techniques https //webstore.ansi.org/recorddetail.aspx sku=ansi+x9.24-2-2016 fips 140-2 https //nvlpubs.nist.gov/nistpubs/fips/nist.fips.140-2.pdf
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Computer security
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random-access memory random-access memory ram form computer memory read changed order typically used store working data machine code random-access memory device allows data items read written almost amount time irrespective physical location data inside memory contrast direct-access data storage media hard disks cd-rws dvd-rws older magnetic tapes drum memory time required read write data items varies significantly depending physical locations recording medium due mechanical limitations media rotation speeds arm movement ram contains multiplexing demultiplexing circuitry connect data lines addressed storage reading writing entry usually one bit storage accessed address ram devices often multiple data lines said 8-bit 16-bit etc devices today technology random-access memory takes form integrated circuit ic chips mos metal-oxide-semiconductor memory cells ram normally associated volatile types memory dram modules stored information lost power removed although non-volatile ram also developed types non-volatile memories exist allow random access read operations either allow write operations kinds limitations include types rom type flash memory called nor-flash two main types volatile random-access semiconductor memory static random-access memory sram dynamic random-access memory dram commercial uses semiconductor ram date back 1965 ibm introduced sp95 sram chip system/360 model 95 computer toshiba used dram memory cells toscal bc-1411 electronic calculator based bipolar transistors commercial mos memory based mos transistors developed late 1960s first commercial dram ic chip intel 1103 introduced october 1970 synchronous dynamic random-access memory sdram later debuted samsung km48sl2000 chip 1992 early computers used relays mechanical counters delay lines main memory functions ultrasonic delay lines could reproduce data order written drum memory could expanded relatively low cost efficient retrieval memory items required knowledge physical layout drum optimize speed latches built vacuum tube triodes later discrete transistors used smaller faster memories registers registers relatively large costly use large amounts data generally dozen hundred bits memory could provided first practical form random-access memory williams tube starting 1947 stored data electrically charged spots face cathode ray tube since electron beam crt could read write spots tube order memory random access capacity williams tube hundred around thousand bits much smaller faster power-efficient using individual vacuum tube latches developed university manchester england williams tube provided medium first electronically stored program implemented manchester baby computer first successfully ran program 21 june 1948 fact rather williams tube memory designed baby baby testbed demonstrate reliability memory magnetic-core memory invented 1947 developed mid-1970s became widespread form random-access memory relying array magnetized rings changing sense ring magnetization data could stored one bit stored per ring since every ring combination address wires select read write access memory location sequence possible magnetic core memory standard form computer memory system displaced solid-state mos metal-oxide-silicon semiconductor memory integrated circuits ics early 1970s prior development integrated read-only memory rom circuits permanent read-only random-access memory often constructed using diode matrices driven address decoders specially wound core rope memory planes semiconductor memory began 1960s bipolar memory used bipolar transistors improved performance could compete lower price magnetic core memory invention mosfet metal-oxide-semiconductor field-effect transistor also known mos transistor mohamed atalla dawon kahng bell labs 1959 led development mos semiconductor memory john schmidt fairchild semiconductor 1964 addition higher performance mos memory cheaper consumed less power magnetic core memory development silicon-gate mos integrated circuit ic technology federico faggin fairchild 1968 enabled production mos memory chips mos memory overtook magnetic core memory dominant memory technology early 1970s integrated bipolar static random-access memory sram invented robert h. norman fairchild semiconductor 1963 followed development mos sram john schmidt fairchild 1964 commercial use sram began 1965 ibm introduced sp95 memory chip system/360 model 95 dynamic random-access memory dram allowed replacement 4 6-transistor latch circuit single transistor memory bit greatly increasing memory density cost volatility data stored tiny capacitance transistor periodically refreshed every milliseconds charge could leak away toshiba toscal bc-1411 electronic calculator introduced 1965 used form capacitive bipolar dram storing 180-bit data discrete memory cells consisting germanium bipolar transistors capacitors 1967 robert h. dennard ibm filed patent single-transistor mos dram memory cell using mosfet transistor first commercial dram ic chip intel 1103 manufactured 8µm mos process capacity 1kb released 1970 synchronous dynamic random-access memory sdram developed samsung electronics first commercial sdram chip samsung km48sl2000 capacity 16mb introduced samsung 1992 mass-produced 1993 first commercial ddr sdram double data rate sdram memory chip samsung 64mb ddr sdram chip released june 1998 gddr graphics ddr form ddr sgram synchronous graphics ram first released samsung 16mb memory chip 1998 two widely used forms modern ram static ram sram dynamic ram dram sram bit data stored using state six-transistor memory cell form ram expensive produce generally faster requires less dynamic power dram modern computers sram often used cache memory cpu dram stores bit data using transistor capacitor pair together comprise dram cell capacitor holds high low charge 1 0 respectively transistor acts switch lets control circuitry chip read capacitor state charge change form memory less expensive produce static ram predominant form computer memory used modern computers static dynamic ram considered volatile state lost reset power removed system contrast read-only memory rom stores data permanently enabling disabling selected transistors memory altered writeable variants rom eeprom flash memory share properties rom ram enabling data persist without power updated without requiring special equipment persistent forms semiconductor rom include usb flash drives memory cards cameras portable devices solid-state drives ecc memory either sram dram includes special circuitry detect and/or correct random faults memory errors stored data using parity bits error correction codes general term ram refers solely solid-state memory devices either dram sram specifically main memory computers optical storage term dvd-ram somewhat misnomer since unlike cd-rw dvd-rw need erased reuse nevertheless dvd-ram behaves much like hard disc drive somewhat slower memory cell fundamental building block computer memory memory cell electronic circuit stores one bit binary information must set store logic 1 high voltage level reset store logic 0 low voltage level value maintained/stored changed set/reset process value memory cell accessed reading sram memory cell type flip-flop circuit usually implemented using fets means sram requires low power accessed expensive low storage density second type dram based around capacitor charging discharging capacitor store 1 0 cell however charge capacitor slowly leaks away must refreshed periodically refresh process dram uses power achieve greater storage densities lower unit costs compared sram useful memory cells must readable writeable within ram device multiplexing demultiplexing circuitry used select memory cells typically ram device set address lines a0 ... combination bits may applied lines set memory cells activated due addressing ram devices virtually always memory capacity power two usually several memory cells share address example 4 bit 'wide ram chip 4 memory cells address often width memory microprocessor different 32 bit microprocessor eight 4 bit ram chips would needed often addresses needed provided device case external multiplexors device used activate correct device accessed one read over-write data ram many computer systems memory hierarchy consisting processor registers on-die sram caches external caches dram paging systems virtual memory swap space hard drive entire pool memory may referred ram many developers even though various subsystems different access times violating original concept behind random access term ram even within hierarchy level dram specific row column bank rank channel interleave organization components make access time variable although extent access time rotating storage media tape variable overall goal using memory hierarchy obtain highest possible average access performance minimizing total cost entire memory system generally memory hierarchy follows access time fast cpu registers top slow hard drive bottom many modern personal computers ram comes easily upgraded form modules called memory modules dram modules size sticks chewing gum quickly replaced become damaged changing needs demand storage capacity suggested smaller amounts ram mostly sram also integrated cpu ics motherboard well hard-drives cd-roms several parts computer system addition serving temporary storage working space operating system applications ram used numerous ways modern operating systems employ method extending ram capacity known virtual memory portion computer hard drive set aside paging file scratch partition combination physical ram paging file form system total memory example computer 2 gb ram 1 gb page file operating system 3 gb total memory available system runs low physical memory swap portions ram paging file make room new data well read previously swapped information back ram excessive use mechanism results thrashing generally hampers overall system performance mainly hard drives far slower ram software partition portion computer ram allowing act much faster hard drive called ram disk ram disk loses stored data computer shut unless memory arranged standby battery source sometimes contents relatively slow rom chip copied read/write memory allow shorter access times rom chip disabled initialized memory locations switched block addresses often write-protected process sometimes called shadowing fairly common computers embedded systems common example bios typical personal computers often option called “ use shadow bios ” similar enabled functions rely data bios ’ rom instead use dram locations also toggle shadowing video card rom rom sections depending system may result increased performance may cause incompatibilities example hardware may inaccessible operating system shadow ram used systems benefit may hypothetical bios used booting favor direct hardware access free memory reduced size shadowed roms several new types non-volatile ram preserve data powered development technologies used include carbon nanotubes approaches utilizing tunnel magnetoresistance amongst 1st generation mram 128 kib bytes chip manufactured 0.18 µm technology summer 2003 june 2004 infineon technologies unveiled 16 mib 16 × 2 bytes prototype based 0.18 µm technology two 2nd generation techniques currently development thermal-assisted switching tas developed crocus technology spin-transfer torque stt crocus hynix ibm several companies working nantero built functioning carbon nanotube memory prototype 10 gib 10 × 2 bytes array 2004 whether technologies eventually take significant market share either dram sram flash-memory technology however remains seen since 2006 solid-state drives based flash memory capacities exceeding 256 gigabytes performance far exceeding traditional disks become available development started blur definition traditional random-access memory disks dramatically reducing difference performance kinds random-access memory ecoram specifically designed server farms low power consumption important speed memory wall growing disparity speed cpu memory outside cpu chip important reason disparity limited communication bandwidth beyond chip boundaries also referred bandwidth wall 1986 2000 cpu speed improved annual rate 55 memory speed improved 10 given trends expected memory latency would become overwhelming bottleneck computer performance cpu speed improvements slowed significantly partly due major physical barriers partly current cpu designs already hit memory wall sense intel summarized causes 2005 document first chip geometries shrink clock frequencies rise transistor leakage current increases leading excess power consumption heat ... secondly advantages higher clock speeds part negated memory latency since memory access times able keep pace increasing clock frequencies third certain applications traditional serial architectures becoming less efficient processors get faster due so-called von neumann bottleneck undercutting gains frequency increases might otherwise buy addition partly due limitations means producing inductance within solid state devices resistance-capacitance rc delays signal transmission growing feature sizes shrink imposing additional bottleneck frequency increases n't address rc delays signal transmission also noted clock rate versus ipc end road conventional microarchitectures projected maximum 12.5 average annual cpu performance improvement 2000 2014 different concept processor-memory performance gap addressed 3d integrated circuits reduce distance logic memory aspects apart 2d chip memory subsystem design requires focus gap widening time main method bridging gap use caches small amounts high-speed memory houses recent operations instructions nearby processor speeding execution operations instructions cases called upon frequently multiple levels caching developed deal widening gap performance high-speed modern computers relies evolving caching techniques prevent loss processor performance takes less time perform computation initiated complete 53 difference growth speed processor speeds lagging speed main memory access solid-state hard drives continued increase speed ~400 mb/s via sata3 2012 ~3 gb/s via nvme/pcie 2018 closing gap ram hard disk speeds although ram continues order magnitude faster single-lane ddr4 3200 capable 25 gb/s modern gddr even faster fast cheap non-volatile solid state drives replaced functions formerly performed ram holding certain data immediate availability server farms 1 terabyte ssd storage 200 1tb ram would cost thousands dollars despite speed ram still necessity efficient computation large local data sets analytics machine learning though producing graphics video games vr
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Computer architecture
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taclane taclane short tactical fastlane tactical local area network encryption family inline network encryptors ine developed manufactured general dynamics mission systems meet national security agency nsa requirements high assurance internet protocol encryptor haipe version 4.1 nov 2013 taclane devices type 1 key-agile in-line network encryptors provide network communications security internet protocol ip asynchronous transfer mode atm networks individual user enclaves users security level typically deployed department defense dod tactical strategic networks government agencies contractors taclanes allow users communicate securely legacy networks mobile subscriber equipment packet network non-secure internet protocol router network niprnet secret internet protocol router network siprnet emerging atm networks taclanes provide encryption ip datagram traffic atm traffic ip datagrams encapsulated atm cells support variety ip atm mixed network configurations taclanes used overlay secure virtual private network top existing public and/or private network infrastructures taclane-micro introduced became certified nsa 2007 protect classified information top secret 2014 announced general dynamics c4 systems general dynamics mission systems delivered 100,000 taclane-micro encryptors u.s. navy space naval warfare systems command spawar taclane-c100 designated suite b cryptographic high value product chvp encryptor certified national security agency nsa suite b device secure network communications secret level 2012 certification makes c100 non-controlled cryptographic item cci taclane-10g encryptor haipe encryptor offer simultaneous ip ethernet capabilities providing 10 gbit/s throughput speed 10g secures information classified top secret sci government commercial networks encryptor became certified national security agency nsa 2015 allowed u.s government agencies order 10g encryptor taclane-1g ruggedized tactical strategic environments encryptor became nsa certified secure information classified top secret sci 2013 taclane-flex became certified nsa secure information top secret/sci level 2017 taclane-nano encryptor works integrate flyaway kits deployable systems well facilitates communications intelligence surveillance reconnaissance dismounted tactical forward deployment covert special operations encryptor certified nsa yet general dynamics mission systems announced end production product december 2015 general dynamics mission systems announced end life eol product
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Computer security
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snapforce crm snapforce crm comprehensive customer relationship management crm saas application developed snapforce.com primary use case customer management sales automation although also configured telephony support additional software components include customer databases customer interaction tracking reporting workflow automation snapforce crm configured handle inbound outbound calling calls logged prospect customer record automatically real time may 2014 company became first crm software provider offer telephony services native feature snapforce crm recognized one ten top players customer relationship management market report 2015
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Distributed computing architecture
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program lifecycle phase program lifecycle phases stages computer program undergoes initial creation deployment execution phases edit time compile time link time distribution time installation time load time run time lifecycle phases necessarily happen linear order intertwined various ways example modifying program software developer may need repeatedly edit compile install execute computer ensure sufficient quality distributed users copies modified program downloaded installed executed users computers edit time source code program edited spans initial creation bug fix refactoring addition new features editing typically performed person automated design tools metaprogramming systems may also used compile time source code translated machine code compiler part involves language checking ensuring proper use type system result successful compilation executable link time connects necessary machine code components program including externals common programs use functions implemented external libraries must properly linked together two types linking static linking connection made compiler always prior execution dynamic linking however performed operating system os even execution distribution time process transferring copy program user distribution format typically executable may also source code especially program written interpreted language means distribution physical media usb flash drive remote download via internet installation time gets distributed program ready execution user computer often includes storing executable future loading os load time os takes program executable storage hard drive places active memory order begin execution run time execution phase central processing unit executes program machine code instructions programs may run indefinitely execution terminates either normal expected behavior abnormality crash
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Programming language topics
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bnc software bnc short bounced network connection piece software used relay traffic connections computer networks much like proxy using bnc allows user hide original source user connection providing privacy well ability route traffic specific location bnc also used hide true target user connects one common usage internet relay chat irc via bnc running remote servers environment easy ascertain user ip address bnc may help hide original connection source well providing opportunity vhosts virtual hosts use vhost conceal connection better merely adds statement hostname many bncs remain connected irc server event client disconnect internet often state changes tracked may relayed client upon reconnection implementations opt store messages sent across network client would normally received send upon clients reconnection often considered much resource dependent commercial hosting services provide logging features bot like functions may included various implementations standard list bouncer software bncs also often used file transfer protocol ftp hide user server route traffic specific location ftp bouncers divided two different categories entry traffic entry bouncer acts gateway server hide existence actual server entry bouncers like cubnc used multi-server setup easy access server load balancing removes need select ftp server log trying access server farm traffic bouncers relay traffic host installed used appears bouncer actually ftp server thus hiding real location server completely multiple traffic bouncers installed parallel order balance traffic load across different links elaborate bouncers even bounce secure ssl/tls connections
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Computer security
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apple a6 apple a6 32-bit package package pop system chip soc designed apple inc. introduced september 12 2012 launch iphone 5 apple states twice fast twice graphics power compared predecessor apple a5 software updates devices using chip ceased 2017 release ios 11 apple a6 said use 1.3 ghz custom apple-designed armv7-a architecture based dual-core cpu called swift rather licensed cpu arm like previous designs integrated 266 mhz triple-core powervr sgx543mp3 graphics processing unit gpu swift core a6 uses new tweaked instruction set featuring elements arm cortex-a15 support advanced simd v2 vfpv4 analysis suggests swift core triple-wide frontend two fpus compared two-wide core single fpu cortex-a9 based predecessor a6 processor package also incorporates 1 gb lpddr2-1066 ram compared 512mb lpddr2-800 ram apple a5 providing double memory capacity increasing theoretical memory bandwidth 6.4 gb/s 8.5 gb/s a6 includes upgraded image signal processor isp compared isp a5 improves speed image capture low-light performance noise reduction video stabilization a6 manufactured samsung high-κ metal gate hkmg 32 nm process chip 96.71 mm large 22 smaller a5 a6 also consumes less energy predecessor version a6 higher frequency four graphic cores called apple a6x found fourth generation ipad apple a6 chip used iphones ipads generation ipod touch ipad minis apple tvs
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Computer architecture
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compact pro compact pro software data compression utility archiving compressing files apple macintosh platform major competitor stuffit early 1990s producing smaller archives less time able create self-extracting archives without use external program well distributed via shareware greatly helped popularity pc version also available extractorpc neither program actively supported introduced early 1990s compact pro originally known compactor competed stuffit suffering neglect original developer moved projects compact pro sported clean interface variety new features quickly made favorite among digerati quickly drove stuffit leadership position became popular bbs systems stuffit 3.0 fought back even powerful compression algorithm shareware version called stuffit lite features freeware stuffit expander could decompress stuffit archives compact pro archives compact pro never really regained momentum release stuffit expander maintained niche among loyal users preparation tool cyclos smaller installer delivery package notably used ambrosia software disappeared market late 1990s compact pro also served inspiration zipit pkzip-compatible archiver expressly designed look work like compact pro like archiver systems compact pro primary purpose package compress files transmission extract side link unlike systems compact pro used non-modal mac-like ui widely lauded press notable features included ability extract everything archive double-clicking finder key held automatically recognizing converting binhex formatted files back native format without separate step compact pro also featured easy-to-use system splitting files parts fit floppy disks feature archivers implemented external program odd oft-used feature ability include images notes would display archive opened using basic mechanism teachtext compact pro also included ability produce self-extracting archives although becoming common archivers time particular implementation notable extractor stub code quite small 13 kb compared stuffit 38 kb era 14400 bit/s modems worthwhile savings many considered even large bother number small third-party utilities strip stub existing archive compact pro stub could also expand files split parts rare feature time time introduction compact pro offered far fastest best compression mac use compactor files never 1 larger stuffit deluxe better best guess modes anywhere 25 400 faster ironically compact pro even faster stuffit extracting stuffit files often least double performance also allowed background operation multifinder speed remained superior systems even major upgrades ended testing late 1990s show remaining significantly faster smaller versions stuffit years later normal archives created compact pro use .cpt file extension self-extracting versions used .sea file extensions normally needed mac commonly used archives would typically stored system would normally require pcs instance
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Computer file systems
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northbound interface computer networking computer architecture northbound interface component interface conceptualizes lower level details e.g. data functions used component northbound interface used interface higher level layers using southbound interface higher level component architectural overviews northbound interface normally drawn top component defined hence name northbound interface southbound interface decomposes concepts technical details mostly specific single component architecture southbound interfaces drawn bottom architectural overview northbound interfaces normally talk southbound interfaces higher level components vice versa northbound interface typically output-only interface opposed one accepts user input found carrier-grade network telecommunications network elements languages protocols commonly used include snmp tl1 example device capable sending syslog messages configurable user said implement northbound interface examples include smash ipmi wsman soap etc
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Computer architecture
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windows embedded ce 6.0 windows embedded ce 6.0 codenamed yamazaki sixth major release microsoft windows embedded operating system targeted enterprise specific tools industrial controllers consumer electronics devices like digital cameras ce 6.0 features kernel supports 32,768 processes 32 process limit prior versions process receives 2 gb virtual address space 32 mb windows embedded ce 6.0 released november 1 2006 includes partial source code os currently serves basis zune hd windows mobile 6.5 based windows ce 5.2 windows phone 7 first major release windows phone operating system based windows embedded ce 6.0 r3 although windows phone 7 also using windows embedded compact 7 features windows embedded ce 6.0 r3 finalized september 2009 oems serves base platform zune hd windows phone 7 ce 6.0 r3 includes following new features abilities note features listed specific windows phone 7 zune hd
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Computer architecture
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steel bank common lisp steel bank common lisp sbcl free common lisp implementation features high-performance native compiler unicode support threading name steel bank common lisp reference carnegie mellon university common lisp sbcl forked andrew carnegie made fortune steel industry andrew mellon successful banker sbcl descends cmucl descended spice lisp including early implementations mach operating system ibm rt pc three rivers computing corporation perq computer 1980s william newman originally announced sbcl variant cmucl december 1999 main point divergence time clean bootstrapping procedure cmucl requires already compiled executable binary compile cmucl source code whereas sbcl supported bootstrapping theoretically ansi-compliant common lisp implementation sbcl became sourceforge project september 2000 original rationale fork continue initial work done newman without destabilizing cmucl time already mature much-used implementation forking amicable since significant flows code cross-pollination two projects since sbcl attracted several developers ported multiple hardware architectures operating systems undergone many changes enhancements dropped support several cmucl extensions considers beyond scope project motif interface also developed many new ones including native threading unicode support version 1.0 released november 2006 active development continues william newman stepped project administrator sbcl april 2008 several developers taken interim management releases time tenth anniversary sbcl workshop organized
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Programming language topics
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inspec inspec major indexing database scientific technical literature published institution engineering technology iet formerly institution electrical engineers iee one iet forerunners inspec coverage extensive fields physics computing control engineering subject coverage includes astronomy electronics communications computers computing computer science control engineering electrical engineering information technology physics manufacturing production mechanical engineering due emerging concept technology business inspec also includes information technology business portfolio inspec indexed journals publishing high quality research integrating technology management economics social sciences domains sample journals include annual review financial economics aslib journal information management australian journal management international journal management economics social sciences inspec started 1967 outgrowth science abstracts service electronic records distributed magnetic tape 1980s available u.s. knowledge index low-priced dial-up version dialog service individual users made popular nearly 50 years iet employed scientists manually review items included inspec hand-indexing literature using expertise subject area make judgement call terms classification codes applied thanks work significant thesaurus developed enables content indexed far accurately context turn helps end-users discover relevant literature may otherwise remained hidden typical search queries making inspec essential tool prior art patentability searches patent drafting access inspec currently internet inspec direct various resellers inspec several print counterparts computer control abstracts frequency 12 per year covers computers computing information technology electrical electronics abstracts frequency 12 per year covers topics telecommunications electronics radio electrical power optoelectronics printed indexes subject author indexes subject guide produced twice per year physics abstracts frequency 24 per year abstracting indexing service first published institution electrical engineers first circulated science abstracts volume 1 volume 5 1898 1902 1903 1971 database different titles closely related names science abstracts section physics science abstracts section physics abstracts volume 6 volume 74 1972 societies associated authors service american institute physics 1975 1976 institute electrical electronics engineers also became author 1980 database also issued inspec-physics various formats also available part inspec database presently part inspec section physics database time physics abstracts title employed throughout 1990s science fiction writer arthur c. clarke b.s degree physics mathematics honors king college assistant editor physics abstracts 1949–1951 position allowed clarke access world ’ leading scientific journals first issue science abstracts published january 1898 first year total 1,423 abstracts published monthly intervals end year author subject index added first issue contained 110 abstracts divided 10 sections science abstracts result joint collaboration institution electrical engineers iee physical society london publication time provided without charge members societies cost publication mainly borne iee physical society financial contributions also received institution civil engineers royal society british association advancement science 1902 annual number abstracts published increased 2,362 may 1903 decided split publication two parts physics b electrical engineering decision allowed subject scope widen particularly physics result allowed larger quantity material covered since 1967 electronic access science abstracts provided inspec
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Databases
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supercomputer architecture approaches supercomputer architecture taken dramatic turns since earliest systems introduced 1960s early supercomputer architectures pioneered seymour cray relied compact innovative designs local parallelism achieve superior computational peak performance however time demand increased computational power ushered age massively parallel systems supercomputers 1970s used processors 1990s machines thousands processors began appear end 20th century massively parallel supercomputers tens thousands off-the-shelf processors norm supercomputers 21st century use 100,000 processors graphic units connected fast connections throughout decades management heat density remained key issue centralized supercomputers large amount heat generated system may also effects reducing lifetime system components diverse approaches heat management pumping fluorinert system hybrid liquid-air cooling system air cooling normal air conditioning temperatures systems massive number processors generally take one two paths one approach e.g. grid computing processing power large number computers distributed diverse administrative domains opportunistically used whenever computer available another approach large number processors used close proximity e.g. computer cluster centralized massively parallel system speed flexibility interconnect becomes important modern supercomputers used various approaches ranging enhanced infiniband systems three-dimensional torus interconnects since late 1960s growth power proliferation supercomputers dramatic underlying architectural directions systems taken significant turns early supercomputers relied small number closely connected processors accessed shared memory supercomputers 21st century use 100,000 processors connected fast networks throughout decades management heat density remained key issue centralized supercomputers seymour cray get heat motto central design philosophy continued key issue supercomputer architectures e.g. large-scale experiments blue waters large amount heat generated system may also effects reducing lifetime system components diverse approaches heat management e.g cray 2 pumped fluorinert system system x used hybrid liquid-air cooling system blue gene/p air-cooled normal air conditioning temperatures heat aquasar supercomputer used warm university campus heat density generated supercomputer direct dependence processor type used system powerful processors typically generating heat given similar underlying semiconductor technologies early supercomputers used fast closely packed processors took advantage local parallelism e.g. pipelining vector processing time number processors grew computing nodes could placed away e.g. computer cluster could geographically dispersed grid computing number processors supercomputer grows component failure rate begins become serious issue supercomputer uses thousands nodes may fail per year average system experience several node failures day price/performance general purpose graphic processors gpgpus improved number petaflop supercomputers tianhe-i nebulae started rely however systems k computer continue use conventional processors sparc-based designs overall applicability gpgpus general purpose high performance computing applications subject debate gpgpu may tuned score well specific benchmarks overall applicability everyday algorithms may limited unless significant effort spent tune application towards however gpus gaining ground 2012 jaguar supercomputer transformed titan replacing cpus gpus number independent processors supercomputer increases way access data file system share access secondary storage resources becomes prominent years number systems distributed file management developed e.g ibm general parallel file system beegfs parallel virtual file system hadoop etc number supercomputers top100 list tianhe-i use linux lustre file system cdc 6600 series computers early attempts supercomputing gained advantage existing systems relegating work peripheral devices freeing cpu central processing unit process actual data minnesota fortran compiler 6600 could sustain 500 kiloflops standard mathematical operations early supercomputers cray 1 cray 2 appeared afterwards used small number fast processors worked harmony uniformly connected largest amount shared memory could managed time early architectures introduced parallel processing processor level innovations vector processing processor perform several operations one clock cycle rather wait successive cycles time number processors increased different architectural issues emerged two issues need addressed number processors increases distribution memory processing distributed memory approach processor physically packaged close local memory memory associated processors away based bandwidth latency parameters non-uniform memory access 1960s pipelining viewed innovation 1970s use vector processors well established 1980s many supercomputers used parallel vector processors relatively small number processors early systems allowed easily use shared memory architecture allows processors access common pool memory early days common approach use uniform memory access uma access time memory location similar processors use non-uniform memory access numa allowed processor access local memory faster memory locations cache-only memory architectures coma allowed local memory processor used cache thus requiring coordination memory values changed number processors increases efficient interprocessor communication synchronization supercomputer becomes challenge number approaches may used achieve goal instance early 1980s cray x-mp system shared registers used approach processors access shared registers move data back forth used interprocessor communication synchronization however inherent challenges managing large amount shared memory among many processors resulted move distributed architectures 1980s demand computing power increased trend much larger number processors began ushering age massively parallel systems distributed memory distributed file systems given shared memory architectures could scale large number processors hybrid approaches distributed shared memory also appeared early systems computer clustering approach connects number readily available computing nodes e.g personal computers used servers via fast private local area network activities computing nodes orchestrated clustering middleware software layer sits atop nodes allows users treat cluster large one cohesive computing unit e.g via single system image concept computer clustering relies centralized management approach makes nodes available orchestrated shared servers distinct approaches peer peer grid computing also use many nodes far distributed nature 21st century top500 organization semiannual list 500 fastest supercomputers often includes many clusters e.g world fastest 2011 k computer distributed memory cluster architecture large number local semi-independent computing nodes used e.g cluster architecture speed flexibility interconnect becomes important modern supercomputers taken different approaches address issue e.g tianhe-1 uses proprietary high-speed network based infiniband qdr enhanced feiteng-1000 cpus hand blue gene/l system uses three-dimensional torus interconnect auxiliary networks global communications approach node connected six nearest neighbors similar torus used cray t3e massive centralized systems times use special-purpose processors designed specific application may use field-programmable gate arrays fpga chips gain performance sacrificing generality examples special-purpose supercomputers include belle deep blue hydra playing chess gravity pipe astrophysics mdgrape-3 protein structure computation molecular dynamics deep crack breaking des cipher grid computing uses large number computers distributed diverse administrative domains opportunistic approach uses resources whenever available example boinc volunteer-based opportunistic grid system boinc applications reached multi-petaflop levels using close half million computers connected internet whenever volunteer resources become available however types results often appear top500 ratings run general purpose linpack benchmark although grid computing success parallel task execution demanding supercomputer applications weather simulations computational fluid dynamics remained reach partly due barriers reliable sub-assignment large number tasks well reliable availability resources given time quasi-opportunistic supercomputing large number geographically disperse computers orchestrated built-in safeguards quasi-opportunistic approach goes beyond volunteer computing highly distributed systems boinc general grid computing system globus allowing middleware provide almost seamless access many computing clusters existing programs languages fortran c distributed among multiple computing resources quasi-opportunistic supercomputing aims provide higher quality service opportunistic resource sharing quasi-opportunistic approach enables execution demanding applications within computer grids establishing grid-wise resource allocation agreements fault tolerant message passing abstractly shield failures underlying resources thus maintaining opportunism allowing higher level control air-cooled ibm blue gene supercomputer architecture trades processor speed low power consumption larger number processors used room temperature using normal air-conditioning second-generation blue gene/p system processors integrated node-to-node communication logic energy-efficient achieving 371 mflops/w k computer water-cooled homogeneous processor distributed memory system cluster architecture uses 80,000 sparc64 viiifx processors eight cores total 700,000 cores—almost twice many system comprises 800 cabinets 96 computing nodes 16 gb memory 6 i/o nodes although powerful next five systems top500 list combined 824.56 mflops/w lowest power performance ratio current major supercomputer system follow system k computer called primehpc fx10 uses six-dimensional torus interconnect still one processor per node unlike k computer tianhe-1a system uses hybrid architecture integrates cpus gpus uses 14,000 xeon general-purpose processors 7,000 nvidia tesla general-purpose graphics processing units gpgpus 3,500 blades 112 computer cabinets 262 terabytes distributed memory 2 petabytes disk storage implemented via lustre clustered files tianhe-1 uses proprietary high-speed communication network connect processors proprietary interconnect network based infiniband qdr enhanced chinese made feiteng-1000 cpus case interconnect system twice fast infiniband slower interconnects supercomputers limits specific approaches continue tested boundaries reached large scale experiments e.g. 2011 ibm ended participation blue waters petaflops project university illinois blue waters architecture based ibm power7 processor intended 200,000 cores petabyte globally addressable memory 10 petabytes disk space goal sustained petaflop led design choices optimized single-core performance hence lower number cores lower number cores expected help performance programs scale well large number processors large globally addressable memory architecture aimed solve memory address problems efficient manner type programs blue waters expected run sustained speeds least one petaflop relied specific water-cooling approach manage heat first four years operation national science foundation spent 200 million project ibm released power 775 computing node derived project technology soon thereafter effectively abandoned blue waters approach architectural experiments continuing number directions e.g cyclops64 system uses supercomputer chip approach direction away use massive distributed processors 64-bit cyclops64 chip contains 80 processors entire system uses globally addressable memory architecture processors connected non-internally blocking crossbar switch communicate via global interleaved memory data cache architecture half sram bank used scratchpad memory although type architecture allows unstructured parallelism dynamically non-contiguous memory system also produces challenges efficient mapping parallel algorithms many-core system
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Distributed computing architecture
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list file systems following lists identify characterize link thorough information computer file systems many older operating systems support one native file system bear name apart name operating system disk file systems usually block-oriented files block-oriented file system sequences blocks often featuring fully random-access read write modify operations file systems built-in checksumming either mirroring parity extra redundancy one several block devices solid state media flash memory similar disks interfaces different problems low level require special handling wear leveling different error detection correction algorithms typically device solid-state drive handles operations internally therefore regular file system used however certain specialized installations embedded systems industrial applications file system optimized plain flash memory advantageous record-oriented file systems files stored collection records typically associated mainframe minicomputer operating systems programs read write whole records rather bytes arbitrary byte ranges seek record boundary within records sophisticated record-oriented file systems common simple databases file systems shared-disk file systems also called shared-storage file systems san file system clustered file system even cluster file systems primarily used storage area network nodes directly access block storage file system located makes possible nodes fail without affecting access file system nodes shared-disk file systems normally used high-availability cluster together storage hardware raid shared-disk file systems normally scale 64 128 nodes shared-disk file systems may symmetric metadata distributed among nodes asymmetric centralized metadata servers distributed file systems also called network file systems many implementations made location dependent access control lists acls unless otherwise stated distributed fault-tolerant replication data nodes servers servers/clients high availability offline disconnected operation distributed parallel file systems stripe data multiple servers high performance normally used high-performance computing hpc distributed parallel file systems use object storage device osd lustre called ost chunks data together centralized metadata servers distributed file systems also parallel fault tolerant stripe replicate data multiple servers high performance maintain data integrity even server fails data lost file systems used high-performance computing hpc high-availability clusters file systems listed focus high availability scalability high performance unless otherwise stated development may called cooperative storage cloud really file systems allow access file systems operating system standpoint
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Computer file systems
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sun-ni law sun-ni law sun ni law also known memory-bounded speedup memory-bounded speedup model states computing power increases corresponding increase problem size constrained system ’ memory capacity general system grows computational power problems run system increase size analogous amdahl law says problem size remains constant system sizes grow gustafson law proposes problem size scale bound fixed amount time sun-ni law states problem size scale bound memory capacity system sun-ni law initially proposed xian-he sun lionel ni proceedings ieee supercomputing conference 1990 increasing disparity cpu speed memory data access latency application execution time often depends memory speed system predicted sun ni data access become premier performance bottleneck high-end computing fact one see intuition behind sun-ni law system resources increase applications often bottlenecked memory speed bandwidth thus application achieve larger speedup utilizing memory capacity system sun-ni law applied different layers memory hierarchy system l1 cache main memory memory-bounded function w=g reveals trade-off computing memory algorithm system architecture design three speedup models sun-ni gustafson amdahl provide metric analyze speedup parallel computing amdahl ’ law focuses time reduction given fixed-size problem amdahl ’ law states sequential portion problem algorithm limits total speedup achieved system resources increase gustafson ’ law suggests beneficial build large-scale parallel system speedup grow linearly system size problem size scaled maintain fixed execution time yet memory access latency often becomes dominant factor application ’ execution time applications may scale meet time bound constraint sun-ni law instead constraining problem size time constrains problem memory capacity system words bounds based memory sun-ni law generalization amdahl law gustafson law memory-bounded function g =1 resolves amdahl law memory-bounded function g =m number processors resolves gustafson law let formula_1 scaled workload memory space constraint memory bounded speedup defined suppose formula_2 portion workload parallelized formula_3 sequential portion workload let formula_4 function reflects parallel workload increase factor memory capacity increases times let formula_5 formula_6 formula_7 memory capacity one node thus formula_8 memory bounded speedup formula_9 power function formula_10 rational numbers b formula_11 formula_12 power function coefficient 1 thus taking highest degree term determine complexity algorithm rewrite memory bounded speedup formula_13 equation formula_14 represents influence memory change change problem size suppose formula_15 memory-bounded speedup model reduces amdahl law since problem size fixed independent resource increase suppose formula_16 memory-bounded speedup model reduces gustafson law means memory capacity increases times workload also increases times data needed local every node system often simplicity matching notation amdahl law gustafson law letter g used represent memory bound function formula_14 n replaces using notation get formula_18 suppose one would like determine memory-bounded speedup matrix multiplication memory requirement matrix multiplication roughly formula_19 n dimension two n x n source matrices computation requirement formula_20 thus formula_21 formula_22 thus memory-bounded speedup matrix multiplication formula_23 following another matrix multiplication example illustrates rapid increase parallel execution time execution time n x n matrix uniprocessor formula_24 memory usage formula_25 suppose 10000 -by- 10000 matrix takes 800 mb memory factorized 1 hour uniprocessor scaled workload suppose possible factorize 320,000 -by- 320,000 matrix 32 hours time increase quite large increase problem size may valuable someones whose premier goal accuracy example astrophysicist may interested simulating n-body problem number particles large possible example shows computation intensive applications memory capacity need proportionally scale computing power memory-bounded speedup model first work reveal memory performance constraint high-end computing presents quantitative mathematical formulation trade-off memory computing based memory-bounded function w=g n w work thus also computation applications memory requirement terms capacity g reuse rate w=g gives simple effective description relation computation memory requirement architecture viewpoint memory-bounded model suggests size well speed cache match cpu performance today modern microprocessors pentium pro alpha 21164 strong arm sa110 longson-3a use 80 transistors on-chip cache rather computing components algorithm design viewpoint reduce number memory accesses reuse data possible function g gives reuse rate today term memory bound functions become general term refers functions involve extensive memory access memory complexity analysis become discipline computer algorithm analysis
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Computer architecture
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unionfs unionfs filesystem service linux freebsd netbsd implements union mount file systems allows files directories separate file systems known branches transparently overlaid forming single coherent file system contents directories path within merged branches seen together single merged directory filesystem mounting branches priority one branch specified branches contain file name different branches may either read-only read-write file systems writes virtual merged copy directed specific real file system allows file system appear writable without actually allowing writes change file system also known copy-on-write may desirable media physically read-only case live cds unionfs originally developed professor erez zadok team stony brook university knoppix union file system cd-rom dvd file system contained image file called knoppix.img knoppix-data.img knoppix 7 writable drive usb memory stick made writable drive priority read-only filesystem allows user change files system new file stored image transparently used instead one cd unionfs also used create single common template number file systems security reasons sometimes used ad hoc snapshotting system docker uses unionfs layer docker images actions done base image layers created documented layer fully describes recreate action strategy enables docker lightweight images layer updates need propagated compared full vms example ubuntultsp linux terminal server project implementation ubuntu uses unionfs pxe booting thin thick clients unionfs linux two versions version 1.x standalone one built module version 2.x newer redesigned reimplemented one aufs alternative version unionfs overlayfs written miklos szeredi used openwrt considered ubuntu merged mainline linux kernel 26 october 2014 many years development discussion version 3.18 kernel unionfs-fuse independent project implemented user space filesystem program instead kernel module patch like unionfs supports copy-on-write read-only read-write branches plan 9 bell labs operating system uses union mounts extensively build custom namespaces per user processes union mounts also available bsd since least 1995 gnu hurd implementation unionfs january 2008 works results read-only mount-point mhddfs works like unionfs permits balancing files drives free space available implemented user space filesystem mergerfs fuse based union filesystem offers multiple policies accessing writing files well advanced features xattrs managing mixed ro rw drives link cow etc. sun microsystems introduced first implementation stacked layered file system copy-on-write whiteouts hiding files lower layers higher layers etc translucent file service sunos 3 circa 1986 jailbreakme 3.0 tool jailbreaking ios devices released july 2011 uses unionfs techniques speed installation process operating system modification
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Computer file systems
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sheerpower4gl sheerpower 4gl fourth-generation programming language developed touch technologies inc sheerpower 4gl result porting touch technologies intouch 4gl programming language runs openvms dec alpha vax computers windows launching 2000 downloads free official sheerpower 4gl website sheerpower 4gl similar basic programming language easy learn sheerpower 4gl several key features 1 free hobbyists non-profit organizations 2 extremely fast able compile millions lines per minute modern systems 3 web scripting features make fast easy develop dynamic web pages using sheerpower basic-like syntax version 5.0 official release containing syntax logic web scripting sheerpower 4 sheerpower utilizes perfect precision math package patent 7149765 apparatus method precision binary numbers numerical operations applied precision math eliminates rounding errors experienced using floating point data type 5 sheerpower comes bundled ars advanced record system database engine ars proprietary database engine also developed touch technologies inc. tti created ars engine performance critical many applications example ars 20 times faster mysql shared read/write operations 6 open database connectivity sheerpower supports database engines odbc interface ars engine accessed via odbc database applications 7 sheerpower internet services spins webserver also comes bundled sheerpower 4gl spins webserver comes bundled sheerpower developed simplicity use high-speed performance modern multi-core system spins web server perform 1,000 page hits per second—given enough bandwidth course 8 also common gateway interface cgi interface built sheerpower along many built-in functions designed high-performance increased programmer productivity sheerpower 4gl following built-in security features 1 run sheerpower program windows temporary folder stops computer viruses written sheerpower programs emailed run email opened 2 sheerpower mix data code database operation makes impervious sql injection attacks binary distribution available microsoft windows nt 2000 2003 xp vista virtual machine downloaded alone purpose running .spsrc .sprun programs sheerpower source code files deployed files code encrypted software free non-commercial use terms undefined besides levels support business customers non-profit organizations hobbyist programmers use free license comes download license fees outlined wanting develop applications commercial business use high-priority support packages available email web forum support available charge
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Programming language topics
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multi-user software multi-user software software allows access multiple users computer time-sharing systems multi-user systems batch processing systems mainframe computers may also considered multi-user avoid leaving cpu idle waits i/o operations complete however term multitasking common context example unix server multiple remote users access via serial port secure shell unix shell prompt time another example uses multiple x window sessions spread across multiple terminals powered single machine example use thin client similar functions also available mp/m concurrent dos multiuser dos flexos multi-user operating systems windows versions windows nt family support simultaneous access multiple users example via remote desktop connection well ability user disconnect local session leaving processes running work behalf another user logs uses system operating system provides isolation user processes users enabling execute concurrently management systems implicitly designed used multiple users typically one system administrator end-user community complementary term single-user commonly used talking operating system usable one person time reference single-user software license agreement multi-user operating systems unix sometimes single user mode runlevel available emergency maintenance
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Operating systems
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mindtouch mindtouch american multinational technology company headquartered san diego california designs develops sells saas computer software online services company software products include mindtouch formerly called mindtouch responsive mindtouch 4 mindtouch tcs mindtouch core mindtouch allows team create publish edit content structure content within responsive user interface online services include touchpoints crm integrations success program custom software development team helps branding information architecture custom integrations new existing customers mindtouch founded aaron fulkerson steve bjorg 2005 january 2016 mindtouch announced series venture capital funding round totaling 12 million usd peakspan capital led round participation sk ventures sap se mindtouch started mediawiki 2005 first release name dekiwiki occurred july 2006 featuring xhtml place wikitext wysiwyg editor lucene-based search main functionality mindtouch wiki access php frontend provided wiki along wysiwyg editor multi-language support named polyglot allows switching interface content languages per page per section per user basis multilingual wikis engine prioritizes search results user ’ default language mindtouch cites 8.05 release deki first polyglot application web mindtouch core allowed user access edit pages stored xml rather wikitext mindtouch core open-source enterprise web-based wiki software mashup platform pages edited using gui editor could manipulated xml web service software supported authentication apache iis modules permissions could applied individual pages page hierarchies open source version mindtouch core distributed sourceforge terms gnu general public license parts gnu lesser general public license apache license dekiscript lightweight interpreted programming language allows users add dynamic content mindtouch pages mindtouch core allowed embedded directly web pages extended xml extensions mindtouch core used multiple connectors perform mashups mindtouch core shipped extensions allowing connection numerous online services including systems google maps windows live flickr yahoo unsupported commercial license enabled features connectors sugarcrm salesforce linkedin mysql microsoft sql server microsoft access april 9 2013 mindtouch inc. announced would longer support open source offering mindtouch core last open-source releases mindtouch core still available sourceforge mindtouch 4 developed open-source mindtouch core source code base mindtouch current version software service second iteration mindtouch 4 mindtouch allows team create publish edit content structure content within responsive user interface integration partnerships crm vendors sap salesforce.com provide support agents ability use mindtouch content customer support workflows amazon ’ aws also partnered mindtouch january 2016 mindtouch announced series venture capital funding round totaling 12 million usd peakspan capital led round participation sk ventures sap se mindtouch cloud infrastructure delivers weekly update bug fixes feature changes mindtouch forked mediawiki 2005 first release name dekiwiki occurred july 2006 featuring xhtml place wikitext wysiwyg editor lucene-based search consequently backend completely reimplemented c resulting api built web services top new dream distributed rest application manager server toolset mindtouch responsive latest version mindtouch saas offering replacing mindtouch 4 mindtouch 4 forked internally within mindtouch inc. open-source mindtouch core source code base early 2010 addition legacy php c components mindtouch core mindtouch responsive software infrastructure includes technologies nodejs elasticsearch f amazon sqs amazon lambda amazon redshift redis haproxy puppet
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Distributed computing architecture
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nuget nuget free open-source package manager designed microsoft development platform formerly known nupack since introduction 2010 nuget evolved larger ecosystem tools services nuget distributed visual studio extension starting visual studio 2012 nuget comes pre-installed default nuget also integrated sharpdevelop nuget also used command line automated scripts supports multiple programming languages including chocolatey machine-level package manager installer software packages built windows nt platform execution engine using nuget packaging infrastructure windows powershell provide automation tool installing software windows machines designed simplify process user perspective name extension pun nuget nougat everyone loves chocolatey nougat chocolatey invoked packagemanagement module formerly 'oneget powershell version 5.0
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Operating systems
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ifilter ifilter plugin allows microsoft search engines index various file formats documents email attachments database records audio metadata etc become searchable without appropriate ifilter contents file parsed indexed search engine obtained standalone packages bundled certain software adobe reader libreoffice microsoft office openoffice also refers software interface needed implement plugins ifilter acts plug-in extracting full-text metadata search engines search engine usually works two steps step 1 search engine n't understand format document therefore looks windows registry appropriate ifilter extract data document format filtering embedded formatting non-textual data windows indexing service newer windows search windows desktop search msn desktop search internet information server sharepoint portal server windows sharepoint services wss site server exchange server sql server products based microsoft search technology support indexing technology also ifilters used sql server component sql server full text search service
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Operating systems
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cryptek cryptek company develops sells information security products services governments corporations cryptek headquartered dulles virginia united states cryptek founded 1986 cryptek secure communications inc. time company designed manufactured field-deployable secure fax machines military united states 1988 cryptek acquired general kinetics manufacturer secure enclosures products 1993 general kinetics also acquired verdix manufacturer secure computer networking equipment government united states 1996 private equity firm angelo gordon co. acquired fax secure networking businesses general kinetics company continued operate cryptek secure communications llc company simplified name cryptek inc. 2002 2005 cryptek went corporate restructuring bill anderson became president ceo 2007 cryptek acquired three companies secure systems group sterling virginia united states emcon emanation control ltd ottawa ontario canada secure systems technologies ltd sst gloucester united kingdom year cryptek also acquired assets ion networks south plainfield new jersey united states november 2008 company filed chapter 11 bankruptcy protection march 2009 cryptek petitioned move chapter 7 bankruptcy senior management purchase assets new company cryptek technologies inc. began operation march 11 2009 july 2009 cryptek acquired defense aerospace company api technologies corp
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Computer security
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aolserver aolserver aol open source web server aolserver multithreaded tcl-enabled used large scale dynamic web sites aolserver distributed mozilla public license aolserver originally developed navisoft name naviserver changed names aol bought company 1995 philip greenspun convinced america online open-source program 1999 aolserver first http server program combine multithreading built-in scripting language pooling persistent database connections database-backed web sites enabled performance improvements 100× compared standard practices time cgi scripts opened fresh database connections every page load eventually http server programs able achieve similar performance similar architecture aolserver key component open architecture community system openacs advanced open-source toolkit developing web applications sept 2007 port aolserver iphone made available later forked name joggame server fork described sourceforge project page spin-off aolserver devices naviserver also hosted sourceforge fork aolserver
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Web technology
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melissa hathaway melissa hathaway born november 10 1968 leading expert cyberspace policy cybersecurity served two u.s. presidential administrations 2007 2009 including 8 months white house spearheading cyberspace policy review president barack obama leading comprehensive national cybersecurity initiative cnci president george w. bush president hathaway global strategies llc senior fellow member board regents potomac institute policy studies distinguished fellow centre international governance innovation canada non-resident research fellow kosciuszko institute poland previously senior adviser harvard kennedy school ’ belfer center hathaway received b.a american university graduated us armed forces staff college special certificate information operations hathaway employed consulting firm evidence based research work included developing models detection cocaine movement united states june 1993 february 2007 hathaway worked consulting firm booz allen hamilton focusing information operations long-range strategy policy support business units work included evaluations new force options across electromagnetic spectrum design development novel techniques mapping social business process infrastructure relationships hathaway served senior advisor director national intelligence mike mcconnell cyber coordination executive chaired national cyber study group ncsg role ncsg contributed development comprehensive national cybersecurity initiative cnci hathaway appointed director joint interagency cyber task force january 2008 hathaway named acting senior director cyberspace national security homeland security councils february 9 2009 placed charge 60-day inter-agency review plan programs activities underway throughout government dedicated cyber security january 2009 request assistant president national security affairs ms. hathaway asked lead 60-day cyberspace policy review president obama assembled team experienced government cyber experts identified 250 recommendations may 2009 president obama presented blueprint cyberspace policy review announced cybersecurity would one administration priorities recognized ms. hathaway leadership noted president said “ opportunities everyone—academia industry governments—to work together build trusted resilient communications information infrastructure. ” august 3 2009 announced hathaway would return private sector resignation taking effect august 21 2009 departing cited frustration yet selected new position cyber coordinator n't willing continue wait longer 'm empowered right continue drive change october 1 2009 till project conclusion 2015 hathaway served senior adviser project minerva harvard kennedy school also one lead instructors executive program cybersecurity intersection policy technology hathaway president hathaway global strategies consulting firm also serves advisor companies including cisco one thirty commissioners global commission internet governance
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Computer security
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ultracopier ultracopier file-copying software windows macos linux supersedes supercopier main features include normal vs ultimate version difference supercopier ultracopier skin supercopier skin ultracopier css use little bit cpu talk supercopier implies refer v3 less talk ultracopier implies refer supercopier v4 later rename ultracopier v1.4
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Computer file systems
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transaction-safe fat file system transaction-safe fat file system tfat transaction-safe extended fat file system texfat refer two file systems used microsoft products provide transaction-safety data stored disk goal reduce risk data loss cases power loss unexpected removal drive latter problem become common spread usb drives transaction-safe fat file system tfat tfat12 tfat16 tfat32 file systems driver layer modification original fat file systems fat12 fat16 fat32 maintaining two copies fat 0 fat 1 file allocation table instead two identical ones performing drive operation changes would made fat 1 operation complete fat 1 table would copied fat 0 updating stable view file system transaction-safe extended fat file system texfat texfat provides similar functionality tfat using exfat file system base file system instead fat introduced windows embedded ce 6.0 sometimes referred tfat well lead confusion original tfat described use exfat underlying file system allows larger files larger partitions texfat requires hardware-specific driver designed type media texfat volume resides due lack support desktop operating systems neither tfat texfat recommended removable media desktop os could still read drive could use transaction-safe features unexpected removal power outage could lead data loss addition directories created desktop os may transaction-safe even drive later attached tfat/texfat aware operating system
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Computer file systems
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smurf amplifier registry smurf amplifier registry blacklist networks internet misconfigured way used smurf amplifiers smurf denial service attacks probe networks vulnerability smurf amplification either add database remove database depending result test
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Computer security
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denial-of-service attack computing denial-of-service attack dos attack cyber-attack perpetrator seeks make machine network resource unavailable intended users temporarily indefinitely disrupting services host connected internet denial service typically accomplished flooding targeted machine resource superfluous requests attempt overload systems prevent legitimate requests fulfilled distributed denial-of-service attack ddos attack incoming traffic flooding victim originates many different sources effectively makes impossible stop attack simply blocking single source dos ddos attack analogous group people crowding entry door shop making hard legitimate customers enter thus disrupting trade criminal perpetrators dos attacks often target sites services hosted high-profile web servers banks credit card payment gateways revenge blackmail activism motivate attacks court testimony shows first demonstration dos attack made khan c. smith 1997 def con event disrupting internet access las vegas strip hour release sample code event led online attack sprint earthlink e-trade major corporations year follow march 5 2018 unnamed customer us-based service provider arbor networks fell victim largest ddos history reaching peak 1.7 terabits per second previous record set days earlier march 1 2018 github hit attack 1.35 terabits per second hong kong anti-extradition protests june 2019 messaging app telegram subject ddos attack aimed preventing protesters using coordinate movements founders telegram stated attack appears state sized actor via ip addresses originating china denial-of-service attacks characterized explicit attempt attackers prevent legitimate use service two general forms dos attacks crash services flood services serious attacks distributed distributed denial-of-service ddos large-scale dos attack perpetrator uses one unique ip address often thousands hosts infected malware distributed denial service attack typically involves around 3–5 nodes different networks fewer nodes may qualify dos attack ddos attack since incoming traffic flooding victim originates different sources may impossible stop attack simply using ingress filtering also makes difficult distinguish legitimate user traffic attack traffic spread across multiple points origin alternative augmentation ddos attacks may involve forging ip sender addresses ip address spoofing complicating identifying defeating attack scale ddos attacks continued rise recent years 2016 exceeding terabit per second common examples ddos attacks fraggle smurf syn flooding application layer ddos attack sometimes referred layer 7 ddos attack form ddos attack attackers target application-layer processes attack over-exercises specific functions features website intention disable functions features application-layer attack different entire network attack often used financial institutions distract security personnel security breaches 2013 application-layer ddos attacks represented 20 ddos attacks according research akamai technologies 51 percent application layer attacks q4 2013 q4 2014 16 percent q3 2014 q4 2014 november 2017 junade ali computer scientist cloudflare noted whilst network-level attacks continue high capacity occurring less frequently ali notes although network-level attacks becoming less frequent data cloudflare demonstrates application-layer attacks still showing sign slowing osi model iso/iec 7498-1 conceptual model characterizes standardizes internal functions communication system partitioning abstraction layers model product open systems interconnection project international organization standardization iso model groups similar communication functions one seven logical layers layer serves layer served layer example layer provides error-free communications across network provides communications path needed applications calls next lower layer send receive packets traverse path osi model definition application layer narrower scope often implemented osi model defines application layer user interface osi application layer responsible displaying data images user human-recognizable format interface presentation layer implementation application presentation layers frequently combined application layer ddos attack done mainly specific targeted purposes including disrupting transactions access databases requires fewer resources network layer attacks often accompanies attack may disguised look like legitimate traffic except targets specific application packets functions attack application layer disrupt services retrieval information search functions website advanced persistent dos apdos associated advanced persistent threat requires specialised ddos mitigation attacks persist weeks longest continuous period noted far lasted 38 days attack involved approximately 50+ petabits 50,000+ terabits malicious traffic attackers scenario may tactically switch several targets create diversion evade defensive ddos countermeasures eventually concentrating main thrust attack onto single victim scenario attackers continuous access several powerful network resources capable sustaining prolonged campaign generating enormous levels un-amplified ddos traffic apdos attacks characterised vendors provide so-called booter stresser services simple web-based front ends accept payment web marketed promoted stress-testing tools used perform unauthorized denial-of-service attacks allow technically unsophisticated attackers access sophisticated attack tools without need attacker understand use usually powered botnet traffic produced consumer stresser range anywhere 5-50 gbit/s cases deny average home user internet access united states computer emergency readiness team us-cert identified symptoms denial-of-service attack include additional symptoms may include attack conducted sufficiently large scale entire geographical regions internet connectivity compromised without attacker knowledge intent incorrectly configured flimsy network infrastructure equipment wide array programs used launch dos-attacks cases mydoom slowloris tools embedded malware launch attacks without knowledge system owner stacheldraht classic example ddos tool uses layered structure attacker uses client program connect handlers compromised systems issue commands zombie agents turn facilitate ddos attack agents compromised via handlers attacker using automated routines exploit vulnerabilities programs accept remote connections running targeted remote hosts handler control thousand agents cases machine may become part ddos attack owner consent example operation payback organized group anonymous loic typically used way along hoic wide variety ddos tools available today including paid free versions different features available underground market hacker related forums irc channels various dos-causing exploits buffer overflow cause server-running software get confused fill disk space consume available memory cpu time kinds dos rely primarily brute force flooding target overwhelming flux packets oversaturating connection bandwidth depleting target system resources bandwidth-saturating floods rely attacker higher bandwidth available victim common way achieving today via distributed denial-of-service employing botnet another target ddos attacks may produce added costs application operator latter uses resources based cloud computing case normally application used resources tied needed quality service level e.g responses less 200 ms rule usually linked automated software e.g amazon cloudwatch raise virtual resources provider order meet defined qos levels increased requests.the main incentive behind attacks may drive application owner raise elasticity levels order handle increased application traffic order cause financial losses force become less competitive floods may use specific packet types connection requests saturate finite resources example occupying maximum number open connections filling victim disk space logs banana attack another particular type dos involves redirecting outgoing messages client back onto client preventing outside access well flooding client sent packets land attack type attacker shell-level access victim computer may slow unusable crash using fork bomb kind application-level dos attack xdos xml dos controlled modern web application firewalls wafs pulsing zombies compromised computers directed launch intermittent short-lived floodings victim websites intent merely slowing rather crashing type attack referred degradation-of-service rather denial-of-service difficult detect regular zombie invasions disrupt hamper connection websites prolonged periods time potentially causing disruption concentrated floods exposure degradation-of-service attacks complicated matter discerning whether server really attacked normal traffic loads goal dos l2 possibly ddos attack cause launching defense mechanism blocks network segment attack originated case distributed attack ip header modification depends kind security behavior fully block attacked network internet without system crash distributed denial-of-service ddos attack occurs multiple systems flood bandwidth resources targeted system usually one web servers attack often result multiple compromised systems example botnet flooding targeted system traffic botnet network zombie computers programmed receive commands without owners knowledge server overloaded connections new connections longer accepted major advantages attacker using distributed denial-of-service attack multiple machines generate attack traffic one machine multiple attack machines harder turn one attack machine behavior attack machine stealthier making harder track shut attacker advantages cause challenges defense mechanisms example merely purchasing incoming bandwidth current volume attack might help attacker might able simply add attack machines end completely crashing website periods time malware carry ddos attack mechanisms one better-known examples mydoom dos mechanism triggered specific date time type ddos involved hardcoding target ip address prior release malware interaction necessary launch attack system may also compromised trojan allowing attacker download zombie agent trojan may contain one attackers also break systems using automated tools exploit flaws programs listen connections remote hosts scenario primarily concerns systems acting servers web stacheldraht classic example ddos tool uses layered structure attacker uses client program connect handlers compromised systems issue commands zombie agents turn facilitate ddos attack agents compromised via handlers attacker using automated routines exploit vulnerabilities programs accept remote connections running targeted remote hosts handler control thousand agents cases machine may become part ddos attack owner consent example operation payback organized group anonymous attacks use different types internet packets tcp udp icmp etc collections systems compromisers known botnets rootservers ddos tools like stacheldraht still use classic dos attack methods centered ip spoofing amplification like smurf attacks fraggle attacks also known bandwidth consumption attacks syn floods also known resource starvation attacks may also used newer tools use dns servers dos purposes unlike mydoom ddos mechanism botnets turned ip address script kiddies use deny availability well known websites legitimate users sophisticated attackers use ddos tools purposes extortioneven business rivals simple attacks syn floods may appear wide range source ip addresses giving appearance well distributed dos flood attacks require completion tcp three way handshake attempt exhaust destination syn queue server bandwidth source ip addresses trivially spoofed attack could come limited set sources may even originate single host stack enhancements syn cookies may effective mitigation syn queue flooding however complete bandwidth exhaustion may require involvement attacker mounts attack single host would classified dos attack fact attack availability would classed denial-of-service attack hand attacker uses many systems simultaneously launch attacks remote host would classified ddos attack reported new attacks internet things iot devices involved denial service attacks one noted attack made peaked around 20,000 requests per second came around 900 cctv cameras uk gchq tools built ddos named predators face rolling thunder 2015 ddos botnets dd4bc grew prominence taking aim financial institutions cyber-extortionists typically begin low-level attack warning larger attack carried ransom paid bitcoin security experts recommend targeted websites pay ransom attackers tend get extended extortion scheme recognize target ready pay first discovered 2009 http post attack sends complete legitimate http post header includes 'content-length field specify size message body follow however attacker proceeds send actual message body extremely slow rate e.g 1 byte/110 seconds due entire message correct complete target server attempt obey 'content-length field header wait entire body message transmitted take long time attacker establishes hundreds even thousands connections resources incoming connections server victim used hence making including legitimate connections impossible data sent notable unlike many dos attacks try subdue server overloading network cpu http post attack targets logical resources victim means victim would still enough network bandwidth processing power operate combined fact apache default accept requests 2gb size attack particularly powerful http post attacks difficult differentiate legitimate connections therefore able bypass protection systems owasp open source web application security project released testing tool test security servers type attacks challenge collapsar cc attack attack standard http requests sent targeted web server frequently uniform resource identifiers uris require complicated time-consuming algorithms database operations order exhaust resources targeted web server 2004 chinese hacker nicknamed kiki invented hacking tool send kinds requests attack nsfocus firewall named collapsar thus hacking tool known challenge collapsar cc short consequently type attack got name cc attack smurf attack relies misconfigured network devices allow packets sent computer hosts particular network via broadcast address network rather specific machine attacker send large numbers ip packets source address faked appear address victim devices network default respond sending reply source ip address number machines network receive respond packets large victim computer flooded traffic overloads victim computer even make unusable attack ping flood based sending victim overwhelming number ping packets usually using ping command unix-like hosts -t flag windows systems much less capable overwhelming target also -l size flag allow sent packet size greater 65500 windows simple launch primary requirement access greater bandwidth victim ping death based sending victim malformed ping packet lead system crash vulnerable system blacknurse attack example attack taking advantage required destination port unreachable icmp packets nuke old denial-of-service attack computer networks consisting fragmented otherwise invalid icmp packets sent target achieved using modified ping utility repeatedly send corrupt data thus slowing affected computer comes complete stop specific example nuke attack gained prominence winnuke exploited vulnerability netbios handler windows 95 string out-of-band data sent tcp port 139 victim machine causing lock display blue screen death bsod attackers found way exploit number bugs peer-to-peer servers initiate ddos attacks aggressive peer-to-peer-ddos attacks exploits dc++ peer-to-peer botnet attacker communicate clients subverts instead attacker acts puppet master instructing clients large peer-to-peer file sharing hubs disconnect peer-to-peer network connect victim website instead permanent denial-of-service pdos also known loosely phlashing attack damages system badly requires replacement reinstallation hardware unlike distributed denial-of-service attack pdos attack exploits security flaws allow remote administration management interfaces victim hardware routers printers networking hardware attacker uses vulnerabilities replace device firmware modified corrupt defective firmware image—a process done legitimately known flashing therefore bricks device rendering unusable original purpose repaired replaced pdos pure hardware targeted attack much faster requires fewer resources using botnet root/vserver ddos attack features potential high probability security exploits network enabled embedded devices needs technique come attention numerous hacking communities brickerbot piece malware targeted iot devices used pdos attacks disable targets phlashdance tool created rich smith employee hewlett-packard systems security lab used detect demonstrate pdos vulnerabilities 2008 eusecwest applied security conference london distributed denial-of-service attack may involve sending forged requests type large number computers reply requests using internet protocol address spoofing source address set targeted victim means replies go flood target reflected attack form sometimes called drdos icmp echo request attacks smurf attack considered one form reflected attack flooding host send echo requests broadcast addresses mis-configured networks thereby enticing hosts send echo reply packets victim early ddos programs implemented distributed form attack amplification attacks used magnify bandwidth sent victim typically done publicly accessible dns servers used cause congestion target system using dns response traffic many services exploited act reflectors harder block others us-cert observed different services implies different amplification factors tabulated dns amplification attacks involve new mechanism increased amplification effect using much larger list dns servers seen earlier process typically involves attacker sending dns name look request public dns server spoofing source ip address targeted victim attacker tries request much information possible thus amplifying dns response sent targeted victim since size request significantly smaller response attacker easily able increase amount traffic directed target snmp ntp also exploited reflector amplification attack example amplified ddos attack network time protocol ntp command called monlist sends details last 600 hosts requested time ntp server back requester small request time server sent using spoofed source ip address victim results response 556.9 times size request sent victim becomes amplified using botnets send requests spoofed ip source result massive amount data sent back victim difficult defend types attacks response data coming legitimate servers attack requests also sent udp require connection server means source ip verified request received server order bring awareness vulnerabilities campaigns started dedicated finding amplification vectors led people fixing resolvers resolvers shut completely attack works using worm infect hundreds thousands iot devices across internet worm propagates networks systems taking control poorly protected iot devices thermostats wi-fi enabled clocks washing machines device becomes enslaved usually owner user immediate indication iot device direct target attack used part larger attack newly enslaved devices called slaves bots hacker acquired desired number bots instruct bots try contact isp october 2016 mirai botnet attacked dyn isp sites twitter netflix etc soon occurred websites unreachable several hours type attack physically damaging certainly costly large internet companies get attacked rudy attack targets web applications starvation available sessions web server much like slowloris rudy keeps sessions halt using never-ending post transmissions sending arbitrarily large content-length header value manipuling maximum segment size selective acknowledgement sack may used remote peer cause denial service integer overflow linux kernel causing even kernel panic jonathan looney discovered cve-2019-11477 cve-2019-11478 cve-2019-11479 june 17 2019 shrew attack denial-of-service attack transmission control protocol uses short synchronized bursts traffic disrupt tcp connections link exploiting weakness tcp re-transmission timeout mechanism slow read attack sends legitimate application layer requests reads responses slowly thus trying exhaust server connection pool achieved advertising small number tcp receive window size time emptying clients tcp receive buffer slowly causes low data flow rate sophisticated low-bandwidth ddos attack form dos uses less traffic increases effectiveness aiming weak point victim system design i.e. attacker sends traffic consisting complicated requests system essentially sophisticated ddos attack lower cost due use less traffic smaller size making difficult identify ability hurt systems protected flow control mechanisms syn flood occurs host sends flood tcp/syn packets often forged sender address packets handled like connection request causing server spawn half-open connection sending back tcp/syn-ack packet acknowledge waiting packet response sender address response ack packet however sender address forged response never comes half-open connections saturate number available connections server make keeping responding legitimate requests attack ends teardrop attack involves sending mangled ip fragments overlapping oversized payloads target machine crash various operating systems bug tcp/ip fragmentation re-assembly code windows 3.1x windows 95 windows nt operating systems well versions linux prior versions 2.0.32 2.1.63 vulnerable attack although september 2009 vulnerability windows vista referred teardrop attack targeted smb2 higher layer tcp packets teardrop used one fields ip header “ fragment offset ” field indicating starting position offset data contained fragmented packet relative data original packet sum offset size one fragmented packet differs next fragmented packet packets overlap happens server vulnerable teardrop attacks unable reassemble packets resulting denial-of-service condition voice ip made abusive origination large numbers telephone voice calls inexpensive readily automated permitting call origins misrepresented caller id spoofing according us federal bureau investigation telephony denial-of-service tdos appeared part various fraudulent schemes telephony denial-of-service exist even without internet telephony 2002 new hampshire senate election phone jamming scandal telemarketers used flood political opponents spurious calls jam phone banks election day widespread publication number also flood enough calls render unusable happened accident 1981 multiple +1-area code-867-5309 subscribers inundated hundreds misdialed calls daily response song 867-5309/jenny tdos differs telephone harassment prank calls obscene phone calls number calls originated occupying lines continuously repeated automated calls victim prevented making receiving routine emergency telephone calls related exploits include sms flooding attacks black fax fax loop transmission takes router resources drop packet ttl value 1 less forward packet higher ttl value packet dropped due ttl expiry router cpu must generate send icmp time exceeded response generating many responses overload router cpu attack uses existing vulnerability universal plug play upnp protocol get around considerable amount present defense methods flood target network servers attack based dns amplification technique attack mechanism upnp router forwards requests one outer source another disregarding upnp behavior rules using upnp router returns data unexpected udp port bogus ip address making harder take simple action shut traffic flood according imperva researchers effective way stop attack companies lock upnp routers defensive responses denial-of-service attacks typically involve use combination attack detection traffic classification response tools aiming block traffic identify illegitimate allow traffic identify legitimate list prevention response tools provided application front-end hardware intelligent hardware placed network traffic reaches servers used networks conjunction routers switches application front end hardware analyzes data packets enter system identifies priority regular dangerous 25 bandwidth management vendors approaches ddos attacks cloud-based applications may based application layer analysis indicating whether incoming bulk traffic legitimate thus triggering elasticity decisions without economical implications ddos attack approaches mainly rely identified path value inside application monitor progress requests path markers called key completion indicators essence technique statistical methods assessing behavior incoming requests detect something unusual abnormal going analogy bricks-and-mortar department store customers spend average known percentage time different activities picking items examining putting back filling basket waiting pay paying leaving high-level activities correspond key completion indicators service site normal behavior determined abnormal behavior identified mob customers arrived store spent time picking items putting back never made purchases could flagged unusual behavior department store attempt adjust periods high activity bringing reserve employees short notice routinely mob start showing never buying anything could ruin store extra employee costs soon store would identify mob activity scale back number employees recognising mob provides profit served may make difficult legitimate customers get served mob presence saves store total ruin case elastic cloud services huge abnormal additional workload may incur significant charges cloud service provider technique used scale back even stop expansion server availability protect economic loss blackhole routing traffic attacked dns ip address sent black hole null interface non-existent server efficient avoid affecting network connectivity managed isp dns sinkhole routes traffic valid ip address analyzes traffic rejects bad packets sinkholing efficient severe attacks intrusion prevention systems ips effective attacks signatures associated however trend among attacks legitimate content bad intent intrusion-prevention systems work content recognition block behavior-based dos attacks asic based ips may detect block denial-of-service attacks processing power granularity analyze attacks act like circuit breaker automated way rate-based ips rbips must analyze traffic granularly continuously monitor traffic pattern determine traffic anomaly must let legitimate traffic flow blocking dos attack traffic focused problem ips dos defense system dds block connection-based dos attacks legitimate content bad intent dds also address protocol attacks teardrop ping death rate-based attacks icmp floods syn floods case simple attack firewall could simple rule added deny incoming traffic attackers based protocols ports originating ip addresses complex attacks however hard block simple rules example ongoing attack port 80 web service possible drop incoming traffic port prevent server serving legitimate traffic additionally firewalls may deep network hierarchy routers adversely affected traffic gets firewall also many security tools still support ipv6 may configured properly firewalls often might get bypassed attacks similar switches routers rate-limiting acl capability manually set routers easily overwhelmed dos attack cisco ios optional features reduce impact flooding switches rate-limiting acl capability switches provide automatic and/or system-wide rate limiting traffic shaping delayed binding tcp splicing deep packet inspection bogon filtering bogus ip filtering detect remediate dos attacks automatic rate filtering wan link failover balancing schemes work long dos attacks prevented using example syn flood prevented using delayed binding tcp splicing similarly content based dos may prevented using deep packet inspection attacks originating dark addresses going dark addresses prevented using bogon filtering automatic rate filtering work long set rate-thresholds set correctly wan-link failover work long links dos/ddos prevention mechanism traffic passed cleaning center scrubbing center via various methods proxies tunnels digital cross connects even direct circuits separates bad traffic ddos also common internet attacks sends good traffic beyond server provider needs central connectivity internet manage kind service unless happen located within facility cleaning center scrubbing center ddos attacks overwhelm type hardware firewall passing malicious traffic large mature networks becomes effective economically sustainable ddos unintentional denial-of-service occur system ends denied due deliberate attack single individual group individuals simply due sudden enormous spike popularity happen extremely popular website posts prominent link second less well-prepared site example part news story result significant proportion primary site regular userspotentially hundreds thousands peopleclick link space hours effect target website ddos attack vipdos specifically link posted celebrity michael jackson died 2009 websites google twitter slowed even crashed many sites servers thought requests virus spyware trying cause denial-of-service attack warning users queries looked like automated requests computer virus spyware application news sites link sitessites whose primary function provide links interesting content elsewhere internetare likely cause phenomenon canonical example slashdot effect receiving traffic slashdot also known reddit hug death digg effect routers also known create unintentional dos attacks d-link netgear routers overloaded ntp servers flooding ntp servers without respecting restrictions client types geographical limitations similar unintentional denials-of-service also occur via media e.g url mentioned television server indexed google another search engine peak periods activity lot available bandwidth indexed also experience effects dos attack legal action taken least one case 2006 universal tube rollform equipment corporation sued youtube massive numbers would-be youtube.com users accidentally typed tube company url utube.com result tube company ended spend large amounts money upgrading bandwidth company appears taken advantage situation utube.com containing ads advertisement revenue march 2014 malaysia airlines flight 370 went missing digitalglobe launched crowdsourcing service users could help search missing jet satellite images response overwhelmed company servers unintentional denial-of-service may also result prescheduled event created website case census australia 2016 could caused server provides service specific time might university website setting grades available result many login requests time computer network security backscatter side-effect spoofed denial-of-service attack kind attack attacker spoofs forges source address ip packets sent victim general victim machine distinguish spoofed packets legitimate packets victim responds spoofed packets normally would response packets known backscatter attacker spoofing source addresses randomly backscatter response packets victim sent back random destinations effect used network telescopes indirect evidence attacks term backscatter analysis refers observing backscatter packets arriving statistically significant portion ip address space determine characteristics dos attacks victims many jurisdictions laws denial-of-service attacks illegal january 7 2013 anonymous posted petition whitehouse.gov site asking ddos recognized legal form protest similar occupy protests claim similarity purpose
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Computer security
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vensim vensim simulation software developed ventana systems primarily supports continuous simulation system dynamics discrete event agent-based modelling capabilities available commercially free personal learning edition vensim provides graphical modeling interface stock flow causal loop diagrams top text-based system equations declarative programming language includes patented method interactive tracing behavior causal links model structure well language extension automating quality control experiments models called reality check modeling language supports arrays subscripts permits mapping among dimensions aggregation built-in allocation functions satisfy constraints sometimes met conventional approaches like logit supports discrete delays queues variety stochastic processes multiple paths cross sectional time-series data import export including text files spreadsheets odbc models may calibrated data using optimization kalman filtering markov chain monte carlo methods sensitivity analysis options provide variety ways test sample models including monte carlo simulation latin hypercube sampling vensim model files packaged published customizable read-only format executed freely available model reader allows sharing interactive models users program and/or model author wish access model code base vensim general-purpose software used wide variety problem domains common high-profile applications include
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Programming language topics
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service mapping description service mapping description smd proposed standard describing machine-readable json format web services available particular endpoint goal similar principle wsdl
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Web technology
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operating system abstraction layer operating system abstraction layer osal provides application programming interface api abstract operating system making easier quicker develop code multiple software hardware platforms os abstraction layers deal presenting abstraction common system functionality offered operating system means providing meaningful easy use wrapper functions turn encapsulate system functions offered os code needs porting well designed osal provides implementations api several real-time operating systems vxworks ecos rtlinux rtems implementations may also provided non real-time operating systems allowing abstracted software developed tested developer friendly desktop environment addition os apis os abstraction layer project may also provide hardware abstraction layer designed provide portable interface hardware devices memory i/o ports non-volatile memory facilitate use apis osals generally include directory structure build automation e.g. set makefiles facilitate building project particular os hardware platform implementing projects using osals allows development portable embedded system software independent particular real-time operating system also allows embedded system software developed tested desktop workstations providing shorter development debug time
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Operating systems
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dbeaver dbeaver sql client database administration tool relational databases uses jdbc api interact databases via jdbc driver databases nosql uses proprietary database drivers provides editor supports code completion syntax highlighting provides plugin architecture based eclipse plugins architecture allows users modify much application behavior provide database-specific functionality features database-independent desktop application written java based eclipse platform community edition ce dbeaver free open source software distributed apache license closed-source enterprise edition dbeaver distributed commercial license dbeaver started 2010 hobby project supposed free open-source good-looking convenient ui include frequently used features database developers first official release 2011 freecode quickly became popular tool open-source community year official web site founded community support forum moved github created 2012 eclipse plugin version released since dbeaver become one popular database extensions eclipse top 50-60 among eclipse extensions shortly various software vendors started integrate dbeaver mostly extensions proprietary eclipse rcp products zend studio nxtware deltadna etc. 2014 enterprise edition ee version released ee version based ce also provides support nosql/bigdata databases cassandra mongodb redis includes additional eclipse plugins 2015 dbeaver source code/community moved github 2017 dbeaver ce relicensed apache license starting version 4.x july 2017 dbeaver ee version became commercial order support ce version dbeaver cross-platform tool works platforms supported eclipse windows linux macos x solaris dbeaver available english chinese russian italian german full list released versions community edition ce initial version dbeaver released 2010 became open-source gpl 2011 ce version includes extended support following databases besides relational databases ce version supports wmi driver windows management instrumentation – works windows version year response multiple user requests eclipse plugin version released eclipse marketplace version used programmers use eclipse ide software development need database management tool right ide eclipse plugin includes features community edition also released gpl license dbeaver 3.x announced support nosql databases cassandra mongodb initial version since dbeaver divided community enterprise editions enterprise edition support nosql databases persistent query manager enterprise-level features ee version open-source requires purchase license trial license generated free charge list additional features dbeaver features include differences features available across different databases
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Databases
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lexical database lexical database lexical resource associated software environment database permits access contents database may custom-designed lexical information general-purpose database lexical information entered information typically stored lexical database includes lexical category synonyms words well semantic phonological relations different words sets words
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Computational linguistics
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envsys envsys framework kernel-level hardware monitoring sensors framework netbsd framework used close 85 device drivers export various environmental monitoring sensors evidenced references codice_1 symbol within codice_2 path netbsd temperature sensors codice_3 likely type exported given driver sensors registered kernel codice_4 api consumption monitoring sensors userland performed help codice_5 utility codice_6 codice_7 codice_8 pseudo-device file codice_9 power management daemon responds kernel events running scripts codice_10 well third-party tools like codice_11 gkrellm pkgsrc framework allows user amend monitoring limits specified driver driver perform monitoring sensors kernel space even programme hardware chip monitoring system automatically two levels limits defined critical warning additionally extend categorisation limit thresholds crossed kernel event may generated caught userland codice_9 execute pre-defined user script comparison openbsd hw.sensors monitoring user-defined values performed userspace codice_13 framework facilitate computer fan control although drivers could still implement interfacing fan-controlling capabilities chips means example driver-specific sysctl interface approach taken codice_14 driver however drivers popular super i/o chips like codice_15 codice_16 implement fan control fact historically openbsd netbsd dragonfly drivers n't even report duty cycle fans — actual rpm values reported framework undergone two major revisions first version codice_17 committed codice_18 man page following 2000 2007 manual page envsys 4 netbsd stated api experimental entire api replaced sysctl 8 one developed noted 2003 exact approach taken openbsd sysctl hw.sensors envsys 4 drivers ported openbsd second revision came serialisation userland reimplemented using property lists help netbsd new proplib 3 library underlying transport layer kernel userland still done ioctl envsys framework precursor openbsd sysctl hw.sensors framework 2003 many drivers well sensor types ported back forth netbsd openbsd support sensors codice_19 type added netbsd similar codice_19 type openbsd time bio 4 bioctl ported openbsd netbsd
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Operating systems
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trusted computing group trusted computing group group formed amd hewlett-packard ibm intel microsoft implement trusted computing concepts across personal computers trusted computing group announced 2003 successor trusted computing platform alliance previously formed 1999 many companies since joined trusted computing group including wave systems corp digital management inc. cisco lenovo infineon juniper networks fujitsu october 11 1999 trusted computing platform alliance abbreviated tcpa consortium various technology companies including compaq hewlett-packard ibm intel microsoft formed effort promote trust security personal computing platform november 1999 tcpa held founding conference announced 70 leading hardware software companies joined alliance since inception previous month january 30 2001 tcpa announced release version 1.0 trusted computing platform specifications aiming provide industry clear direction facilitates trust computing platforms environments december tcpa released version 1.1a trusted computing platform specifications ibm first original equipment manufacturer incorporate hardware features based version 1.1 tcpa trusted computing platform specifications introduction thinkpad t30 mobile computer april 24 2002 2003 tcpa succeeded trusted computing group increased emphasis trust mobile devices cell phones pdas tcg original goal development trusted platform module tpm semiconductor intellectual property core integrated circuit conforms trusted platform module specification put forward trusted computing group included computers enable trusted computing features tcg-compliant functionality since integrated directly certain mass-market chipsets tcg also recently released first version trusted network connect tnc protocol specification based principles aaa adding ability authorize network clients basis hardware configuration bios kernel version updates applied os anti-virus software etc 2009 tcg released set specifications describe protocol communicate self encrypting disk drives tcg storage work group swg storage core architecture specification describes detail implement utilize trust security services storage devices security subsystem class ssc specifications describe requirements specific classes devices specifically enterprise ssc defines minimum requirements data center server class devices opal ssc defines minimum requirements client devices vendor tpm-enabled system complete control software run owner system cases vendor may choose grant permission owner configure hardware legally purchased conversely restrict owner fully using property include possibility operating system os whether chosen user preinstalled hardware purchase refuses load unsigned unlicensed software e.g. microsoft described detail restrictions would enforced operating system tcg technology tpm provide case capability os lock software specific machine configurations meaning hacked versions os designed get around restrictions would work legitimate concern os vendors could use capabilities restrict software would load os hurting small software companies open source/shareware/freeware providers causing vendor lock-in data formats microsoft already stated begin restricting software allow run windows starting windows 8 arm tpm used conjunction boot loader ensure vendor-approved operating systems running could restrict alternative operating systems running including free open source operating systems example microsoft requiring x86/x64 machines come windows 8 secure boot enabled default caused alternative os vendors make payments microsoft ensure os able installed user additionally arm machine shipped windows 8 banned allowing another os installed time several projects experimenting tpm support free operating systems examples projects include tpm device driver linux open source implementation tcg trusted software stack called trousers also ported windows vista windows 7 2010 java interface tpm capabilities called tpm/j tpm-supporting version grub bootloader called trustedgrub tpm 1.1 specification envisioned standard pc platform equipped tpm chip scenario tpm chip serve hardware key storage additionally keep track so-called measurements platform i.e hashes various software able produce signed statements running software chain particularly latter mode operation proved unfeasible practice since amount software measured trusted large includes addition system firmware operating system drivers application programs therefore numerous tpm-related projects progress purpose make possible launch measure trusted subenvironment within untrusted environment tpm specification 1.2 enhanced accommodate mode operation additionally hardware changes required cpu chipset note confused inclusion tpm functionality chipset even though possibility intel approach called trusted execution technology txt many intel core 2 duo cpus advertised support extensions however chipset support required extensions operational currently intel chipset q35 express supports txt addition chipset support mainboard must also feature tpm 1.2 chip intel currently advertises dq35mp dq35jo compliant technology first application technology set manageability enhancements brand name vpro amd platform called secure execution mode 2002-2003 microsoft announced initiative called next-generation secure computing base formerly palladium basically vision tpm 1.2 chip cpu chipset software could provide environment software ecosystem trusted applications launched within regular windows could developed intel txt amd sem seen realizations hardware side ngscb vision owing significant difficulties creating working implementation third-party developers interested using unavailability enhancements cpu chipset ngscb included microsoft windows vista instead vista ships technologies make use subset functions tpm chip intel txt amd sem bitlocker drive encryption new version microsoft cryptography api group faced widescale opposition free software community grounds technology developing negative impact users privacy create customer lock-in especially used create drm applications received criticism gnu/linux freebsd communities well software development community general significant backlash amongst trusted computing group present richard stallman speech hackers planet earth conference july 2006 new york richard stallman free software foundation also criticized group publicly speeches criticism calls trusted computing treacherous computing instead warns vendors lock software officially signed specific vendors rendering unusable privacy concerns tcg revolve around fact tpm unique keypair called endorsement key identifies platform initial versions tpm version 1.1 tcg addressed privacy concerns suggesting use privacy ca could certify pseudonymous machine credentials separate credentials interacting different parties actions could linked level privacy provided however requires trust privacy ca could still link pseudonyms common identifying machine credential since left unresolved privacy concerns version 1.2 tpm specification introduced direct anonymous attestation protocol based idea zero-knowledge proof allows tpm user receive certification way privacy ca would able link requests single user platform still able identify rogue tpms privacy concerns tpm heightened christopher tarnovsky presented methods access compromise infineon tpm non-volatile memory capacity contains user data black hat 2010 efforts tcg specifications standardized iso active first part october 2007 member states iso/dis jtc1 expected send opinion iso july 24 2008 may 18 2009 tcg managed achieve standardization tpm specifications august 2014 approximately 100 promoters contributors adopters tcg specifications membership fees vary level promoters pay annual membership fees 30,000 contributors pay 15,000 depending upon company size adopters pay annual membership fees either 2,500 7,500
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Computer security
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dependency hell dependency hell colloquial term frustration software users installed software packages dependencies specific versions software packages dependency issue arises around shared packages libraries several packages dependencies depend different incompatible versions shared packages shared package library installed single version user may need address problem obtaining newer older versions dependent packages turn may break dependencies push problem another set packages dependency hell takes several forms specific computing platforms dependency hell often goes local specific name generally name components
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Operating systems
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executable choreography executable choreography represents decentralized form service composition involving cooperation several individual entities improved form service choreography executable choreographies intuitively seen arbitrary complex workflows get executed systems belonging multiple organisations authorities executable choreographies actual code created encode system behavior global point view behavior main entities system given single program choreographies enhance quality software behave like executable blueprints communicating systems behave offer concise view message flows enacted system almost applications business logic must separated different services orchestration represents way services organized composed resulting service integrated hierarchically another composition service choreography global description participating services defined exchange messages rules interaction agreements two endpoints choreography employs decentralized approach service composition industry concept choreography generally considered non-executable standards proposed web services choreography description language present choreography formal model describe contracts autonomous entities generally distinct organizations participating composition services analyzed globally perspective composition must implemented centrally different orchestration mechanisms made available companies naive code composition use specific orchestration languages engines bpel business process execution language rule engines etc area academic research concept executable choreography proposed method longer contractual part actual part code two different artifacts non-synchronized require subjective interpretations examples executable calculus service choreography executable choreography framework dynamic service-oriented architectures approaches also practical impact often level articles least research projects real breakthrough blockchain recent years brought even attention academic community industry concept smart contract seen particular form executable choreography executable choreographies general concept necessarily verifiable choreographies use idea site regarded security context code execution examples approaches programming using executable choreographies could list european project choreos chor programming language web service modeling choreographing web services aspects related composition web services using pi-calculus verifiable term introduced highlight possibility verifying swarm choreographies explicit presence execution location idea leads possibility developing verification algorithms seen article levels privacy e-health systems cloud era encrypted cryptography supposes addition verification offer higher-level solutions advanced cryptographic methods without need programmers become cryptography specialists distributed applications could built subsystems allow identification verification architectural points expose secret data example ideally programming system uses encrypted choreographs guarantees least helps minimize situations person legally licensed hacker holds encrypted private data encryption keys related resources way administrators programmers subsystems fewer possibilities perform internal attacks privacy level frequent attacks even applications use approach encrypted choreographies minimize security risks caused people inside administer program systems thus number points discreet access data ideally never formally ensured form choreography useful allow companies secure code application legislation security rules assumed implementation encrypted choreographies implies example existence storage systems using cryptographic techniques practical implementation homomorphic encryption cryptdb implementation mit method also called storage division anonymization method help encrypted choreographies lead ideal total sovereignty within limits law private data published article private data system enabling self-sovereign storage managed executable choregraphies paper presents choreographies anonymize divide data way ensures data copied single administrator hacker controls one participating nodes implemented mechanisms also include interfaces easy use programmers advanced cryptographic methods serverless computing cloud computing model cloud provider dynamically manages allocation computing resources serverless choreographies involve automating launching methods using virtualization automation techniques implementation advanced type choreography requires development new business models facilitate cloud-based application hosting without friction related payment installation etc example tor concept provides example serverless systems best known example amazon lambda great commercial success allowing programmers ignore installation details facilitate dynamic scalability systems blockchains considered examples serverless databases serverless choreographies assume cloud execution storage done using encrypted choreographies using form choreography hosting companies individuals managing physical logical hosting infrastructure able influence hosted installation applications serverless choreographies present opportunity develop distributed decentralized systems potential formally secure advanced privacy properties
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Web technology
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lew allen lew allen jr. september 30 1925 – january 4 2010 united states air force four-star general served tenth chief staff united states air force chief staff allen served senior uniformed air force officer responsible organization training equipping 750,000 active duty air force air national guard air force reserve civilian personnel serving united states overseas member joint chiefs staff service chiefs function ed military advisers secretary defense national security council president born miami florida allen attended graduated high school gainesville texas 1942 entered united states military academy 1943 graduated 1946 bachelor science degree commission second lieutenant awarded pilot wings upon graduation flight training completing multi-engine flight training november 1946 allen assigned strategic air command 7th bombardment group carswell air force base texas flew b-29 superfortress bombers new long-range convair b-36 bomber allen also served various technical positions area nuclear weapons allen also attended air tactical course tyndall air force base florida next returned carswell air force base flight instructor assistant special weapons officer 7th bombardment wing september 1950 allen entered university illinois graduate study nuclear physics completed master science degree 1952 allen continued graduate study earned ph.d. physics 1954 completed experimental thesis high-energy photonuclear reactions allen assigned u.s. atomic energy commission los alamos scientific laboratory los alamos new mexico physicist test division became acquainted bomb designer ted taylor allen conducted experiments several different nuclear test series experiments concerned physics thermonuclear weapons design effects high altitude nuclear explosions conceivably used ballistic missile defense june 1957 december 1961 allen assigned kirtland air force base new mexico science adviser physics division air force special weapons center special weapons euphemism nuclear thermonuclear bombs allen specialized military effects high altitude nuclear explosions participated several nuclear weapons test series scientific director major experiment utilized large series high altitude rockets measure characteristics electrons trapped geomagnetic field exoatmospheric nuclear burst allen assigned december 1961 office secretary defense space technology office directorate research engineering washington d.c. june 1965 february 1973 assigned office secretary air force initially los angeles california deputy director advanced plans directorate special projects allen next moved pentagon june 1968 deputy director space systems june 1969 became director returned los angeles september 1970 assistant director special projects april 1971 became director special projects additional duty deputy commander satellite programs space missile systems organization serving briefly chief staff air force systems command andrews air force base maryland allen appointed march 1973 deputy director central intelligence intelligence community washington d.c august 1973 allen became director national security agency nsa chief central security service fort george g. meade maryland allen tenure nsa director noteworthy became first director ever testify publicly congress august 1977 named commander air force systems command allen served vice chief staff united states air force april 1978 became chief staff air force july 1978 nomination unusual never served overseas combat assignment positions specialized technical activities rather usual command structure air force also last chief staff bomber background subsequent chiefs staff except general norton schwartz fighter pilots trend reflected service weapon budgets devote funding fighters rather bombers following retirement air force 1982 allen became director jet propulsion laboratory jpl part voyager program space probes launched 1977 served director jpl 1990 allen member national academy engineering council foreign relations 1993 1995 allen served member president foreign intelligence advisory board pfiab intelligence oversight board allen awarded 1999 distinguished graduate award association graduates alumni association west point graduates allen died potomac falls virginia january 4 2010 complications rheumatoid arthritis buried arlington national cemetery march 22 2010 united states air force created general lew allen jr. trophy allen honor awarded annually officer senior nco aircraft maintenance munitions career fields directly involved setting aircraft sorties since 1986 jet propulsion laboratory awards honor lew allen award excellence 1990 called director research achievement award
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Computer security
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hp pre 3 hp pre 3 styled pre touchscreen slider smartphone manufactured hewlett-packard device uses webos powered qualcomm snapdragon processor 3.6-inch screen conceptually successor palm pre 2 earlier pre pre plus models hp pre 3 announced february 9 2011 hp webos think beyond event held fort mason center san francisco alongside veer touchpad commercially released united kingdom august 17 2011 device supports new touch-to-share proximity-based sharing feature allows compatible devices touchpad instantly exchange data media information via bluetooth pre 3 802.11 a/b/g/n wi-fi 512 mb ram 8 gb internal storage bluetooth v2.1 1230 mah battery 16 gb model manufactured verizon united states models never released general public pre 3 released august 17 2011 united kingdom next day august 18 hp announced would discontinuing webos devices including pre 3 phone never officially released united states although models eventually sold hp employee store california many phones ended ebay auctions hp pre 3 features 3.58-inch multi-touch capacitive touchscreen resolution 800-by-480 pixels pre 3 three physical buttons input including volume up/down buttons side power button top navigating os pre 3 gesture area swipe enter card like multitasking view swipe right left go back application swipe left right go forward optionally swipe completely right left switch applications modifier keys combined gestures enable text selection cursor positioning command shortcuts triggered holding tap gesture area pressing key keyboard pre 3 supports bluetooth 2.1 802.11a/b/g/n wifi hspa+ well gsm evdo cdma depending service provider along hp touchpad pre 3 supports new technology called touch share touch share lets share urls phone calls text messages data 3rd party apps touchpad hp pre 3 tapping phone touchpad sensor example web site browsed touchpad transferred pre browser tapping two devices together umts frequency bands supported pre 3 mono loudspeaker well dual mic noise cancellation pre 3 features 5 mega pixel camera auto focus led flash capable 720p video recording phone also front-facing vga camera video calling integrated skype application pre 3 sold carphone warehouse uk competitive pay monthly contract terms limited available stock us gsm models sold direct hp employees 75 12 per employee branded unsupported either hp/palm though received over-the-air ota update 2.2.0 2.2.3 addition update webos 2.2.4 released update webos doctor ota update
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Operating systems
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geom geom main storage framework freebsd operating system available freebsd 5.0 higher provides standardized way access storage layers geom modular allows geom modules connect framework example geom_mirror module provide raid1 mirroring functionality system wide range modules already available new ones always active development various freebsd developers geom developed freebsd project poul-henning kamp nai labs security research division network associates inc. darpa/spawar contract n66001-01-c-8035 cboss part darpa chats research program name symbolizes impact disk geometry geom modular design modules 'stacked together form chain geom layers example top geom_mirror module encryption module added geom_eli provide mirrored encrypted volume module consumers providers provider 'source geom module often physical hard drive sometimes virtualized disk memory disk geom module turn provides 'output device geom modules called consumers use provider create chain modules connected source → geom module → output referred provider → geom module → consumer example geom_mirror module may use consumer following providers /dev/ada0 /dev/ada1 creates provider new device called /dev/mirror/gm0 end geom chain often filesystem applied actually use geom provider something useful provider created geom modules behaves like physical hard drive contain filesystems freebsd native unix file system ufs storage modules encryption compression modules filesystem modules virtualization
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Operating systems
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c.mmp c.mmp early mimd multiprocessor system developed carnegie mellon university william wulf 1971 notation c.mmp came pms notation bell newell cpu designated c variant noted dot notation mmp stood multi-mini-processor sixteen pdp-11 minicomputers used processing elements named compute modules system cm local memory 8k local set peripheral devices one challenges device available unique connected processor i/o system designed roy levin hid connectivity devices routed requests hosting processor processor went devices connected unibus became unavailable became problem overall system reliability processor 0 boot processor disk drives attached compute modules shared communication pathways since pdp-11 address space 16-bits additional address translation unit added expand address space 25 bits shared memory space unibus architecture provided 18 bits address two high-order bits used select one four relocation registers selected bank memory proper management relocation registers one challenges programming operating system kernel original c.mmp design used magnetic core memory lifetime higher performance dynamic ram became available system upgraded original processors pdp-11/20 processors final system five used remaining 11 pdp-11/40 processors modified additional writeable microcode space modifications machines designed built cmu 11/20 modifications custom changes motherboard pdp-11/40 implemented microcode separate proc-mod board designed intercepted certain instructions implemented protected operating system requirements example necessary operating system integrity stack pointer register never odd 11/20 accomplished clipping lead low-order bit stack register 11/40 access stack intercepted proc-mod board generated illegal data access trap low-order bit 1 operating system called hydra capability-based object-oriented multi-user operating system system resources represented objects protected capabilities among programming languages available system subset algol 68 language fact superset subset features supporting parallelism vastly improved make good use c.mmp operating system applications written language bliss-11 required cross-compilation pdp-10 algol-68 compiler ran native hydra operating system little assembly code used operating system overall system reliability depended 16 cpus running serious problems overall hardware reliability mtbf one processor 24 hours overall system reliability 16/24 hours 40 minutes overall system usually ran two six hours many failures due timing glitches many custom circuits added processors considerable effort expended getting hardware reliability improved processor noticeably failing partitioned would run diagnostics several hours passed first set diagnostics partitioned back i/o processor would run application code peripheral devices available continued run diagnostics passed several hours reinstated full member processor set similarly block memory one page detected faulty removed pool available pages otherwise notified operating system would ignore page thus operating system became early example fault-tolerant system able deal hardware problems would inevitably arise machine display ninth floor wean hall carnegie mellon university
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Computer architecture
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black fax term black fax refers prank fax transmission consisting one pages entirely filled uniform black tone sender intention generally use much recipient fax ink toner thermal paper possible thus costing recipient money well denying recipient use machine similar computer-based denial service attacks made easier fax transmission protocols compress solid black image well short fax call produce many pages black faxes used harass large institutions government departments retaliate senders junk faxes merely simple pranks basic principle black fax extended form black fax attack case one sheets fed halfway sender fax machine taped end end forming endless loop cycles machine solid black used also images repeat endlessly receiver machine toner runs introduction computer-based facsimile systems combined integrated document imaging solutions major corporations means black faxes unlikely cause problems hand ability computer modems send faxes offers new avenues abuse program could used generate hundreds pages highly compressed pure black – huge volumes relevant-looking original non-repeating high-black-density junk effective far difficult counteract – send quickly target fax machine black faxes fax loops similar intention implementation lace cards
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Computer security
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openserver xinuos openserver previously sco unix sco open desktop sco odt closed source computer operating system developed santa cruz operation sco later acquired sco group owned xinuos early versions openserver based unix system v later openserver 10 based freebsd sco unix successor santa cruz operation variant microsoft xenix derived unix system v release 3.2 infusion xenix device drivers utilities sco unix system v/386 release 3.2.0 released 1989 commercial successor sco xenix base operating system include tcp/ip networking x window system graphics available optional extra-cost add-on packages shortly release bare os sco shipped integrated product name sco open desktop odt 1994 saw release sco mpx add-on smp package time completed merge xenix bsd sunos unix system v release 3 features unix system v release 4 sco unix remained based system v release 3 eventually added home-grown versions features release 4 1992 releases sco unix 3.2v4.0 open desktop 2.0 added support long file names symbolic links next major version openserver release 5.0.0 released 1995 added support elf executables dynamically linked shared objects made many kernel structures dynamic sco openserver 5 released 1995 would become sco primary product serve basis products like pizzanet first internet-based food delivery system done partnership pizza hut sco global access internet gateway server based open desktop lite due large installed base sco openserver 5 continues actively maintained sco major updates occurred recently april 2009 sco openserver 6 based merging unix system v release 4.2mp novell unixware 7 initially released sco group 2005 includes support large files increased memory multi-threaded kernel light-weight processes merged codebase referred unix system v release 5 svr5 used sco openserver 6 svr5 used major developer reseller sco openserver 6 contains unixware 7 svr5 kernel integrated sco openserver 5 application binary compatibility openserver 5 system administration openserver 5 user environments sco openserver primarily sold small medium business smb market widely used small offices point sale pos systems replicated sites backoffice database server deployments prominent larger sco openserver customers include mcdonald taco bell big tires pizza hut costco pharmacy nasdaq toronto stock exchange banco brasil many banks russia china railway system india sco purchased right distribute unixware system system v release 4 code base novell 1995 sco eventually able re-use code version unixware later releases openserver release 6 came primarily compilation system udi driver framework usb subsystem written end 1990s around 15,000 value-added resellers vars around world provided solutions customers sco unix systems sco announced august 2 2000 would sell server software services divisions well unixware openserver technologies caldera systems inc purchase completed may 2001 remaining part sco company tarantella division changed name tarantella inc. caldera systems became caldera international subsequently 2002 sco group sco group continued development maintenance openserver currently continue maintain obsoleted 5.0.x branch derived 3.2v5.0.x recent 5.0.7 june 22 2005 openserver 6.0 released codenamed legend first release new 6.0.x branch sco openserver 6 based unix system v release 5 svr5 kernel merged codebase unix system v release 4.2mp unixware 7 openserver 6.0 features multi-threading application support c c++ java applications posix interface openserver 6 features kernel-level threading found 5.0.x improvements openserver 5 include improved smp support support 32 processors support files terabyte partition larger network files supported nfsv3 better file system performance support 64 gb memory openserver 6.0 maintains backward-compatibility applications developed xenix 286 onwards sco group went bankrupt 2011 long series legal battles rights openserver well unixware acquired unxis 2011 later renamed xinuos june 2015 xinuos announced openserver 10 based freebsd operating system simultaneously xinuos introduced migration path existing customers using older os products december 2015 xinuos released definitive versions openserver 5 openserver 6 unixware 7 december 2017 xinuos released definitive 2018 versions openserver 6 unixware 7 october 2018 openserver 5 definitive 2018 released definitive 2018 releases commitment xinuos keep legacy os updated supported protecting applications customers need continue run definitive 2018 products contain major updates definitive releases soon announced updated development kit make easier compile current packages definitive 2018 products xinuos continued provide updates new flag ship os openserver 10 working version 12 release openserver 10 2019
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Operating systems
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industry connections security group industry connections security group ieee icsg global group computer security entities past present members include anh labs avg avira eset f-secure k7 computing kaspersky labs marvell mcafee microsoft palo alto networks panda software safenet sophos symantec trend micro come together ieee pool experience resources combating systematic rapid rise computer security threats ieee icsg activities include
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Computer security
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unidirectional network unidirectional network also referred unidirectional gateway data diode network appliance device allows data travel one direction data diodes found commonly high security environments defense serve connections two networks differing security classifications given rise industrial iot digitization technology found industrial control level facilities nuclear power plants power generation safety critical systems like railway networks years development use data diodes increased creating two variations data diodes commonly found high security military government environments becoming widely spread sectors like oil gas water/wastewater airplanes flight control units in-flight entertainment systems manufacturing cloud connectivity industrial iot new regulations increased demand increased capacity major technology vendors lowered cost core technology first data diodes developed governmental organizations eighties nineties organizations work confidential information making sure network secure highest priority primary solutions used organizations air gaps amount transferable data increased continuous real-time data stream became important organizations look automated solution search standardization increasing number organizations started look solution better fit activities commercial solutions created stable organizations succeeded given level security long-term support us utilities oil gas companies used data diodes several years regulators encouraged use protect equipment processes siss nuclear regulatory commission nrc mandates use data diodes many sectors addition electrical nuclear also use data diodes effectively europe regulators operators several safety-critical systems started recommending implementing regulations use unidirectional gateways 2013 working industrial control system cybersecurity directed french network information security agency anssi stated forbidden use firewalls connect class 3 network railway switching systems lower class network corporate network unidirectional technology permitted unidirectional network devices typically used guarantee information security protection critical digital systems industrial control systems cyber attacks use devices common high security environments defense serve connections two networks differing security classifications technology also used enforce one-way communications outbound critical digital systems untrusted networks connected internet physical nature unidirectional networks allows data pass one side network connection another way around low side untrusted network high side trusted network vice versa first case data high side network kept confidential users retain access data low side functionality attractive sensitive data stored network requires connectivity internet high side receive internet data low side data high side accessible internet-based intrusion second case safety-critical physical system made accessible online monitoring yet insulated internet-based attacks might seek cause physical damage cases connection remains unidirectional even low high network compromised security guarantees physical nature two general models using unidirectional network connections classical model purpose data diode prevent export classified data secure machine allowing import data insecure machine alternative model diode used allow export data protected machine preventing attacks machine described detail involves systems must secured remote/external attacks public networks publishing information networks example election management system used electronic voting must make election results available public time must immune attack model applicable variety critical infrastructure protection problems protection data network less important reliable control correct operation network example public living downstream dam needs up-to-date information outflow information critical input control system floodgates situation critical flow information secure control system public vice versa majority unidirectional network applications category defense defense contractors organizations traditionally applied air gaps keep classified data physically separate internet connection introduction unidirectional networks environments degree connectivity safely exist network classified data network internet connection bell-lapadula security model users computer system create data security level applies contexts hierarchy information classifications users security level share machine dedicated level machines connected data diodes bell-lapadula constraints rigidly enforced traditionally network provides dmz server access authorized user data vulnerable intrusions network however unidirectional gateways separating critical side ot network sensitive data open side business internet connectivity normally network organizations achieve best worlds enabling connectivity required assuring security holds true even network compromised traffic flow control physical nature simplest form unidirectional network modified fiber-optic network link send receive transceivers removed disconnected one direction link failure protection mechanisms disabled commercial products rely basic design add software functionality provides applications interface helps pass data across link sophisticated commercial offerings enable simultaneous one-way data transfer multiple protocols usually require bidirectional links owl cyber defense offered specialized government defense data diode solutions since late 1990s well solutions critical infrastructure commercial applications recently low-cost iot security data diode 2018 siemens mobility released industrial grade unidirectional gateway solution data diode data capture unit uses electromagnetic induction new chip design achieve eba safety assessment guaranteeing secure connectivity new existing safety critical systems safety integrity level sil 4 enable secure iot provide data analytics cloud hosted digital services us naval research laboratory nrl developed unidirectional network called network pump many ways similar dsto work except allows limited backchannel going high side low side transmission acknowledgments technology allows protocols used network introduces potential covert channel high- low-side compromised artificially delaying timing acknowledgment different implementations also differing levels third party certification accreditation cross domain guard intended use military context may require extensive third party certification accreditation data diode intended industrial use however may require third party certification accreditation depending application
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Computer security
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chung laung liu professor chung laung dave liu 劉炯朗 c. l. liu ethnic chinese computer scientist born guangzhou spent childhood macau received b.sc degree taiwan master degree doctorate united states liu received b.sc degree 1956 national cheng kung university taiwan s.m e.e degrees 1960 sc d. degree 1962 massachusetts institute technology faculty massachusetts institute technology 1962–1972 university illinois urbana-champaign 1972–1998 associate provost 1995 1998 retired uiuc served president professor computer science national tsing hua university nthu hsinchu taiwan february 1998 february 2002 currently william mong honorary chair professor national tsing hua university visiting professor city university hong kong waseda university tokyo japan li k. t. honorary chair professor national central university since 2007 li kuo-ting forum professor national cheng kung university author co-author seven books monographs 180 technical papers research interests include computer-aided design vlsi circuits real-time systems computer-aided instruction combinatorial optimization discrete mathematics received ieee millennium medal ieee circuits systems society golden jubilee medal 2000 also received ieee computer society real time systems technical committee 1999 technical achievement award inaugural winner contributions area real time scheduling ieee circuits systems society 1998 technical achievement award contributions area computer aided design vlsi circuits received outstanding talents foundation award 1998 recipient 1994 ieee education medal also received taylor l. booth education award ieee computer society 1992 inaugural winner karl v. karlstrom education award association computing machinery 1989 member academia sinica fellow institute electrical electronics engineers fellow association computing machinery 2004 university macau awarded honorary doctorate
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Computer architecture
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tsinghua university tsinghua university abbreviated thu also romanized qinghua major research university beijing member elite c9 league chinese universities since establishment 1911 graduated numerous chinese leaders politics business academia culture reflecting motto self-discipline social commitment tsinghua university dedicated academic excellence advancing well-being chinese society global development along nearby peking university tsinghua perennially ranked one top academic institutions china asia worldwide recognized 14th best university 2017 times higher education world reputation rankings since 2015 tsinghua ranked best engineering computer science school world based factors including total research output performance tsinghua class institution double first class university plan tsinghua university established beijing tumultuous period national upheaval conflicts foreign powers culminated boxer rebellion anti-imperialist uprising foreign influence china suppression revolt foreign alliance including united states ruling qing dynasty required pay indemnities alliance members us secretary state john hay suggested us 30 million boxer indemnity allotted united states excessive much negotiation qing ambassador liang cheng us president theodore roosevelt obtained approval united states congress 1909 reduce indemnity payment us 10.8 million condition funds would used scholarships chinese students study united states using fund tsinghua college established beijing 29 april 1911 site former royal garden serve preparatory school students government planned send united states faculty members sciences recruited ymca united states graduates transferred directly american schools juniors upon graduation motto tsinghua self-discipline social commitment derived 1914 speech prominent scholar faculty member liang qichao quoted ching describe notion ideal gentleman 1925 school established four-year undergraduate program started research institute chinese studies 1928 tsinghua changed name national tsing hua university nthu second sino-japanese war many chinese universities forced evacuate campuses avoid japanese invasion 1937 tsinghua university along neighboring peking university nankai university merged form changsha temporary university changsha later became national southwestern associated university kunming yunnan province surrender occupying japanese forces end world war ii tsinghua university resumed operations beijing end chinese civil war 1949 china experienced communist revolution leading creation people republic china tsinghua university president mei yiqi along many professors fled taiwan retreating nationalist government established national tsing hua institute nuclear technology 1955 later became national tsing hua university taiwan institution independent distinct tsinghua university 1952 communist party china regrouped country higher education institutions attempt build soviet style system institution specialized certain field study social sciences natural sciences tsinghua university streamlined polytechnic institute focus engineering natural sciences 1966 1976 china experienced immense sociopolitical upheaval instability cultural revolution many university students walked classrooms tsinghua institutions went join red guards resulting complete shutdown university faculty persecuted otherwise unable teach 1978 cultural revolution ended university began take students re-emerge force chinese politics society 1980s tsinghua evolved beyond polytechnic model incorporated multidisciplinary system emphasizing collaboration distinct schools within broader university environment system several schools re-incorporated including tsinghua law school school economics management school sciences school life sciences school humanities social sciences school public policy management academy arts design 1996 school economics management established partnership sloan school management massachusetts institute technology one year later tsinghua mit began mba program known tsinghua-mit global mba 1997 tsinghua became first chinese university offer master laws llm program american law cooperative venture temple university beasley school law since resuming operations 1978 tsinghua university re-established among elite chinese universities affiliated c9 league selected participate double first class university plan national international university rankings consistently place tsinghua among best universities greater china asia worldwide tsinghua alumni include current general secretary chinese communist party paramount leader china xi jinping '79 graduated degree chemical engineering along cpc general secretary former paramount leader china hu jintao '64 graduated degree hydraulic engineering addition powerful alumni tsinghua reputation hosting globally prominent guest speakers international leaders bill clinton tony blair henry kissinger carlos ghosn park geun-hye henry paulson lectured university community 2018 tsinghua university consists 20 schools 58 university departments 41 research institutes 35 research centers 167 laboratories including 15 national key laboratories september 2006 peking union medical college renowned medical school renamed peking union medical college tsinghua university although tsinghua university technically separate institutions university operates tsinghua university press publishes academic journals textbooks scholarly works constituent colleges graduate professional schools institutes tsinghua university offers 51 bachelor degree programs 139 master degree programs 107 phd programs university consistently pursued innovation undergraduate graduate education partnerships foreign universities creation new colleges high-profile scholarship programs 2014 tsinghua established xinya college residential liberal arts college pilot project reform undergraduate education university modeled universities united states europe xinya combines general professional education liberal arts tradition featuring core curriculum chinese western literature civilization studies required courses physical education foreign languages furthermore tsinghua undergraduates must choose specific major upon entrance xinya students declare majors end freshman year enabling explore several different fields study tsinghua university also aggressively pursuing greater recognition global stage attracting funding talented international graduate students established 2013 us 300 million endowment modeled rhodes scholarship schwarzman scholars program annually selects funds 200 scholars enrolled one-year master degree programs public policy international relations engineering economics business scholars reside university campus schwarzman college residential college built specifically program 2016 tsinghua expenditures rmb 13.7 billion us 3.57 billion purchasing power parity largest budget university china tsinghua university engages extensive research offers 51 bachelor degree programs 139 master degree programs 107 doctoral programs 20 colleges 57 departments covering broad range subjects including science engineering arts literature social sciences law medicine along membership c9 league tsinghua university affiliations include association pacific rim universities group 50 leading asian american universities washington university st. louis ’ mcdonnell international scholars academy group 35 premier global universities association east asian research universities 17-member research collaboration network top regional institutions tsinghua associate member consortium linking universities science technology education research cluster admission tsinghua undergraduate graduate schools extremely competitive undergraduate admissions domestic students decided gaokao chinese national college entrance exam allows students list tsinghua university among preferred college choices selectivity varies province sheer number high school students applying college year resulted overall acceptance rates far lower 0.1 test takers tsinghua university commands high rate matriculation accepted undergraduates according report 2008 215 300 students placed within top 10 30 tested provinces regions chose tsinghua first choice school 21 30 top scorers province region chose university admission tsinghua graduate schools also competitive 16 mba applicants admitted year research tsinghua university mainly supported government funding national programs special projects areas science technology funding sources totals 20 billion yuan subsidizes 1,400 projects every year conducted university prospective increase state investment science technology research tsinghua projected receive financial support state year university hosts intellectual property summer institute cooperation franklin pierce law center concord new hampshire according domestic international rankings tsinghua university consistently recognized one top two universities mainland china along neighboring institution rival peking university example netbig chinese university rankings gave tsinghua 1st 2008 2009 2010 awarded 2nd china education center years internationally tsinghua regarded reputable chinese university 2017 times higher education world reputation rankings ranked 14th globally 2019 ranked 6th among universities around world scimago institutions rankings 2013 tsinghua also topped newly created regional qs brics university rankings 2015 us news world report best global university ranking ranked tsinghua 4th asia 59th globally sciences general 2018 cwts leiden ranking ranked tsinghua university 6th world time period 2013-2016 2014 ranked 23rd times higher education rankings subjects engineering technology historical strengths tsinghua since 2015 tsinghua university overtaken massachusetts institute technology top list best global universities engineering published u.s. news world report department electrical engineering tsinghua university plays pioneer role state power grid china research focus department include following areas department mathematical sciences dms established 1927 1952 tsinghua dms merged peking university department mathematical sciences 1979 renamed department applied mathematics renamed 1999 current title tsinghua dms three institutes present institute pure mathematics 27 faculty members institute applied mathematics probability statistics 27 faculty members institute computational mathematics operations research 20 faculty members currently 400 undergraduate students 200 graduate students department precision instrument called department precision instrument machine manufacturing 1960 separated department machine manufacturing independent department later 1971 renamed department precision instrument mission department precision instrument tsinghua university dean said supporting national development improving people ’ well-being research department precision instrument divided four main parts led four research institutes institute opto-electronic engineering institute instrument science technology engineering research center navigation technology center photonics electronics time department precision instrument three key laboratories state key laboratory tribology state key laboratory precision measurement technology instruments key laboratory high-accuracy inertial instrument system also two national engineering research centers national engineering research center optical disk cims national engineering research center institute opto-electronic engineering ioee established 1958 obtained chinese government authorization offer phd program 1981 approval build post-doctoral research site 1988 research ioee covers opto-electronic instruments precision metrology measurement modern optical information processing theory components binary optics birefringent frequency-splitting lasers several famous scientists work ioee including professor guofan jin academician chinese academy engineering professor kegong zhao formerly president chinese national institute metrology institute instrument science technology important institute state key laboratory precision measuring technology instrument science tsinghua university institute equipped advanced instruments facilities research included every major area modern instrument science technology 2012 institute produced 1500 publications 100 patents acquired many significant awards engineering research center navigation technology relatively young institute department precision instrument established 2000 intention pursue excellence research development field high-accuracy inertial instruments navigation technology well mems inertial sensor fields provide advanced training future scientists engineers field inertial technology research interests cover high-accuracy inertial instruments navigation technology mems inertial sensors systems precise electro-mechanical control systems application 2012 area center 2900 square meters including approximately 550 square meters clean rooms equipment instruments center worth 50 million rmb 7.56 million usd center photonics electronics works advanced laser photonic technology houses 200 square meters clean rooms modern laser instruments equipment research center covers solid-state laser technology fiber laser technology active optics technology laser detection technology center published lots papers also partnerships many domestic international companies research institutes authorization china state planning commission ministry education state key laboratory tribology sklt established november 1988 present director sklt professor yonggang meng present chair academic committee sklt professor jue zhong also member chinese academy engineering sklt one central laboratory 4 sub-laboratories awarded numerous awards including two national natural science awards two national invention awards one national award science technology progress two national excellent science book awards 25 awards ministries provinces china edmond e. bisson award 2003 stle 2008 pe publishing prize editor editorial board journal engineering tribology moreover china ministry education recognized sklt one creative groups 2005 national natural science foundation china recognized sklt one creative research groups 2007 established 1995 state key laboratory precision measurement technology instruments joint laboratory tsinghua university tianjin university national key laboratory two recognized national first-level key disciplines second-class disciplines research state key laboratory precision measurement technology instruments categorized four major parts laser optoelectric measurement technology sensing information measurement technology micro- nano- measurement fabrication technology quality control manufacturing technology key laboratory high-accuracy inertial instrument system established intention support research engineering research center navigation technology since establishment five prizes published large quantity papers currently two disciplines department precision instrument discipline instrumental science technology precision instrument mechanology discipline optical engineering six teaching laboratories centers serve significant roles undergraduate graduate education department precision instrument department provides 40 courses undergraduate level 25 courses graduate level 2012 284 undergraduates 152 postgraduates 219 doctoral students studying working department school life sciences first established 1926 name department biology botanist qian chongshu took first dean nationwide reorganization universities early 1950s department biology merged universities namely peking university etc. resulting vacancy field biological research tsinghua almost 30 years june 1984 decisions made reestablishment department biology department officially reopened september reestablishment department biology peking university institute biophysics chinese academy sciences many institutes well biologists provided valuable support help department changed name current name september 2009 2013 structural biologist foreign associate national academy sciences united states dr. yigong shi current dean school life sciences school currently 38 professors around 600 undergraduates including candidates tsinghua university peking union medical college joint md program 200 graduate students peking union medical college established 1917 rockefeller foundation modeled us medical education system tsinghua first established medical school 2001 2006 tsinghua medical school merged peking union medical college renaming peking union medical college tsinghua university school remains top ranked medical school general hospital china according cucas 2015 peking union medical college also medical school affiliated chinese academy medical sciences runs one competitive medical programs country accepting 90 students year 8-year md program students 8-year program spend 2.5 years tsinghua studying basic sciences moving onto peking union medical college complete last 5.5 years clinical medicine tsinghua school journalism communication tsjc established april 2002 predecessor communication studies department chinese language literature establishment coincides development media increasingly influencing world affairs time fast-growing globalization school research fields include international communication film television studies new media studies media operation management business journalism based comprehensive academic research journalism communication theories objective school bring full advantage tsinghua university comprehensive academic structure chinese international media construct first-rate discipline journalism communication studies cultivate talented professionals field explore advanced concepts journalism communication school also offers two-year graduate program international business journalism sponsored bloomberg l.p. international center journalists icfj trains talented students media professionals around globe financial media corporate communication school five research-oriented centers organize conduct academic research activities center international communications studies center new media studies center film television studies center media management studies center cultural industry studies legal studies tsinghua university dated back tsinghua college era 1911-1929 many students sent universities western countries legal studies graduating institutions columbia yale harvard tsinghua alumni played important role areas law diplomacy famous legal scholars tuan-sheng ch'ien yan shutang 燕树棠 wang huacheng 王化成 kung chuan hsiao 萧公权 pu xuefeng 浦薛凤 mei ju'ao 梅汝璈 xiang zhejun 向哲浚 diplomat tang yueliang 唐悦良 graduates tsinghua college went study abroad passing exams tsinghua college tsinghua university school law established 1929 tsinghua college renamed tsinghua university legal education tsinghua university time focused international affairs chinese legal studies courses political science economics could also found students curriculum japanese army invaded beijing 1937 school law developed greatly many chinese legal scholars graduated era including wang tieya 王铁崖 gong xiangrui 龚祥瑞 lou bangyan 楼邦彦 1952 response government policy turning tsinghua university engineering-focused university law school dismissed faculty appointed universities including peking university peking college political science law predecessor china university political science law 1995 formal school law tsinghua university yet courses law still taught tsinghua university september 8 1995 tsinghua university department law formally re-established april 25 1999 88th anniversary tsinghua university university formally changed department school law new law school inherited spirit old law school endeavored add international factors students curriculum due outstanding faculty members students tsinghua university school law risen become one leading law schools china since 2012 consistently ranked best second-best law school mainland china qs world university rankings graduate school shenzhen jointly founded tsinghua university shenzhen municipal government school directly affiliated tsinghua university beijing campus located university town shenzhen since 18 october 2003 graduate school shenzhen tsinghua university jointly founded tsinghua university shenzhen municipal government cultivating top level professionals carrying scientific technological innovations academic divisions tsinghua university 110 student associations covering five domains science technology physical training humanities arts public welfare name students association global affairs saga student association educational poverty alleviation saepa students performing arts club zijing volunteer service rural international student exchange rise students association science technology photography association foreign languages association association student international communication asic etc international students encouraged participate various extracurricular activities join student associations university fsao also organizes extracurricular activities international students including welcome party new students new year ’ party graduation party visits chinese cultural historical destinations sports competitions etc campus tsinghua university located northwest beijing haidian district designated universities academic institutes located former site qing dynasty royal gardens retains chinese-style landscaping well traditional buildings many buildings also western-style reflecting american influence history along rival neighbor peking university known throughout china wider world one beautiful campuses tsinghua university campus named one beautiful college campuses world panel architects campus designers forbes 2010 university asia list t. chuang 1914 graduate university illinois urbana–champaign helped design campus grounds tsinghua university influences american architectural style architectures university institute nuclear new energy technology separate campus northern suburb beijing tsinghua history museum covers construction area 5,060 m² collection old documents pictures artworks maps graphics videos music tells visitors history tsinghua university exhibition also pays tribute people contributed prestige development institution tsinghua university produced many notable graduates especially political sphere academic field industry tsinghua graduates political prominence disproportionately greater number graduates famous universities include former general secretary president hu jintao current party general secretary xi jinping former chairman national people congress wu bangguo former premier zhu rongji former first vice premier huang ju tsinghua also two nobel prize winners tsung-dao lee yang chen ning latter currently residing tsinghua campus term qinghua clique refers group communist chinese politicians graduated tsinghua university members fourth generation chinese leadership purported hold reformist hesitantly pro-democratic ideas number studied united states following graduation tsinghua said influenced reform ideals hu yaobang prc ascendance power began 2008 17th national congress cpc
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Computer architecture
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network encryption cracking network encryption cracking breaching network encryptions e.g. wep wpa ... usually use special encryption cracking software may done range attacks active passive including injecting traffic decrypting traffic dictionary-based attacks mentioned several types attacks possible precisely injecting traffic means inserting forged encrypted messages network may done either key known generate new messages key known encrypted message plaintext message gathered comparison two programs able latter aireplay wepwedgie decryption often requires 2 tools 1 gathering packets another analysing packet determining key gathering packets may done tools wireshark prismdump cracking may done tools wepcrack airsnort aircrack weplab gathering packets often great amount required perform cracking depending attack used 5-16 million frames may required attack command however surprisingly simple commands inputted wepcrack perl \progra~1\wepcrack\pcap-getiv.pl command generates log-file ivfile.log captured packet obtained wireshark prismdump packet least 5 million frames required perl \progra~1\wepcrack\wepcrack\.pl ivfile.log command asks wepcrack determine key log file aircrack another program even simpler use command need entered instead user asked type parameters click buttons first airodump started gather packets herefore channel mac-filter asked yet user need know per se instead 0 p may inputted respectively aircrack started file created airodump accessed 0 needs entered program determines key airsnort even simpler program completely interface-based attack simple brute-force attack however cracking encryption take several days weeks especially traffic low 4 users network cracking take least 2 weeks comparison tools noted may found security focus
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Computer security
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cracking wireless networks cracking wireless network defeating security wireless local-area network back-jack wireless lan commonly used wireless lan wi-fi network wireless lans inherent security weaknesses wired networks exempt wireless cracking information network attack similar direct intrusion two frequent types vulnerabilities wireless lans caused poor configuration caused weak flawed security protocols 802.11 networks use data frames management frames control frames data frames convey real data similar ethernet management frames maintain network configuration connectivity control frames manage access ether prevent access points clients interfering ether information management frames helpful better understand programs reconnaissance wardriving common method wireless network reconnaissance well-equipped wardriver uses laptop computer wireless card antenna mounted car power inverter connected gps receiver way connect internet wirelessly purpose wardriving locate wireless network collect information configuration associated clients laptop computer wireless card must support mode called monitor rfmon netstumbler network discovery program windows free netstumbler become one popular programs wardriving wireless reconnaissance although disadvantage detected easily wireless intrusion detection systems actively probes network collect information netstumbler integrated support gps unit support netstumbler displays gps coordinate information next information discovered network useful finding specific networks sorted collected data latest release netstumbler 1 april 2004 work well 64-bit windows xp windows vista inssider wi-fi network scanner 32-bit 64-bit versions windows xp vista 7 windows 8 android free open source software uses current wireless card wireless usb adapter supports gps devices namely use nmea 2.3 higher graphical user interface shows mac address ssid signal strength hardware brand security network type nearby wi-fi networks also track strength signals show time graph kismet wireless network traffic analyser os x linux openbsd netbsd freebsd wireshark packet sniffer network traffic analyser run popular operating systems support capture wireless traffic limited free open source decoding analysing wireless traffic foremost function wireshark give results obtained programs wireshark requires sufficient knowledge network protocols obtain full analysis traffic however airmagnet laptop analyser airmagnet handheld analyser wireless network analysis tools made airmagnet company started handheld analyser suitable surveying sites wireless networks deployed well finding rogue access points laptop analyser released hand-held product impractical reconnaissance wide areas commercial analysers probably offer best combination powerful analysis simple user interface however well adapted needs wardriver free programs androdumpper android apk used test hack wps wireless routers vulnerability using algorithms hack wifi network runs best android version 5.0+ airopeek packet sniffer network traffic analyser made wildpackets commercial program supports windows works wireless network interface cards become industrial standard capturing analysing wireless traffic however like wireshark airopeek requires thorough knowledge protocols use ability kismac program discovery wireless networks runs os x operating system functionality kismac includes gps support mapping ssid decloaking deauthentication attacks wep cracking two basic types vulnerabilities associated wlans caused poor configuration caused poor encryption poor configuration causes many vulnerabilities wireless networks often put use insufficient security settings security settings – default configuration – access obtained simply association without sufficient security settings networks easily defeated cloaking and/or mac address filtering poor encryption causes remaining vulnerabilities wired equivalent privacy wep defective defeated several ways wi-fi protected access wpa cisco lightweight extensible authentication protocol leap vulnerable dictionary attacks wep encryption standard firstly available wireless networks deployed 64 128 bit strength 64 bit wep secret key 40 bits initialisation vector 24 bits often called 40 bit wep 128 bit wep secret key 104 bits initialisation vector 24 bits called 104 bit wep association possible using password ascii key hexadr cracking wep fluhrer mantin shamir attack|fms attack chopping attack fms attack – named fluhrer mantin shamir – based weakness rc4 encryption algorithm researchers found 9000 possible 16 million initialisation vectors considered weak collecting enough allows determination encryption key crack wep key cases 5 million encrypted packets must captured collect 3000 weak initialisation vectors cases 1500 vectors cases 5000 needed success weak initialisation vectors supplied rc4 key-scheduling algorithm ksa |key scheduling algorithm ksa rc4 pseudo-random generation algorithm prga |pseudo random generator prng determine first byte wep key procedure repeated remaining bytes key chopping attack chops last byte captured encrypted packets breaks cyclic redundancy check checksum|integrity check value crc/icv 8 bits removed byte zero crc shortened packet made valid manipulation last four bytes manipulation result original xor certain value manipulated packet retransmitted method enables determination key collecting unique initialisation vectors main problem fms attack chopping attack capturing enough packets take weeks sometimes months fortunately speed capturing packets increased injecting packets network one address resolution protocol arp packets usually collected end transmitted access point repeatedly enough response packets captured arp packets good choice recognizable size 28 bytes waiting legitimate arp packet take awhile arp packets commonly transmitted authentication process rather waiting sending deauthentication frame pushes client network require client reauthenticate often creates arp packet wpa developed vulnerabilities wep wpa uses either pre-shared key wpa-psk used combination radius server wpa-radius encryption algorithm wpa uses either temporal key integrity protocol tkip advanced encryption standard aes wi-fi protected access wpa2|wpa2 developed vulnerabilities wpa-psk strengthen encryption wpa2 uses tkip aes requires encryption piece also authentication piece form extensible authentication protocol eap deployed piece wpa-psk attacked psk shorter 21 characters firstly four-way eap lan eapol handshaking|handshake must captured captured legitimate authentication reauthentication forced sending deauthentication packets clients secondly word word-list must cryptographic hash function|hashed hashed message authentication code – secure hash algorithm 1 two called nonce values along mac address client asked authentication mac address access point gave authentication word-lists found leap uses variation microsoft challenge handshake protocol version 2 ms-chapv2 handshake uses data encryption standard des key selection leap cracked dictionary attack attack involves capturing authentication sequence comparing last two bytes captured response generated word-list wpa-radius cracked however radius authentication server cracked whole network imperilled security authentication servers often neglected wpa2 attacked using wpa-psk attack largely ineffective aircrack-ng runs windows linux crack wep wpa-psk use pychkine-tews-weinmann korek attacks statistical methods efficient traditional fms attack aircrack-ng consists components airmon-ng configures wireless network card airodump-ng captures frames aireplay-ng generates traffic aircrack-ng cracking using data collected airodump-ng finally airdecap-ng decrypts packets captured thus aircrack-ng name suite also one components cowpatty automates dictionary attack wpa-psk runs linux program started using command-line interface specifying word-list contains passphrase dump file contains four-way eapol handshake ssid network void11 program deauthenticates clients runs linux mac address filtering used alone ineffective security measure combination encryption attack determining allowed mac address changing mac address attacker address etherchange one many programs available change mac address network adapters runs windows penetration test ing wireless network often stepping stone penetration testing internal network wireless network serves so-called entry vector wpa-radius use target site another entry vector must investigated 'wireless packet analyzer|sniffer find ip address es helpful network mapping access points usually connect nodes wireless network wired network bridge router bridge router use routing table forward packets finding relevant reachable ip addresses objective reconnaissance phase attacking organization internet relevant ip addresses determined collecting many domain name system|dns host names possible translating ip addresses ip address ranges called footprinting web search engine|search engine key finding much information possible target many cases organizations want protect resources internet access instance web server must accessible many organizations additionally message transfer agent|email servers file transfer protocol|ftp servers systems must accessible internet ip addresses organization often grouped together one ip address found rest probably found around name server store tables show domain names must translated ip addresses vice versa windows command nslookup|nslookup used query dns servers word help entered nslookup prompt list commands given linux command dig used query dns servers displays list options invoked option -h command host reverses ip addresses hostnames program nmap used reverse dns walker nmap -sl 1.1.1.1-30 gives reverse entries given range arin ripe apnic lacnic afrinic five regional internet registry|regional internet registries responsible assignment registration ip addresses website databases searched owner ip address registries respond search name organization list ip address ranges assigned name however records registries always correct cases useless probably computers access internet receive ip address dynamically dynamic host configuration protocol|dhcp protocol become popular last years decrease available ip addresses increase large networks dynamic dhcp particularly important many employees take portable computer one office another router/ firewall computing |firewall device people use home connect internet probably also functions dhcp server nowadays many router/dhcp devices perform network address translation nat nat device gateway telecommunications |gateway local network internet seen internet nat device seems single host nat local network use ip address space ip address ranges reserved private network s. ranges typically used local area network behind nat device 10.0.0.0 10.255.255.255 172.16.0.0 172.31.255.255 192.168.0.0 192.168.255.255 relevant ip addresses must narrowed reachable purpose process scanning enters scene access wireless network gained helpful determine network topology including names computers connected network nmap used available windows linux version however nmap provide user network diagram network scanner network view runs windows program asks one ip address ip address range program finished scanning displays map network using different pictures routers workstation server computing |servers laptop names added direct method finding hosts local area network|lan using program ping networking utility |ping using modern flavour unix shell computing |shell commands combined produce custom ping sweep|ping-sweeps using windows command-line also used create ping-sweep examples given reference ping-sweeps also known host scans nmap used host scan option -sp added nmap -n -sp 10.160.9.1-30 scans first 30 addresses subnet 10.160.9 -n option prevents reverse dns lookups ping packets could reliably determine whether computer line specified ip address nowadays internet control message protocol|icmp echo request packets sometimes blocked firewall operating system although nmap also probes tcp port 80 specifying tcp ports probe recommended pings blocked consequently nmap -sp -ps21,22,23,25,80,139,445,3389 10.160.9.1-30 achieve better results combining various options nmap -sp -ps21,22,23,25,80,135,139,445,1025,3389 -pu53,67,68,69,111,161,445,514 -pe -pp -pm 10.160.9.1-30 superb host scanning achieved nmap available windows unix operating systems offers graphical command-line interfaces purpose port scanning finding open ports computers found host scan port scan started network without making use results host scan much time wasted many ip addresses address range vacant programs communicate internet use either transmission control protocol|tcp user datagram protocol|udp protocol protocols support 65536 called port computer networking |ports programs choose bind allows programs run concurrently one ip address programs default ports often used example http servers commonly use tcp port 80 network scanners try connect tcp udp ports port accepts connection assumed commonly bound program running tcp connections begin syn packet sent client server server responds syn/ack packet finally client sends ack packet scanner sends syn packet gets syn/ack packet back port considered open rst packet received instead port considered closed response received port either considered filtered firewall running host ip address scanning udp ports difficult udp use handshakes programs tend discard udp packets process udp packet sent port program bound icmp error packet returned port considered closed answer received port considered either filtered firewall open many people abandoned udp scanning simple udp scanners distinguish filtered open ports although thorough scan 65536 ports would take time scanning common ports therefore nmap scans 1667 tcp ports default 2007 -p option instructs nmap scan specified ports nmap -p 21-25,80,100-160 10.150.9.46 specifying tcp udp ports also possible nmap -pt:21-25,80 u:5000-5500 10.150.9.46 nmap always requires specification host hosts scan single host specified ip address domain name multiple hosts specified ip address ranges examples 1.1.1.1 www.company.com 10.1.50.1-5,250-254 nmap performs tcp syn scan default scan packets syn flag set -ss option specifies default explicitly nmap started administrator privileges default scan takes effect nmap started user privileges connect scan performed -st option instructs nmap establish full connection scan inferior previous additional packet must sent logging target likely connect scan performed nmap executed user privileges ipv6 addresses scanned -sn option instructs nmap send packets none syn rst ack flags set tcp port closed rst packet sent return tcp port open filtered response null scan often bypass stateless firewall useful stateful firewall employed -su option instructs nmap send udp packets data icmp error returned port assumed closed response received port assumed open filtered differentiation open filtered ports severe limitation -su -sv options instruct nmap use application data application identification combination options lead slow scanning packets sent network faster cope dropped leads inaccurate scanning results intrusion detection system intrusion prevention system present target network detection becomes likely speed increases many intrusion prevention system|ips devices firewalls respond storm syn packets enabling syn cookies make appear every port open full speed scans even wreak havoc stateful firewall|stateful network devices nmap provides five templates adjusting speed also adapts -t0 option makes wait 5 minutes next packet sent -t1 option makes wait 15 seconds -t2 inserts 0.4 seconds -t3 default leaves timing settings unchanged -t4 reduces time-outs retransmissions speed things slightly -t5 reduces time-outs retransmissions even speed things significantly modern ids/ips devices detect scans use -t1 option user also define new template settings use instead provided one -sv option instructs nmap also determine version running application -o option instructs nmap try determine operating systems targets specially crafted packets sent open closed ports responses compared database -ox filename option instructs nmap save output file xml format vulnerability bug application program affects security made public places bugtraq|bugtraq full-disclosure mailing lists computer emergency response team|computer emergency response team cert brings statistical report every year 8064 vulnerabilities counted 2006 alone vulnerability scanning determining whether known vulnerabilities present target exploit computer security |exploit takes advantage software bug|bug application software|application take effect execution arbitrary commands inserting execution path program privilege escalation|escalation privileges bypass authentication infringement confidentiality result metasploit project|metasploit framework released 2003 framework provided first time basic procedure using metasploit choose exploit choose payload set ip address port target start exploit evaluate stop repeat procedure metasploit suited finding vulnerabilities host vulnerability scanner alternatively port scanner found open port exploits port may tried metasploit 3.0 provides following payloads vnc connections need relatively large bandwidth computing |bandwidth usable someone front compromised computer interaction seen quickly command-line interfaces linux os x powerful windows meterpreter payload remedies shortcomings reference gives list meterpreter commands ultimate gratification network intruder always obtain administrator privileges network intruder inside one first undertakings often install so-called rootkit target computer collection programs facilitate durable influence system programs used compromise new user computing user account|user accounts new computers network programs obscure presence intruder obscuring programs may include false versions standard network utilities netstat programs remove data log files computer relate intruder yet programs rootkit may used survey network overhear passwords travelling rootkits may also give means change operating system computer installed network intruder proceeds creating one called backdoor computing |back doors access provisions hard find system administrators serve prevent logging monitoring results normal use network back door may concealed account account privileges escalated may utility remote access telnet configured operate port number customary network intruder proceeds stealing files stealing credit card information preparing computer send spam emails another goal prepare next intrusion cautious intruder protective discovery location method choice use computer already attacked intermediary intruders use series intermediate computers making impracticable locate purpose back door maintain communication channel methods control host gained entry methods include file transfer execution programs often important make sure access communication remains secret access control desirable order prevent others using back door back orifice 2000 designed back door server runs windows client computing |clients windows linux operating systems server configured easily utility configuration server needs uploaded target started back orifice 2000 supports file transfer file execution keystroke logging|logging keystrokes control connections also aes plug-in computing |plug-in traffic encryption stcpio plug-in obfuscation traffic first plug-in adds security combination plug-ins makes much harder ids relate traffic back door information found http //www.bo2k.com rootkits specialize hiding programs hacker defender hxdef open source rootkit windows hide files process windows registry|registry entries port multiple dynamic-link library|dlls although simple command-line interface back door often better use ability hide appropriate tool unprotected wireless network extremely insecure anywhere within broadcast range someone eavesdrop start using network therefore ieee 802.11 standard wireless networks accompanied wired equivalent privacy wep security protocol takes care following wep criticized security experts experts regard ineffective 2004 draft better security protocol appeared included ieee 802.11 standard 2007 new protocol ieee 802.11i-2004|wpa2 uses aes block cipher instead rc4 algorithm better procedures authentication key distribution wpa2 much secure wep wep still wide use 2009 many wireless routers also support controlling mac addresses computers authorized use wireless network measure effectively stop neighbour using network experienced intruders stopped mac filtering attacked mac address faked easily past turning broadcasting ssid also thought give security wireless network case however freely available tools exist quickly discover ssid broadcast microsoft also determined switching broadcasting ssid leads less security details found non-broadcast wireless networks microsoft windows returning encryption wep specification encryption strength unable withstand determined hacking therefore wi-fi protected access wpa derived wep software upgrades often available latest devices conform ieee 802.11g-2003|802.11g ieee 802.11n-2009|802.11n standards also support wpa2 wpa uses tkip encryption wpa2 uses stronger aes method recommended use hardware supports wpa wpa2 installing updates regularly disabling wps setting custom ssid requiring wpa2 using strong password make wireless router difficult crack even unpatched security flaws router software firmware may still used attacker bypass encryption gain control device many router manufacturers always provide security updates timely manner especially inexpensive models wps currently severe vulnerability 8 pin numbered 0-9 passwords used easily split two halves means half brute-forced individually possible combinations greatly lessened 10^4 10^4 opposed 10^8 vulnerability addressed manufacturers days using lock mechanism router automatically lock wps number failed pin attempts take number hours router automatically unlock even rebooted make wps attacks completely obsolete without lock feature wpa2 router wps enabled easily cracked 5 hours using brute force wps attack ssid used routers identify within mass 2.4 3.6 5 60 ghz frequencies currently flying around cities also used seed router password hashes standard popular ssid netgear brute forced use rainbow table however use salt greatly improves security rainbow tables popular method wpa wpa2 cracking obtaining known 4 way handshake device connecting network 4-stage authorization process referred 4 way handshake wireless device undergoes process handshake sent air easily monitored saved external system handshake encrypted router password means opposed communicating router directly quite slow cracker attempt brute force handshake using dictionary attacks device connected directly router still undergo process however handshake sent connected wire opposed air intercepted 4 way handshake already intercepted mean cracker granted immediate access however password used contains least 12 characters consisting random upper lower case letters numbers spell word name pattern password essentially uncrackable give example let take minimum 8 characters wpa2 suppose take upper case lower case letters digits 0-9 small selection symbols avail hefty choice 64 characters 8 character length password grand total 64^8 possible combinations taking single machine could attempt 500 passwords per second gives us 17,900 years attempt every possible combination even mention amount space necessary store combination dictionary note use mac filtering protect network work macs using network easily detected spoofed network scanner sniffer application program makes use wireless network interface card repeatedly tunes wireless card successively number radio channels network detector passive scanning|passive scanner pertains receiver wireless card therefore scanning detected attacker obtain considerable amount information passive scanner information may obtained sending crafted frames provoke useful responses called active scanning probing active scanning also involves use transmitter wireless card activity therefore detected wireless card located detection possible intrusion detection system wireless networks locating possible suitable equipment wireless intrusion detection systems designed detect anomalous behaviour one sensors collect ssids radio channels beacon intervals encryption mac addresses transmission speeds signal-to-noise ratio s. wireless intrusion detection systems maintain registry mac addresses unknown clients detected making use someone else wireless access point wireless router connect internet – without owner consent way – punishable criminal law netherlands true even device uses form access protection penetrate someone else computer without owner consent punishable criminal law though consensus computer attackers divided following groups term hacker originally used someone could modify computer purposes hacking intrusion combined direct alteration security data structures breached system word hacking often confused cracking popular media discourse obfuscates fact hacking less eavesdropping related interference alteration however consistent abuse news media 2007 term hacker commonly used someone accesses network computer without authorization owner 2011 collins english dictionary|collins dictionary stated word hacker mean computer fanatic particular one means personal computer breaks computer system company government like also denoted sense word hacker slang slang words appropriate formal writing speech computer experts reserve word hacker clever programmer call someone breaks computers intruder attacker cracker category computer network security category computer security category cryptographic attacks category data security category dutch law category hacking computer security category local area networks category wi-fi category wireless networking
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Computer security
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server routing protocol server routing protocol srp proprietary network protocol used transfer data blackberry enterprise server research motion blackberry infrastructure srp communication takes place tcp port 3101 default srp work two different part 1 srp id 2 srp authorization key blackberry enterprise server installation unique server routing protocol identifier srp id srp authentication key must entered srp id srp authentication key register authenticate blackberry enterprise server network work flow like authentication process srp id thought login name authentication key password srp id uniquely identifies blackberry enterprise server network blackberry enterprise server connects blackberry infrastructure must provide two pieces information connect open session blackberry enterprise server connected blackberry infrastructure another server attempts connect using srp id authentication key blackberry infrastructure drops connection blackberry enterprise server creates session newly connecting server multiple concurrent connections made srp id blackberry device attempts send message must include srp id blackberry enterprise server note service book menu blackberry device open desktop cmime service book specified unique identifier uid value srp id blackberry enterprise server blackberry device attempts send messages blackberry device sends message arrives blackberry infrastructure message contains srp id pulled service book uid value blackberry infrastructure uses information send message corresponding blackberry enterprise server decryption processing ref blackberry server trial mentioning technology
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Internet protocols
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computer file computer file computer resource recording data discretely computer storage device words written paper information written computer file files edited transferred internet particular computer system different types computer files designed different purposes file may designed store picture written message video computer program wide variety kinds data types files store several types information using computer programs person open read change save close computer file computer files may reopened modified copied arbitrary number times typically files organised file system keeps track files located disk enables user access word file derives latin filum thread file used context computer storage early january 1940 punched card methods scientific computation w.j eckert stated first extensive use early hollerith tabulator astronomy made comrie used building table successive differences adding large numbers harmonic terms tables functions constructed differences great efficiency either printed tables file punched cards february 1950 radio corporation america rca advertisement popular science magazine describing new memory vacuum tube developed rca stated results countless computations kept 'on file taken 'file exists 'memory tube developed rca laboratories electronically retains figures fed calculating machines holds storage memorizes new ones speeds intelligent solutions mazes mathematics 1952 file denoted inter alia information stored punched cards early use underlying hardware rather contents stored denominated file example ibm 350 disk drives denominated disk files introduction circa 1961 burroughs mcp mit compatible time-sharing system concept file system managed several virtual files one storage device origin contemporary denotation word although contemporary register file demonstrates early concept files use greatly decreased modern operating systems files organized one-dimensional arrays bytes format file defined content since file solely container data although platforms format usually indicated filename extension specifying rules bytes must organized interpreted meaningfully example bytes plain text file windows associated either ascii utf-8 characters bytes image video audio files interpreted otherwise file types also allocate bytes metadata allows file carry basic information file systems store arbitrary interpreted file system file-specific data outside file format linked file example extended attributes forks file systems done via sidecar files software-specific databases methods however susceptible loss metadata container archive file formats instant time file might size normally expressed number bytes indicates much storage associated file modern operating systems size non-negative whole number bytes system limit many older operating systems kept track number blocks tracks occupied file physical storage device systems software employed methods track exact byte count e.g. cp/m used special control character ctrl-z signal end text files general definition file require size real meaning however unless data within file happens correspond data within pool persistent storage special case zero byte file files newly created files yet data written may serve kind flag file system accidents results aborted disk operations example file link points typical unix-like system probably defined size seldom changes compare also file size may obscure information computer file consist smaller packets information often called records lines individually different share common traits example payroll file might contain information concerning employees company payroll details record payroll file concerns one employee records common trait related payroll—this similar placing payroll information specific filing cabinet office computer text file may contain lines text corresponding printed lines piece paper alternatively file may contain arbitrary binary image blob may contain executable way information grouped file entirely designed led plethora less standardized file structures imaginable purposes simplest complex computer files used computer programs create modify delete files use as-needed basis programmers create programs decide files needed used often names cases computer programs manipulate files made visible computer user example word-processing program user manipulates document files user personally names although content document file arranged format word-processing program understands user able choose name location file provide bulk information words text stored file many applications pack data files single file called archive file using internal markers discern different types information contained within benefits archive file lower number files easier transfer reduce storage usage organize outdated files archive file must often unpacked next using basic operations programs perform file files computer created moved modified grown shrunk deleted cases computer programs executed computer handle operations user computer also manipulate files necessary instance microsoft word files normally created modified microsoft word program response user commands user also move rename delete files directly using file manager program windows explorer windows computers command lines cli unix-like systems user space programs operate directly low level file kernel deals files handles user-space interaction files manner transparent user-space programs operating system provides level abstraction means interaction file user-space simply filename instead file descriptor example rm filename delete file link file many links file removed kernel considers file memory space free reallocated free space commonly considered security risk due existence file recovery software secure-deletion program uses kernel-space system functions wipe file data modern computer systems files typically accessed using names filenames operating systems name associated file others file anonymous pointed links names latter case user identify name link file false analogue especially exists one link file files links files located directories however generally directory contain either list files list links files within definition paramount importance term file includes directories permits existence directory hierarchies i.e. directories containing sub-directories name refers file within directory must typically unique words must identical names within directory however operating systems name may include specification type means directory contain identical name one type object directory file environments file named file name path file directory must uniquely identify among files computer system—no two files name path file anonymous named references exist within namespace cases name within namespace refer exactly zero one file however file may represented within namespace zero one names string characters may well-formed name file link depending upon context application whether name well-formed depends type computer system used early computers permitted letters digits name file modern computers allow long names 255 characters containing almost combination unicode letters unicode digits making easier understand purpose file glance computer systems allow file names contain spaces others case-sensitivity file names determined file system unix file systems usually case sensitive allow user-level applications create files whose names differ case characters microsoft windows supports multiple file systems different policies regarding case-sensitivity common fat file system multiple files whose names differ case user uses disk editor edit file names directory entries user applications however usually allow user create multiple files name differing case computers organize files hierarchies using folders directories catalogs concept irrespective terminology used folder contain arbitrary number files also contain folders folders referred subfolders subfolders contain still files folders thus building tree-like structure one master folder root folder — name varies one operating system another contain number levels folders files folders named files except root folder often name use folders makes easier organize files logical way computer allows use folders file folder name also path identifies folder folders file folder resides path sort special character—such slash—is used separate file folder names example illustration shown article path uniquely identifies file called folder called turn contained folder called folder file names separated slashes example topmost root folder name path begins slash root folder name would precede first slash many computer systems use extensions file names help identify contain also known file type windows computers extensions consist dot period end file name followed letters identify type file extension identifies text file extension identifies type document documentation commonly microsoft word file format even extensions used computer system degree computer system recognizes heeds vary systems required systems completely ignored presented many modern computer systems provide methods protecting files accidental deliberate damage computers allow multiple users implement file permissions control may may modify delete create files folders example given user may granted permission read file folder modify delete user may given permission read modify files folders execute permissions may also used allow certain users see contents file folder permissions protect unauthorized tampering destruction information files keep private information confidential unauthorized users another protection mechanism implemented many computers read-only flag flag turned file accomplished computer program human user file examined modified flag useful critical information must modified erased special files used internal parts computer system systems also include hidden flag make certain files invisible flag used computer system hide essential system files users alter file useful purpose must physical manifestation file abstract concept real computer system must real physical analogue exist physical terms computer files stored type data storage device example operating systems store files hard disk hard disks ubiquitous form non-volatile storage since early 1960s files contain temporary information may stored ram computer files also stored media cases magnetic tapes compact discs digital versatile discs zip drives usb flash drives etc use solid state drives also beginning rival hard disk drive unix-like operating systems many files associated physical storage device examples files directories virtual files exist objects within operating system kernel seen running user program files usually represented either file control block file handle file control block fcb area memory manipulated establish filename etc passed operating system parameter used older ibm operating systems early pc operating systems including cp/m early versions ms-dos file handle generally either opaque data type integer introduced around 1961 algol-based burroughs mcp running burroughs b5000 ubiquitous file said corrupted contents saved computer way ca n't properly read either human software depending extension damage original file sometimes recovered least partially understood file may created corrupt may corrupted later point overwriting many ways file become corrupted commonly issue happens process writing file disk example image-editing program unexpectedly crashes saving image file may corrupted program could n't save entirety program might warn user error allowing another attempt saving file examples reasons files become corrupted include although file corruption usually happens accidentally may also done purpose fool someone else thinking assignment ready earlier date potentially gaining time finish said assignment services provide demand file corruption essentially fill given file random data ca n't opened read yet still seems legitimate one effective countermeasures file corruption backing important files event important file becoming corrupted user simply replace backed version computer files contain information extremely important back-up process used protect disasters might destroy files backing files simply means making copies files separate location restored something happens computer deleted accidentally many ways back files computer systems provide utility programs assist back-up process become time-consuming many files safeguard files often copied removable media writable cds cartridge tapes copying files another hard disk computer protects failure one disk necessary protect failure destruction entire computer copies files must made media taken away computer stored safe distant location grandfather-father-son backup method automatically makes three back-ups grandfather file oldest copy file son current copy way computer organizes names stores manipulates files globally referred file system computers least one file system computers allow use several different file systems instance newer ms windows computers older fat-type file systems ms-dos old versions windows supported addition ntfs file system normal file system recent versions windows system advantages disadvantages standard fat allows eight-character file names plus three-character extension spaces example whereas ntfs allows much longer names contain spaces call file ntfs fat would restricted something like unless using vfat fat extension allowing long file names file manager programs utility programs allow users manipulate files directly allow move create delete rename files folders although actually allow read contents file store information every computer system provides least one file-manager program native file system example file explorer formerly windows explorer commonly used microsoft windows operating systems nautilus common several distributions linux
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Computer file systems
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appfolio appfolio founded 2006 offers software-as-a-service saas applications vertical markets appfolio initially focused property management software acquisition mycase 2012 expanded law practice management industry company ’ headquarters goleta california united states also offices san diego california dallas texas appfolio established 2006 co-founders klaus schauser jon walker schauser previously founded expertcity company ’ first focus property management small-to-medium businesses first product appfolio property manager launched 2007 november 2012 appfolio acquired mycase legal practice management software provider appfolio purchased real estate software firm rentlinx april 2015 acquisition included rights website showmetherent.com expanded sphere appfolio ’ clients provided greater listing presence may 2015 appfolio announced ipo unveiled june raised 74 million 2019 appfolio acquired dynasty marketplace inc. leading provider advanced artificial intelligence ai solutions real estate market 2019 2018 2017 2016 2015 2014
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Distributed computing architecture
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aliens computer game 1987 video game aliens computer game also known aliens video game developed software studios published electric dreams software 1987 initially amstrad cpc commodore 64 zx spectrum based film title ports commodore 16 msx developed mr. micro published 1987 aliens computer game played first-person perspective set inside atmosphere processing plant maze complex consisting 255 rooms player encounters alien enemies throughout game upon killing alien body leaves deadly pool acid blood must avoided player also faces threat bio-mechanical growth left uncontained results new alien eggs facehugger enemies player ultimate goal reach room houses queen alien nests must destroyed player directly control team marine soldiers issue orders team mobile tactical operations bay mtob playing mtob player view team surroundings via video cameras attached soldier helmet according retro gamer game praised computing press zzap amstrad action sinclair user awarded 81 90 5/5 respectively crash gave score 84 one reviewer declaring best game-of-the-film date review zzap 64 also opined best tie-in game date good game boot computer gamer gave excellent game superb film overall score 80 commodore user gave 8 10 sinclair gave 9 10 1993 commodore force ranked game number 59 list top 100 commodore 64 games retro gamer retrospective darren jones opined despite incredible basic look aliens dripped atmosphere quite unlike movie conversion time bloody good first-person view used game perfectly matched moment film pumped-up marines start exploring deserted base game progressed managed capture terror confusion movie way titles managed magazine also declared scariest 8-bit game ever made stephen kleckner gamesbeat wrote may lack audio/visual punch gameplay tightly defined forward-thinking time also recommended windows fan remake aliens titled lv-426
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Computer architecture
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computer architecture simulator computer architecture simulator program simulates execution computer architecture computer architecture simulators used following purposes computer architecture simulators classified many different categories depending context full-system simulator execution-driven architecture simulation level detail complete software stacks real systems run simulator without modification full system simulator provides virtual hardware independent nature host computer full-system model typically includes processor cores peripheral devices memories interconnection buses network connections emulators full system simulators imitate obsolete hardware instead development hardware defining property full-system simulation compared instruction set simulator model allows real device drivers operating systems run single programs thus full-system simulation makes possible simulate individual computers networked computer nodes software network device drivers operating systems network stacks middleware servers application programs full system simulation speed system development process making easier detect recreate repair flaws use multi-core processors driving need full system simulation extremely difficult time-consuming recreate debug errors without controlled environment provided virtual hardware also allows software development take place hardware ready thus helping validate design decisions cycle-accurate simulator computer program simulates microarchitecture cycle-by-cycle basis contrast instruction set simulator simulates instruction set architecture usually faster cycle-accurate specific implementation architecture often used emulating older hardware time precisions important legacy reasons often cycle-accurate simulator used designing new microprocessorsthey tested benchmarked accurately including running full operating system compilers without actually building physical chip easily change design many times meet expected plan cycle-accurate simulators must ensure operations executed proper virtual real possible timebranch prediction cache misses fetches pipeline stalls thread context switching many subtle aspects microprocessors
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Computer architecture
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time gal time gal interactive movie video game developed published taito malone films originally released japan arcades 1985 action game uses full motion video fmv display on-screen action player must correctly choose on-screen character actions progress story pre-recorded animation game produced toei animation game set fictional future time travel possible protagonist reika travels different time periods search criminal luda time successfully tracking luda reika prevents plans alter past time gal inspired success earlier laserdisc video games notably 1983 title dragon lair also used pre-recorded animation game later ported sega cd worldwide release also laseractive japan home console versions received mixed reception time gal fmv-based game uses pre-recorded animation rather sprites display on-screen action gameplay divided levels referred time periods game begins 4001 ad theft time travel device thief luda steals device take world changing history reika protagonist also known time gal uses time travel device pursue travels different time periods 70,000,000 bc 44 bc 1588 ad 2010 ad search luda time period scenario presents series threats must avoided confronted successfully navigating sequences allows player progress another period player uses joystick button input commands though home versions use game controller directional pad game progresses visual cues—highlighted portions background foreground—will appear screen help survive dangers occur throughout stage difficult settings omit visual cues depending location cue player input one four directions left right attack shoot target laser gun inputting correct command either avoid neutralize threats progress game incorrect choices result character death reika dying many times results game specific moments game involve reika stopping time moments players presented list three options seven seconds choose one save character game uses laserdisc technology stream pre-recorded animation produced japanese studio toei animation game features raster graphics crt monitor amplified monaural sound reika physical appearance possibly derived either lum urusei yatsura yuri dirty pair several factors prevented overseas release decline popularity laserdisc arcade games mid-80s expensive price laserdisc technology difficulty translate original japanese release reika voiced yuriko yamamoto since original release arcades japan 1985 time gal ported different home formats first released exclusively japan nippon victor video high density format could played microsoft msx via sony laserdisc player release sega cd console 1991 spawned numerous games took advantage cd technology introduce interactive fmvs among new titles time gal one several older laserdisc-based games ported system renovation products acquired rights publish time gal sega cd wolf team handling development released along similar games part action-reaction series first released japan november 1992 north america europe next year macintosh version also released japan 1994 american press coverage japanese release prompted video game enthusiasts contact renovations western release number requests persuaded renovation president hide irie announce release usa addition dubbed english death scenes us version censored sega cd version uses smaller color palette original includes video gallery requires passwords view level animation sequences features new opening ending theme shinji tamura motoi sakuraba respectively time gal ported playstation 1996 compilation ninja hayate another laserdisc arcade game developed taito release lacks sega cd version additional content features accurate reproduction animation compilation also released sega saturn following year game also played pioneer laseractive via sega mega-ld module laseractive version rarest home release time gal well one expensive system among collectors april 1 2017 taito classics announced would release several older games onto mobile devices time gal first release game later released japan april 5 2017 ability use game navigational function ability see game original concept art acquired in-app purchases gamepro magazine noted japanese players ate first released japanese arcades however gamesetwatch todd ciolek believed released late life laserdisc games players getting tired genre gameplay commented despite gameplay unique charming gamepro reviewer referred arcade game lost laserdisc treasure enthusiastic sega cd release called death sequences hilarious felt reduced tediousness dying mega magazine rated sega cd version number five cd game commenting though lacked difficulty good showcase system prior sega cd release electronic gaming monthly praised use cd technology felt would followed titles similar gameplay critics praised time gal visuals gamefan magazine praising wolfteam port game complimented sega cd version graphics short load times gamepro said animation great bright vivid colors fast-paced exciting movement praised funny gameplay nonstop action chris bieniek videogames computer entertainment criticized story nonsensical said unlockable video gallery nice feature effectively eliminates replay value compounds easiness game give low longevity nonetheless recommended time gal based chiefly gameplay though never really feel like 're control time gal movements zany action undeniable appeal takes lot slack shawn sackenheim allgame complimented animation calling high quality criticized sega cd graphics calling downgraded commented though time gal offered good thrill lacked replay value ciolek echoed similar statements saying enjoyable watch play commented game frustrating rigid compared contemporary standards electronic gaming monthly group reviewers praised sega cd version graphics quality three four reviewers lauded gameplay specifically challenge format reviewer stated n't care type game referring gameplay nothing memorizing author masaru takeuchi attributes origin quick time event game mechanic laserdisc games like dragon lair time gal ign levi buchanan listed fmv games like time gal one reasons behind sega cd commercial failure citing waste system capabilities ciolek referred protagonist one first human heroines industry added reika appealing lead character taito could easily turned mascot featured games media character later included alfa system shooting game castle shikigami iii —taito published arcade version japan game reika features similar attacks personality character visual design updated reika recent appearance elevator action remake elevator action deluxe one free taito dlcs
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Computer architecture
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xry software xry digital forensics mobile device forensics product swedish company micro systemation used analyze recover information mobile devices mobile phones smartphones gps navigation tools tablet computers consists hardware device connect phones pc software extract data xry designed recover contents device forensic manner contents data relied upon user typically used civil/criminal investigations intelligence operations data compliance electronic discovery cases software available law enforcement military intelligence agencies become well known digital forensics community one common tools type work many complex challenges examining mobile phones comparison forensic examination normal computers many mobile phones proprietary operating systems makes reverse engineering devices complex operation speed mobile device market also means many new devices manufactured regular basis mobile forensics tool must deal issues suitable task xry system allows logical examinations direct communication device operating system also physical examinations bypassing operating system dumping available memory whilst logical recovery data generally better supported devices physical examination offers ability recover deleted information sms text messages images call records etc complexities topic specialist training usually recommended operate software latest versions include support recover data smartphone apps android iphone blackberry devices data recovered xry used successfully various court systems around world xry tested number different government organizations suitable needs worldwide use
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Computer security
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art metaobject protocol art metaobject protocol amop 1991 book gregor kiczales jim des rivieres daniel g. bobrow three working xerox parc subject metaobject protocol book contains explanation metaobject protocol desirable de facto standard metaobject protocol supported many common lisp implementations extension common lisp object system clos complete portable implementation clos metaobject protocol defined book provided xerox parc portable common loops book presents simplified clos implementation common lisp called closette sake pedagogical brevity include complex exotic clos features forward-referencing superclasses full class method redefinitions advanced user-defined method combinations complete integration clos classes common lisp type system also lacks support compilation error checking since purpose closette actual use simply demonstrate fundamental power expressive flexibility metaobject protocols application principles metacircular evaluator 1997 talk oopsla alan kay called best book anybody written ten years contended contained profound insights practical insights oop dismayed written highly lisp-centric clos-specific fashion calling hard book people read n't know lisp culture hard read
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Programming language topics
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clock software clock mobile app included iphone since iphone os 1 ipad since ios 6 app world clock alarms stopwatch timer tabs ios 10 bedtime tab added world clock section allows user access temperature time pressure major cities choice user add new cities tapping plus icon top screen typing name city user wants add user also remove cities swiping left clicking delete button alarms section allows user view alarms week view create new alarms turn existing alarms stopwatch section allows user ability time events see long take app also allows user pause reset use stopwatch lap feature timer section allows user set timer count specific time timer reaches zero alarm sounded ios 10 later versions bedtime feature allows user get better sleep done determining user would like wake many days alarm go many hours sleep user would like whether user would want bedtime notification feature also integrates health application track sleep data since ios 7 app icon shows user current time since ios 10 interface dark theme new stopwatch face accessed swiping left
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Operating systems
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natural-language generation natural-language generation nlg software process transforms structured data natural language used produce long form content organizations automate custom reports well produce custom content web mobile application also used generate short blurbs text interactive conversations chatbot might even read loud text-to-speech system automated nlg compared process humans use turn ideas writing speech psycholinguists prefer term language production process also described mathematical terms modeled computer psychological research nlg systems also compared translators artificial computer languages decompilers transpilers also produce human-readable code generated intermediate representation human languages tend considerably complex allow much ambiguity variety expression programming languages makes nlg challenging nlg may viewed opposite natural-language understanding whereas natural-language understanding system needs disambiguate input sentence produce machine representation language nlg system needs make decisions put concept words practical considerations building nlu vs. nlg systems symmetrical nlu needs deal ambiguous erroneous user input whereas ideas system wants express nlg generally known precisely nlg needs choose specific self-consistent textual representation many potential representations whereas nlu generally tries produce single normalized representation idea expressed nlg existed long time commercial nlg technology recently become widely available nlg techniques range simple template-based systems like mail merge generates form letters systems complex understanding human grammar nlg also accomplished training statistical model using machine learning typically large corpus human-written texts pollen forecast scotland system simple example simple nlg system could essentially template system takes input six numbers give predicted pollen levels different parts scotland numbers system generates short textual summary pollen levels output example using historical data july 1 2005 software produces grass pollen levels friday increased moderate high levels yesterday values around 6 7 across parts country however northern areas pollen levels moderate values 4 contrast actual forecast written human meteorologist data pollen counts expected remain high level 6 scotland even level 7 south east relief northern isles far northeast mainland scotland medium levels pollen count comparing two illustrates choices nlg systems must make discussed process generate text simple keeping list canned text copied pasted possibly linked glue text results may satisfactory simple domains horoscope machines generators personalised business letters however sophisticated nlg system needs include stages planning merging information enable generation text looks natural become repetitive typical stages natural-language generation proposed dale reiter content determination deciding information mention text instance pollen example deciding whether explicitly mention pollen level 7 south east document structuring overall organisation information convey example deciding describe areas high pollen levels first instead areas low pollen levels aggregation merging similar sentences improve readability naturalness instance merging two following sentences following single sentence lexical choice putting words concepts example deciding whether medium moderate used describing pollen level 4 referring expression generation creating referring expressions identify objects regions example deciding use northern isles far northeast mainland scotland refer certain region scotland task also includes making decisions pronouns types anaphora realization creating actual text correct according rules syntax morphology orthography example using future tense alternative approach nlg use end-to-end machine learning build system without separate stages words build nlg system training machine learning algorithm often lstm large data set input data corresponding human-written output texts end-to-end approach perhaps successful image captioning automatically generating textual caption image popular media paid attention nlg systems generate jokes see computational humor commercial perspective successful nlg applications data-to-text systems generate textual summaries databases data sets systems usually perform data analysis well text generation research shown textual summaries effective graphs visuals decision support computer-generated texts superior reader perspective human-written texts first commercial data-to-text systems produced weather forecasts weather data earliest system deployed fog used environment canada generate weather forecasts french english early 1990s success fog triggered work research commercial recent applications include uk met office text-enhanced forecast currently considerable commercial interest using nlg summarise financial business data indeed gartner said nlg become standard feature 90 modern bi analytics platforms nlg also used commercially automated journalism chatbots generating product descriptions e-commerce sites summarising medical records enhancing accessibility example describing graphs data sets blind people example interactive use nlg wysiwym framework stands see meant allows users see manipulate continuously rendered view nlg output underlying formal language document nlg input thereby editing formal language without learning content generation systems assist human writers makes writing process efficient effective content generation tool based web mining using search engines apis built tool imitates cut-and-paste writing scenario writer forms content various search results relevance verification essential filter irrelevant search results based matching parse tree query parse trees candidate answers alternative approach high-level structure human-authored text used automatically build template new topic automatically written wikipedia article several companies started since 2009 build systems transform data narrative using nlg ai techniques include narrative science phrasetech arria nlg automated insights retresco visual nlg yseop united robots scientific fields nlg researchers need test well systems modules algorithms work called evaluation three basic techniques evaluating nlg systems ultimate goal useful nlg systems helping people first techniques however task-based evaluations time-consuming expensive difficult carry especially require subjects specialised expertise doctors hence areas nlp task-based evaluations exception norm recently researchers assessing well human-ratings metrics correlate predict task-based evaluations work conducted context generation challenges shared-task events initial results suggest human ratings much better metrics regard words human ratings usually predict task-effectiveness least degree although exceptions ratings produced metrics often predict task-effectiveness well results preliminary case human ratings popular evaluation technique nlg contrast machine translation metrics widely used
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Computational linguistics
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accelerator software accelerator collection development solutions ibm windows platforms using .net framework and/or lansa technologies provided surround technologies accelerator development architecture tool building windows web apps within structured framework intent accelerator solutions provide rapid application development rad environment produces well-designed n-tier code run client/server web mobile deployment use microsoft ’ .net framework recommended surround zero-lock development optimal deployment flexibility including windows presentation foundation wpf responsive web mobile design asp.net mvc bootstrap clients accelerator uses customizable templates standards naming conventions generate code generated code human readable standardized minimize testing debugging customization future maintenance efforts generated code follows object-oriented programming design principles inversion control ioc pattern observer pattern model–view–viewmodel mvvm oo techniques avoid redundancy promote ease testing maintenance supports asp.net mvc3 framework patterns followed architecture adapted depending case flexibility promoted typical use abstraction patterns practical abstraction promoted though use windows presentation foundation windows communication foundation accelerator core system architecture provides base set functionality wizard-driven code generation implementation accelerator architecture supports service-oriented architecture includes built-in features like business objects frameworks bus interfaces plug-ins xml dashboards wizards simplify deployment accelerator business objects services implements framework consists server-side business objects presentation data service buses service adapters service-oriented architecture integrates adapters xml soap rest activex .net xaml/wpf etc soa bos functions ibm windows lansa – virtually server
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Operating systems
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renjin renjin implementation r programming language atop java virtual machine free software released gpl renjin tightly integrated java allow embedding interpreter java application full two-way access java r code renjin development primarily supported bedatadriven ultimately made possible several current past contributors including mehmet hakan satman hannes mühleisen ruslan shevchenko renjin roots lie abortive 2010 attempt compile gnu r interpreter jvm via nestedvm toolchain involves cross-compiling c fortran code static mips binary nestedvm translate jvm bytecode proved challenging gnu r grown rely heavily dynamic linking best c standard library implementation available time mips architecture newlib fully compatible gnu c library gnu r developed experience r4jvm project provided bedatadriven team depth look gnu r codebase convinced new implementation written java feasible undertaking development renjin began october 2010 rapidly resulted functional minimal interpreter r language
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Programming language topics
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windows live onecare safety scanner windows live onecare safety scanner formerly windows live safety center codenamed vegas online scanning pc cleanup diagnosis service help remove viruses spyware/adware malware free web service part windows live november 18 2008 microsoft announced discontinuation windows live onecare offering users new free anti-malware suite microsoft security essentials available since second half 2009 however windows live onecare safety scanner branding windows live onecare discontinued time service officially discontinued april 15 2011 replaced microsoft safety scanner windows live onecare safety scanner offered free online scanning protection threats windows live onecare safety scanner must downloaded installed computer scan computer full service scan looks common pc health issues viruses temporary files open network ports searches removes viruses improves computer performance removes unnecessary clutter pc hard disk user choose full scan customized quick scan full scan scans viruses comprehensive scan quick scan hard disk performance disk fragmentation scan and/or desk cleanup scan network safety open port scan quick scan scans viruses specific areas computer quick scan faster full scan hence appellation service also provides virus database information online threats general computer security documentation tools virus scanner windows live onecare safety scanner site runs scan user computer site visited run periodic scans system provide features prevent viruses infecting computer time thereafter simply resolves detected infections many users posted product feedback forum report script errors relating internet explorer 7 besides ie browser supported service onecare safety scanner team actively solving problems many registry-related
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Computer security
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young sherlock legacy doyle young sherlock legacy doyle also referred young sherlock doyle isan japan-exclusive game msx developed pack-in-video released 1987 game based 1985 movie young sherlock holmes however plot completely different movie
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Computer architecture
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smartisan os smartisan os android-based smartphone platform developed chinese company smartisan custom rom smartphones potentially tablet devices first smartphone utilize smartisan os smartisan t1 ceo smartisan co. ltd. luo yonghao said sina weibo smartisan portmanteau smart artisan smartisan os unveiled march 27 2013 china national convention center compete miui xiaomi flyme os meizu chinese cellphone market first public beta available june 15 2013 initially compatible samsung galaxy iii plus devices followed smartisan hardware following year third-party devices supported may 2014 smartisan co. introduced first smartphone smartisan t1 year later august 26 2015 smartisan u1 announced smartisan os 2.0 taking likes oneplus 2 meizu m2 note may 2018 smartisan co. announced smartphone model r1 comes equipped smartisan os
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Operating systems
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vulnerability database vulnerability database platform aimed collecting maintaining disseminating information discovered computer security vulnerabilities database customarily describe identified vulnerability assess potential impact affected systems workarounds updates mitigate issue hacker surmount system information assurance three elements must apply susceptibility within system access susceptibility ability exploit susceptibility major vulnerability databases iss x-force database symantec securityfocus bid database open source vulnerability database osvdb osvdb shut april 2016 paid service vulndb took place aggregate broad range publicly disclosed vulnerabilities including common vulnerabilities exposures cve primary purpose cve run mitre attempt aggregate public vulnerabilities give standardized format unique identifier many vulnerability databases develop received intelligence cve investigate providing vulnerability risk scores impact ratings requisite workaround past cve paramount linking vulnerability databases critical patches debugs shared inhibit hackers accessing sensitive information private systems national vulnerability database nvd run national institute standards technology nist operated separately mitre-run cve database includes vulnerability information cve nvd serves enhancement data providing common vulnerability scoring system cvss risk scoring common platform enumeration cpe data open source vulnerability database provides accurate technical unbiased index vulnerability security comprehensive database cataloged 121,000 vulnerabilities spanning 113-year period osvdb founded august 2002 launched march 2004 primitive beginning newly identified vulnerabilities investigated site members explanations detailed website however necessity service thrived need dedicated staff resulted inception open security foundation osf founded non-profit organisation 2005 provide funding security projects primarily osvdb u.s. national vulnerability database comprehensive cyber security vulnerability database formed 2005 reports cve nvd primary cyber security referral tool individuals industries alike providing informative resources current vulnerabilities nvd holds excess 50,000 records publishes 13 new entries daily average similar osvdb nvd publishes impact ratings categorises material index provide users intelligible search system variety commercial companies also maintain vulnerability databases offering customers services deliver new updated vulnerability data machine-readable format well web portals examples include symantec deepsight portal vulnerability datafeed secunia purchased flexera vulnerability manager accenture vulnerability intelligence service formerly idefense vulnerability databases advise organisations develop prioritize execute patches mitigations endeavour rectify critical vulnerabilities however often lead creation additional susceptibilities patches created hastily thwart system exploitations violations depending upon level user organisation warrant appropriate access vulnerability database provides user disclosure known vulnerabilities may affect justification limiting access individuals impede hackers versed corporation system vulnerabilities could potentially exploited vulnerability databases contain vast array identified vulnerabilities however organisations possess expertise staff time revise remedy potential system susceptibilities hence vulnerability scoring method quantitatively determining severity system violation multitude scoring methods exist across vulnerability databases us-cert sans institute critical vulnerability analysis scale common vulnerability scoring system cvss prevailing technique vulnerability databases including osvdb vfeed nvd cvss based upon three primary metrics base temporal environmental provide vulnerability rating metric covers immutable properties vulnerability potential impact exposure confidential information accessibility information aftermath irretrievable deletion information temporal metrics denote mutable nature vulnerability example credibility exploitability current state system violation development workarounds could applied aspect cvss rates potential loss individuals organisations vulnerability furthermore details primary target vulnerability ranging personal systems large organisations number potentially affected individuals complication utilising different scoring systems consensus severity vulnerability thus different organisations may overlook critical system exploitations key benefit standardised scoring system like cvss published vulnerability scores assessed pursued remedied rapidly organisations individuals alike determine personal impact vulnerability system benefits derived vulnerability databases consumers organisations exponential information systems become increasingly embedded dependency reliance grows opportunity data exploitation although functionality database may appear unblemished without rigorous testing exiguous flaws allow hackers infiltrate system cyber security frequently databases published without stringent security controls hence sensitive material easily accessible database attacks recurrent form cyber security breaches recorded vulnerability databases sql nosql injections penetrate traditional information systems big data platforms respectively interpolate malicious statements allowing hackers unregulated system access established databases ordinarily fail implement crucial patches suggested vulnerability databases due excessive workload necessity exhaustive trialling ensure patches update defective system vulnerability database operators concentrate efforts major system deficiencies offers hackers unmitigated system access neglected patches databases require audit tracks record data amended accessed systems created without necessary auditing system exploitation system vulnerabilities challenging identify resolve vulnerability databases promulgate significance audit tracking deterrent cyber attacks data protection essential business personal financial information key asset purloining sensitive material discredit reputation firm implementation data protection strategies imperative guard confidential information hold view initial apathy software designers turn necessitates existence vulnerability databases systems devised greater diligence may impenetrable sql nosql injections making vulnerability databases redundant
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Computer security
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atatool atatool freeware software used display modify ata disk information microsoft windows environment software typically used manage host protected area hpa device configuration overlay dco features broadly similar hdparm linux recent versions include support dco restore freeze operations hpa security password operations simulated bad sectors atatool must run administrator privileges windows vista later requires elevated-privileges command prompt see user account control display detected hard disks display information hard disk 1 set hpa 10gb hard disk 1 volatile – lost next power cycle set hpa 10gb hard disk 1 non-volatile remove hpa 10gb hard disk 1 non-volatile set dco 5gb hard disk 1 remove dco hard disk 1 use atatool permanently change disk configuration may result permanent data loss making sectors disk inaccessible tool therefore used extreme care
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Computer security
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listaller listaller free computer software installation system similar package management system aimed making simple create package installed linux distributions well providing tools api make software management linux user-friendly listaller started december 2007 freedesktop.org developer matthias klumpp experimental project explore possibility writing universal user interface manage kinds linux software matter installed therefore listaller backends manage autopackage loki mojo native distribution packages original project provided one user interface manage kinds installed software interaction native distribution package management done via abstraction layer later replaced packagekit listaller also provided cross-distribution software installation format made easier create packages run multiple distributions installer part listaller also able assist installing autopackage packages first versions written object pascal although project started experiment soon evolved competitor autopackage mojo 2011 listaller never made stable release announcement appstream lot original listaller goals would achieved author decided change listaller away full software manager software installer joined forces appstream project pascal considered ideal language collaborate projects project already spent much time developing pascal bindings third-party libraries listaller rewritten vala subset original features main goal provide seamless integration appstream packagekit therefore universal software manager part removed project focuses creating cross-distro format distribution binary linux software nov 10 2014 matthias announced limba project limba supposed listaller next version listaller intended used installing binary pre-compiled versions non-core applications word processors web browsers personal computer games rather core libraries applications operating system shells listaller intended provide support installing system libraries security reasons listaller using package format so-called ipk packages short installation package lzma-compressed signed tarballs ipk packages contain small configuration files modify setup process provide logic scripts run install time parts setup process handled listaller built-in routines make possible distributors modify setup process 3rd-party applications comply policy necessary key value listaller integration desktop environments existing package management tools distributions therefore project provides several integration components default make possible manage listaller-installed 3rd-party applications software manager supports packagekit and/or appstream time discussed run installed 3rd-party tools sandbox default programs use listaller must also relocatable meaning must installable varying directories single binary makes possible listaller install software non-root users home directory although method enabled explicitly use encouraged listaller developer tools provide tools documentation application developers make software relocatable august 2010 projects announced merge consequence merge autopackage abandoned package binary package format user interfaces install autopackage packages autopackage tools like binreloc create relocatable applications apbuild developed part listaller project reason merging autopackage listaller mainly great lack developers projects decided join forces kde provides support listaller apper although distributors need explicitly enable using compile-time switch support gnome currently developed part gnome-packagekit suite theory distribution run packagekit 0.8.6 able provide listaller support ubuntu announced use listaller 3rd-party installer ubuntu phone develop ubuntu-specific solution instead
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Operating systems
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nokia e50 nokia e50 business device bar-style monoblock quad-band smartphone nokia announced 18 may 2006 part eseries intended primarily corporate business market includes sophisticated e-mail support nokia ’ intellisync wireless email blackberry connect visto mobile activesync mail exchange altexia well imap4 also ability view microsoft word powerpoint excel attachments pdf documents used editing without additional apps application manager downloads removes installs nokia third-party applications device device synchronization possible data transfer application features include edge bluetooth 2.0 1,280 × 960 pixels 1.3-megapixel camera microsd memory-card slot digital music video player functionality realplayer flash player unit support umts wi-fi fm radio uses third edition series 60 user-interface s60v3 symbian operating system version 9.1 binary compatible software compiled earlier versions symbian operating system check firmware v 07.36.0.0
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Operating systems
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sciengines gmbh sciengines gmbh privately owned company founded 2007 spin-off copacobana project universities bochum kiel germany project intended create platform affordable custom hardware attack copacobana massively-parallel reconfigurable computer utilized perform so-called brute force attack recover des encrypted data consists 120 commercially available reconfigurable integrated circuits fpgas xilinx spartan3-1000 run parallel create massively parallel system since 2007 sciengines gmbh enhanced developed successors copacobana furthermore copacobana become well known reference platform cryptanalysis custom hardware based attacks symmetric asymmetric cyphers stream ciphers 2008 attacks a5/1 stream cipher encryption system used encrypt voice streams gsm published first known real world attack utilizing off-the-shelf custom hardware introduced 2008 rivyera s3-5000 enhancing performance computer dramatically via using 128 spartan-3 5000 currently sciengines rivyera holds record brute-force breaking des utilizing 128 spartan-3 5000 fpgas current systems provide unique density 256 spartan-6 fpgas per single system enabling scientific utilization beyond field cryptanalysis like bioinformatics providing standard off-the-shelf intel cpu mainboard integrated fpga computer rivyera systems allow execute standard code without modifications sciengines aims programmers focus porting time consuming 5 code fpga therefore bundle eclipse like development environment allows code implementation hardware based implementation languages e.g vhdl verilog well c based languages application programming interface c c++ java fortran allow scientists programmers adopt code benefit application-specific hardware architecture
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Computer security
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nuix nuix pty ltd australian technology company produces software platform indexing searching analyzing extracting knowledge unstructured data applications include digital investigation cybersecurity e-discovery information governance email migration privacy january 2017 software platform reportedly used least 1800 customers 65 countries company headquarters sydney australia offices conshohocken herndon san francisco new york united states cork ireland london united kingdom nuix founded 2000 goal make vast quantities unstructured data easily searchable 2006 company grew two developers 400 employees 2010 nuix awarded five-year contract securities exchange commission 2014 company appointed industry partner international multilateral partnership cyber threats 2017 nuix board directors appointed rod vawdrey position chief executive officer nuix markets ediscovery digital investigation security intelligence information governance solutions based nuix engine nuix engine combines load balancing fault tolerance processing technologies provide insights large volumes unstructured semi-structured structured data several features nuix engine granted patent 2011 november 2016 nuix announced new analysis platform called nuix insight analytics intelligence endpoint security product nuix insight adaptive security integrates cybersecurity threat prevention detection response remediation deception nuix donated software licences training international consortium investigative journalists icij used nuix investigate offshore leaks data süddeutsche zeitung icij also used analyze panama papers using nuix software panama papers investigation team made 2.6 terabytes scanned documents text-searchable extracted metadata helped journalists cross-reference people places business entities across documents october 2015 nuix reported raised 250,000 room read philanthropic product proof finder nuix largest shareholder macquarie group shareholding approximately 70
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Computer security
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advanced computing environment advanced computing environment ace defined industry consortium early 1990s next generation commodity computing platform successor personal computers based intel 32-bit instruction set architecture effort found little support market dissolved due lack sales infighting within group consortium announced 9th april 1991 compaq microsoft mips computer systems digital equipment corporation santa cruz operation time widely believed risc-based systems would maintain price/performance advantage ad hoc wintel systems however also widely believed windows nt would quickly displace many operating systems combined effects wide selection software ease building wintel machines supported ace formed provide alternative platform wintel providing viable alternative advantages terms software support greater advantages terms performance environment standardized mips architecture two operating systems sco unix open desktop would become windows nt originally named os/2 3.0 advanced risc computing arc document produced give hardware firmware specifications platform members consortium included acer control data corporation kubota nec corporation nkk olivetti prime computer pyramid technology siemens silicon graphics sony sumitomo tandem computers wang laboratories zenith data systems besides large companies several start-up companies built ace-compliant systems well companies involved reasons joining ace effort initiative used microprocessor companies attempt take market share away intel system companies used initiative attempt take market share away workstation leader sun microsystems soon initiative announced dissenting faction seven ace members declared decision support little-endian architectures short-sighted subgroup known apache group promoted big-endian alternative group whose name conceived pun big indian unrelated later apache software foundation later adopted name mips/open rift within ace consortium averted decided add support big-endian svr4 even ace initiative consortium began fall apart little year started became apparent mass market alternative wintel computing platform upstart platforms offer enough performance improvement incumbent pc major cost disadvantages systems due low volume production initiative started risc based systems running 100-200 mhz time substantial performance advantage intel 80486 original pentium chips running approximately 60 mhz time intel quickly migrated pentium design newer semiconductor process generations performance operating frequency advantage slipped away compaq first company leave consortium stating departure ceo rod canion one primary backers behind formation ace shifting priorities away higher-end systems followed short order sco announcing suspending work moving version unix mips platform potential conflicts earlier year mips purchased sgi may also contributed concerns neutrality target platform dec released alpha processor less interested promoting competing architecture finally significant improvements intel x86 performance made abandoning less attractive although ace supported x86 time intel never member main product ace group advanced risc computing specification arc initially based mips-based computer hardware firmware environment although ace went defunct computer ever manufactured fully complied arc standard arc system still exerts widespread legacy microsoft windows nt-based operating systems windows xp used arc conventions naming boot devices windows vista sgi used modified version arc firmware calls arcs systems sgi computers run irix 6.1 later indy octane etc boot arcs console uses drive naming conventions windows accordingly addition various risc-based computers designed run windows nt used versions arc boot console boot nt among computers also predicted intel ia-32-based computers would adopt arc console although sgi ever marketed ia-32-based machines arc firmware namely sgi visual workstation series went sale 1999 products complying degree arc standard include
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Computer architecture
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