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Cryptography	since development rotor cipher machines world war advent computers world war ii cryptography methods become increasingly complex applications varied.modern cryptography heavily based mathematical theory computer science practice cryptographic algorithms designed around computational hardness assumptions making algorithms hard break actual practice adversary.theoretically possible break welldesigned system infeasible actual practice so.schemes well designed therefore termed computationally secure theoretical advances e.g.improvements integer factorization algorithms faster computing technology require designs continually reevaluated necessary adapted.informationtheoretically secure schemes provably cannot broken even unlimited computing power onetime pad much difficult use practice best theoretically breakable computationally secure schemes.the growth cryptographic technology raised number legal issues information age.
Cryptography	cryptographys potential use tool espionage sedition led many governments classify weapon limit even prohibit use export.jurisdictions use cryptography legal laws permit investigators compel disclosure encryption keys documents relevant investigation.cryptography also plays major role digital rights management copyright infringement disputes regard digital media.terminology first use term cryptograph opposed cryptogram dates back th century—originating goldbug story edgar allan poe.until modern times cryptography referred almost exclusively encryption process converting ordinary information called plaintext unintelligible form called ciphertext.decryption reverse words moving unintelligible ciphertext back plaintext.
Cryptography	cipher cypher pair algorithms carry encryption reversing decryption.detailed operation cipher controlled algorithm instance key.key secret ideally known communicants usually string characters ideally short remembered user needed decrypt ciphertext.formal mathematical terms cryptosystem ordered list elements finite possible plaintexts finite possible cyphertexts finite possible keys encryption decryption algorithms correspond key.keys important formally actual practice ciphers without variable keys trivially broken knowledge cipher used therefore useless even counterproductive purposes.
Cryptography	historically ciphers often used directly encryption decryption without additional procedures authentication integrity checks.two main types cryptosystems symmetric asymmetric.symmetric systems ones known secret key encrypts decrypts message.data manipulation symmetric systems significantly faster asymetric systems.asymmetric systems use public key encrypt message related private key decrypt it.
Cryptography	advantage asymmetric systems public key freely published allowing parties establish secure communication without shared secret key.practice asymmetric systems used first exchange secret key secure communication proceeds via efficient symmetric system using key.examples asymmetric systems include diffie–hellman key exchange rsa rivest–shamir–adleman ecc elliptic curve cryptography postquantum cryptography.secure symmetric algorithms include commonly used aes advanced encryption standard replaced older des data encryption standard.insecure symmetric algorithms include childrens language tangling schemes pig latin cant historical cryptographic schemes however seriously intended prior invention onetime pad early th century.in colloquial use term code often used mean method encryption concealment meaning.
Cryptography	however cryptography code specific meaning replacement unit plaintext i.e.meaningful word phrase code word example wallaby replaces attack dawn.cypher contrast scheme changing substituting element level letter syllable pair letters etc.order produce cyphertext.cryptanalysis term used study methods obtaining meaning encrypted information without access key normally required i.e.study crack encryption algorithms implementations.some use terms cryptography cryptology interchangeably english others including us military practice generally use cryptography refer specifically use practice cryptographic techniques cryptology refer combined study cryptography cryptanalysis.
Cryptography	english flexible several languages cryptology done cryptologists always used second sense above.rfc advises steganography sometimes included cryptology.the study characteristics languages application cryptography cryptology e.g.frequency data letter combinations universal patterns etc.called cryptolinguistics.history cryptography cryptanalysis modern era cryptography focused message confidentiality i.e.
Cryptography	encryption—conversion messages comprehensible form incomprehensible one back end rendering unreadable interceptors eavesdroppers without secret knowledge namely key needed decryption message.encryption attempted ensure secrecy communications spies military leaders diplomats.recent decades field expanded beyond confidentiality concerns include techniques message integrity checking senderreceiver identity authentication digital signatures interactive proofs secure computation among others.classic cryptography main classical cipher types transposition ciphers rearrange order letters message e.g.hello world becomes ehlol owrdl trivially simple rearrangement scheme substitution ciphers systematically replace letters groups letters letters groups letters e.g.
Cryptography	fly becomes gmz bu podf replacing letter one following latin alphabet.simple versions either never offered much confidentiality enterprising opponents.early substitution cipher caesar cipher letter plaintext replaced letter fixed number positions alphabet.suetonius reports julius caesar used shift three communicate generals.atbash example early hebrew cipher.
Cryptography	earliest known use cryptography carved ciphertext stone egypt ca bce may done amusement literate observers rather way concealing information.the greeks classical times said known ciphers e.g.scytale transposition cipher claimed used spartan military.steganography i.e.hiding even existence message keep confidential also first developed ancient times.early example herodotus message tattooed slaves shaved head concealed regrown hair.
Cryptography	modern examples steganography include use invisible ink microdots digital watermarks conceal information.in india yearold kamasutra vātsyāyana speaks two different kinds ciphers called kautiliyam mulavediya.kautiliyam cipher letter substitutions based phonetic relations vowels becoming consonants.mulavediya cipher alphabet consists pairing letters using reciprocal ones.in sassanid persia two secret scripts according muslim author ibn alnadim šāhdabīrīya literally kings script used official correspondence rāzsaharīya used communicate secret messages countries.david kahn notes codebreakers modern cryptology originated among arabs first people systematically document cryptanalytic methods.alkhalil – wrote book cryptographic messages contains first use permutations combinations list possible arabic words without vowels.ciphertexts produced classical cipher modern ciphers reveal statistical information plaintext information often used break cipher.discovery frequency analysis perhaps arab mathematician polymath alkindi also known alkindus th century nearly ciphers could broken informed attacker.
Cryptography	classical ciphers still enjoy popularity today though mostly puzzles see cryptogram.alkindi wrote book cryptography entitled risalah fi istikhraj almuamma manuscript deciphering cryptographic messages described first known use frequency analysis cryptanalysis techniques.language letter frequencies may offer little help extended historical encryption techniques homophonic cipher tend flatten frequency distribution.ciphers language letter group ngram frequencies may provide attack.essentially ciphers remained vulnerable cryptanalysis using frequency analysis technique development polyalphabetic cipher clearly leon battista alberti around year though indication already known alkindi.albertis innovation use different ciphers i.e.substitution alphabets various parts message perhaps successive plaintext letter limit.
Cryptography	also invented probably first automatic cipher device wheel implemented partial realization invention.vigenère cipher polyalphabetic cipher encryption uses key word controls letter substitution depending letter key word used.midth century charles babbage showed vigenère cipher vulnerable kasiski examination first published ten years later friedrich kasiski.although frequency analysis powerful general technique many ciphers encryption still often effective practice many wouldbe cryptanalyst unaware technique.breaking message without using frequency analysis essentially required knowledge cipher used perhaps key involved thus making espionage bribery burglary defection etc.attractive approaches cryptanalytically uninformed.
Cryptography	finally explicitly recognized th century secrecy ciphers algorithm sensible practical safeguard message security fact realized adequate cryptographic scheme including ciphers remain secure even adversary fully understands cipher algorithm itself.security key used alone sufficient good cipher maintain confidentiality attack.fundamental principle first explicitly stated auguste kerckhoffs generally called kerckhoffss principle alternatively bluntly restated claude shannon inventor information theory fundamentals theoretical cryptography shannons maxim—the enemy knows system.different physical devices aids used assist ciphers.one earliest may scytale ancient greece rod supposedly used spartans aid transposition cipher.medieval times aids invented cipher grille also used kind steganography.
Cryptography	invention polyalphabetic ciphers came sophisticated aids albertis cipher disk johannes trithemius tabula recta scheme thomas jeffersons wheel cypher publicly known reinvented independently bazeries around .many mechanical encryptiondecryption devices invented early th century several patented among rotor machines—famously including enigma machine used german government military late world war ii.ciphers implemented better quality examples machine designs brought substantial increase cryptanalytic difficulty wwi.computer era prior early th century cryptography mainly concerned linguistic lexicographic patterns.since emphasis shifted cryptography makes extensive use mathematics including aspects information theory computational complexity statistics combinatorics abstract algebra number theory finite mathematics generally.
Cryptography	cryptography also branch engineering unusual one since deals active intelligent malevolent opposition kinds engineering e.g.civil chemical engineering need deal neutral natural forces.also active research examining relationship cryptographic problems quantum physics.just development digital computers electronics helped cryptanalysis made possible much complex ciphers.furthermore computers allowed encryption kind data representable binary format unlike classical ciphers encrypted written language texts new significant.computer use thus supplanted linguistic cryptography cipher design cryptanalysis.
Cryptography	many computer ciphers characterized operation binary bit sequences sometimes groups blocks unlike classical mechanical schemes generally manipulate traditional characters i.e.letters digits directly.however computers also assisted cryptanalysis compensated extent increased cipher complexity.nonetheless good modern ciphers stayed ahead cryptanalysis typically case use quality cipher efficient i.e.fast requiring resources memory cpu capability breaking requires effort many orders magnitude larger vastly larger required classical cipher making cryptanalysis inefficient impractical effectively impossible.
Cryptography	advent modern cryptography cryptanalysis new mechanical devices proved difficult laborious.united kingdom cryptanalytic efforts bletchley park wwii spurred development efficient means carrying repetitious tasks.culminated development colossus worlds first fully electronic digital programmable computer assisted decryption ciphers generated german armys lorenz sz machine.extensive open academic research cryptography relatively recent beginning mids.early ibm personnel designed data encryption standard des algorithm became first federal government cryptography standard united states.whitfield diffie martin hellman published diffie–hellman key exchange algorithm.
Cryptography	rsa algorithm published martin gardners scientific american column.since cryptography become widely used tool communications computer networks computer security generally.some modern cryptographic techniques keep keys secret certain mathematical problems intractable integer factorization discrete logarithm problems deep connections abstract mathematics.cryptosystems proven unconditionally secure.onetime pad one proven claude shannon.important algorithms proven secure certain assumptions.
Cryptography	example infeasibility factoring extremely large integers basis believing rsa secure systems even proof unbreakability unavailable since underlying mathematical problem remains open.practice widely used believed unbreakable practice competent observers.systems similar rsa one michael o. rabin provably secure provided factoring n pq impossible quite unusable practice.discrete logarithm problem basis believing cryptosystems secure related less practical systems provably secure relative solvability insolvability discrete log problem.as well aware cryptographic history cryptographic algorithm system designers must also sensibly consider probable future developments working designs.instance continuous improvements computer processing power increased scope bruteforce attacks specifying key lengths required key lengths similarly advancing.
Cryptography	potential impact quantum computing already considered cryptographic system designers developing postquantum cryptography.announced imminence small implementations machines may making need preemptive caution rather merely speculative.modern cryptography symmetrickey cryptography symmetrickey cryptography refers encryption methods sender receiver share key less commonly keys different related easily computable way.kind encryption publicly known june .symmetric key ciphers implemented either block ciphers stream ciphers.block cipher enciphers input blocks plaintext opposed individual characters input form used stream cipher.the data encryption standard des advanced encryption standard aes block cipher designs designated cryptography standards us government though dess designation finally withdrawn aes adopted.
Cryptography	despite deprecation official standard des especially stillapproved much secure tripledes variant remains quite popular used across wide range applications atm encryption email privacy secure remote access.many block ciphers designed released considerable variation quality.many even designed capable practitioners thoroughly broken feal.stream ciphers contrast block type create arbitrarily long stream key material combined plaintext bitbybit characterbycharacter somewhat like onetime pad.stream cipher output stream created based hidden internal state changes cipher operates.internal state initially set using secret key material.
Cryptography	rc widely used stream cipher.block ciphers used stream ciphers generating blocks keystream place pseudorandom number generator applying xor operation bit plaintext bit keystream.message authentication codes macs much like cryptographic hash functions except secret key used authenticate hash value upon receipt additional complication blocks attack scheme bare digest algorithms thought worth effort.cryptographic hash functions third type cryptographic algorithm.take message length input output short fixedlength hash used example digital signature.good hash functions attacker cannot find two messages produce hash.
Cryptography	md longused hash function broken md strengthened variant md also widely used broken practice.us national security agency developed secure hash algorithm series mdlike hash functions sha flawed algorithm agency withdrew sha widely deployed secure md cryptanalysts identified attacks sha family improves sha vulnerable clashes us standards authority thought prudent security perspective develop new standard significantly improve robustness nists overall hash algorithm toolkit.thus hash function design competition meant select new u.s. national standard called sha .competition ended october nist announced keccak would new sha hash algorithm.unlike block stream ciphers invertible cryptographic hash functions produce hashed output cannot used retrieve original input data.
Cryptography	cryptographic hash functions used verify authenticity data retrieved untrusted source add layer security.publickey cryptography symmetrickey cryptosystems use key encryption decryption message although message group messages different key others.significant disadvantage symmetric ciphers key management necessary use securely.distinct pair communicating parties must ideally share different key perhaps ciphertext exchanged well.number keys required increases square number network members quickly requires complex key management schemes keep consistent secret.
Cryptography	groundbreaking paper whitfield diffie martin hellman proposed notion publickey also generally called asymmetric key cryptography two different mathematically related keys used—a public key private key.public key system constructed calculation one key private key computationally infeasible public key even though necessarily related.instead keys generated secretly interrelated pair.historian david kahn described publickey cryptography revolutionary new concept field since polyalphabetic substitution emerged renaissance.in publickey cryptosystems public key may freely distributed paired private key must remain secret.publickey encryption system public key used encryption private secret key used decryption.
Cryptography	diffie hellman could find system showed publickey cryptography indeed possible presenting diffie–hellman key exchange protocol solution widely used secure communications allow two parties secretly agree shared encryption key.the x. standard defines commonly used format public key certificates.diffie hellmans publication sparked widespread academic efforts finding practical publickey encryption system.race finally ronald rivest adi shamir len adleman whose solution since become known rsa algorithm.the diffie–hellman rsa algorithms addition first publicly known examples highquality publickey algorithms among widely used.asymmetrickey algorithms include cramer–shoup cryptosystem elgamal encryption various elliptic curve techniques.a document published government communications headquarters gchq british intelligence organization revealed cryptographers gchq anticipated several academic developments.reportedly around james h. ellis conceived principles asymmetric key cryptography.clifford cocks invented solution similar design rationale rsa.
Cryptography	malcolm j. williamson claimed developed diffie–hellman key exchange.publickey cryptography also used implementing digital signature schemes.digital signature reminiscent ordinary signature characteristic easy user produce difficult anyone else forge.digital signatures also permanently tied content message signed cannot moved one document another attempt detectable.digital signature schemes two algorithms one signing secret key used process message hash message one verification matching public key used message check validity signature.rsa dsa two popular digital signature schemes.
Cryptography	digital signatures central operation public key infrastructures many network security schemes e.g.ssltls many vpns etc..publickey algorithms often based computational complexity hard problems often number theory.example hardness rsa related integer factorization problem diffie–hellman dsa related discrete logarithm problem.security elliptic curve cryptography based number theoretic problems involving elliptic curves.difficulty underlying problems publickey algorithms involve operations modular multiplication exponentiation much computationally expensive techniques used block ciphers especially typical key sizes.
Cryptography	result publickey cryptosystems commonly hybrid cryptosystems fast highquality symmetrickey encryption algorithm used message relevant symmetric key sent message encrypted using publickey algorithm.similarly hybrid signature schemes often used cryptographic hash function computed resulting hash digitally signed.cryptographic hash functions cryptographic hash functions cryptographic algorithms ways generate utilize specific keys encrypt data either symmetric asymmetric encryption functions may viewed keys themselves.take message length input output short fixedlength hash used example digital signature.good hash functions attacker cannot find two messages produce hash.
Cryptography	md longused hash function broken md strengthened variant md also widely used broken practice.us national security agency developed secure hash algorithm series mdlike hash functions sha flawed algorithm agency withdrew sha widely deployed secure md cryptanalysts identified attacks sha family improves sha vulnerable clashes us standards authority thought prudent security perspective develop new standard significantly improve robustness nists overall hash algorithm toolkit.thus hash function design competition meant select new u.s. national standard called sha .competition ended october nist announced keccak would new sha hash algorithm.unlike block stream ciphers invertible cryptographic hash functions produce hashed output cannot used retrieve original input data.
Cryptography	cryptographic hash functions used verify authenticity data retrieved untrusted source add layer security.cryptanalysis goal cryptanalysis find weakness insecurity cryptographic scheme thus permitting subversion evasion.it common misconception every encryption method broken.connection wwii work bell labs claude shannon proved onetime pad cipher unbreakable provided key material truly random never reused kept secret possible attackers equal greater length message.ciphers apart onetime pad broken enough computational effort brute force attack amount effort needed may exponentially dependent key size compared effort needed make use cipher.cases effective security could achieved proven effort required i.e.
Cryptography	work factor shannons terms beyond ability adversary.means must shown efficient method opposed timeconsuming brute force method found break cipher.since proof found date onetimepad remains theoretically unbreakable cipher.although wellimplemented onetimepad encryption cannot broken traffic analysis still possible.there wide variety cryptanalytic attacks classified several ways.common distinction turns eve attacker knows capabilities available.
Cryptography	ciphertextonly attack eve access ciphertext good modern cryptosystems usually effectively immune ciphertextonly attacks.knownplaintext attack eve access ciphertext corresponding plaintext many pairs.chosenplaintext attack eve may choose plaintext learn corresponding ciphertext perhaps many times example gardening used british wwii.chosenciphertext attack eve may able choose ciphertexts learn corresponding plaintexts.finally maninthemiddle attack eve gets alice sender bob recipient accesses modifies traffic forwards recipient.
Cryptography	also important often overwhelmingly mistakes generally design use one protocols involved.cryptanalysis symmetrickey ciphers typically involves looking attacks block ciphers stream ciphers efficient attack could perfect cipher.example simple brute force attack des requires one known plaintext decryptions trying approximately half possible keys reach point chances better even key sought found.may enough assurance linear cryptanalysis attack des requires known plaintexts corresponding ciphertexts approximately des operations.considerable improvement brute force attacks.publickey algorithms based computational difficulty various problems.famous difficulty integer factorization semiprimes difficulty calculating discrete logarithms yet proven solvable polynomial time p using classical turingcomplete computer.
Cryptography	much publickey cryptanalysis concerns designing algorithms p solve problems using technologies quantum computers.instance bestknown algorithms solving elliptic curvebased version discrete logarithm much timeconsuming bestknown algorithms factoring least problems less equivalent size.thus achieve equivalent strength encryption techniques depend upon difficulty factoring large composite numbers rsa cryptosystem require larger keys elliptic curve techniques.reason publickey cryptosystems based elliptic curves become popular since invention mids.while pure cryptanalysis uses weaknesses algorithms attacks cryptosystems based actual use algorithms real devices called sidechannel attacks.cryptanalyst access example amount time device took encrypt number plaintexts report error password pin character may able use timing attack break cipher otherwise resistant analysis.
Cryptography	attacker might also study pattern length messages derive valuable information known traffic analysis quite useful alert adversary.poor administration cryptosystem permitting short keys make system vulnerable regardless virtues.social engineering attacks humans e.g.bribery extortion blackmail espionage torture ... usually employed due costeffective feasible perform reasonable amount time compared pure cryptanalysis high margin.cryptographic primitives much theoretical work cryptography concerns cryptographic primitives—algorithms basic cryptographic properties—and relationship cryptographic problems.
Cryptography	complicated cryptographic tools built basic primitives.primitives provide fundamental properties used develop complex tools called cryptosystems cryptographic protocols guarantee one highlevel security properties.note however distinction cryptographic primitives cryptosystems quite arbitrary example rsa algorithm sometimes considered cryptosystem sometimes primitive.typical examples cryptographic primitives include pseudorandom functions oneway functions etc.cryptosystems one cryptographic primitives often used develop complex algorithm called cryptographic system cryptosystem.
Cryptography	cryptosystems e.g.elgamal encryption designed provide particular functionality e.g.public key encryption guaranteeing certain security properties e.g.chosenplaintext attack cpa security random oracle model.cryptosystems use properties underlying cryptographic primitives support systems security properties.
Cryptography	distinction primitives cryptosystems somewhat arbitrary sophisticated cryptosystem derived combination several primitive cryptosystems.many cases cryptosystems structure involves back forth communication among two parties space e.g.sender secure message receiver across time e.g.cryptographically protected backup data.cryptosystems sometimes called cryptographic protocols.some widely known cryptosystems include rsa schnorr signature elgamal encryption pretty good privacy pgp.
Cryptography	complex cryptosystems include electronic cash systems signcryption systems etc.theoretical cryptosystems include interactive proof systems like zeroknowledge proofs systems secret sharing etc.lightweight cryptography lightweight cryptography lwc concerns cryptographic algorithms developed strictly constrained environment.growth internet things iot spiked research development lightweight algorithms better suited environment.iot environment requires strict constraints power consumption processing power security.
Cryptography	algorithms present aes speck examples many lwc algorithms developed achieve standard set national institute standards technology.applications general ensure secrecy transmission many systems use private key cryptography protect transmitted information.publickey systems one maintain secrecy without master key large number keys.cybersecurity cryptography used secure communications encrypting them.websites use encryption via https.
Cryptography	endtoend encryption sender receiver read messages implemented email pretty good privacy secure messaging general signal whatsapp.operating systems use encryption keep passwords secret conceal parts system ensure software updates truly system maker.instead storing plaintext passwords computer systems store hashes thereof user logs system passes given password cryptographic hash function compares hashed value file.manner neither system attacker point access password plaintext.encryption sometimes used encrypt ones entire drive.example university college london implemented bitlocker program microsoft render drive data opaque without users logging in.electronic money blockchain cryptocurrency social issues legal issues prohibitions cryptography long interest intelligence gathering law enforcement agencies.
Cryptography	secret communications may criminal even treasonous.facilitation privacy diminution privacy attendant prohibition cryptography also considerable interest civil rights supporters.accordingly history controversial legal issues surrounding cryptography especially since advent inexpensive computers made widespread access highquality cryptography possible.in countries even domestic use cryptography restricted.france significantly restricted use cryptography domestically though since relaxed many rules.china iran license still required use cryptography.
Cryptography	many countries tight restrictions use cryptography.among restrictive laws belarus kazakhstan mongolia pakistan singapore tunisia vietnam.in united states cryptography legal domestic use much conflict legal issues related cryptography.one particularly important issue export cryptography cryptographic software hardware.probably importance cryptanalysis world war ii expectation cryptography would continue important national security many western governments point strictly regulated export cryptography.world war ii illegal us sell distribute encryption technology overseas fact encryption designated auxiliary military equipment put united states munitions list.
Cryptography	development personal computer asymmetric key algorithms i.e.public key techniques internet especially problematic.however internet grew computers became widely available highquality encryption techniques became well known around globe.export controls several challenges us export regulation cryptography.source code philip zimmermanns pretty good privacy pgp encryption program found way onto internet june complaint rsa security called rsa data security inc. resulted lengthy criminal investigation zimmermann us customs service fbi though charges ever filed.
Cryptography	daniel j. bernstein graduate student uc berkeley brought lawsuit us government challenging aspects restrictions based free speech grounds.case bernstein v. united states ultimately resulted decision printed source code cryptographic algorithms systems protected free speech united states constitution.in thirtynine countries signed wassenaar arrangement arms control treaty deals export arms dualuse technologies cryptography.treaty stipulated use cryptography short keylengths bit symmetric encryption bit rsa would longer exportcontrolled.cryptography exports us became less strictly regulated consequence major relaxation longer many restrictions key sizes usexported massmarket software.since relaxation us export restrictions personal computers connected internet include ussourced web browsers firefox internet explorer almost every internet user worldwide potential access quality cryptography via browsers e.g.
Cryptography	via transport layer security.mozilla thunderbird microsoft outlook email client programs similarly transmit receive emails via tls send receive email encrypted smime.many internet users dont realize basic application software contains extensive cryptosystems.browsers email programs ubiquitous even governments whose intent regulate civilian use cryptography generally dont find practical much control distribution use cryptography quality even laws force actual enforcement often effectively impossible.nsa involvement another contentious issue connected cryptography united states influence national security agency cipher development policy.
Cryptography	nsa involved design des development ibm consideration national bureau standards possible federal standard cryptography.des designed resistant differential cryptanalysis powerful general cryptanalytic technique known nsa ibm became publicly known rediscovered late s. according steven levy ibm discovered differential cryptanalysis kept technique secret nsas request.technique became publicly known biham shamir rediscovered announced years later.entire affair illustrates difficulty determining resources knowledge attacker might actually have.another instance nsas involvement clipper chip affair encryption microchip intended part capstone cryptographycontrol initiative.clipper widely criticized cryptographers two reasons.
Cryptography	cipher algorithm called skipjack classified declassified long clipper initiative lapsed.classified cipher caused concerns nsa deliberately made cipher weak order assist intelligence efforts.whole initiative also criticized based violation kerckhoffss principle scheme included special escrow key held government use law enforcement i.e.wiretapping.digital rights management cryptography central digital rights management drm group techniques technologically controlling use copyrighted material widely implemented deployed behest copyright holders.
Cryptography	u.s. president bill clinton signed digital millennium copyright act dmca criminalized production dissemination use certain cryptanalytic techniques technology known later discovered specifically could used circumvent drm technological schemes.noticeable impact cryptography research community since argument made cryptanalytic research violated dmca.similar statutes since enacted several countries regions including implementation eu copyright directive.similar restrictions called treaties signed world intellectual property organization memberstates.the united states department justice fbi enforced dmca rigorously feared law nonetheless remains controversial one.niels ferguson wellrespected cryptography researcher publicly stated release research intel security design fear prosecution dmca.
Cryptography	cryptologist bruce schneier argued dmca encourages vendor lockin inhibiting actual measures toward cybersecurity.alan cox longtime linux kernel developer edward felten students princeton encountered problems related act.dmitry sklyarov arrested visit us russia jailed five months pending trial alleged violations dmca arising work done russia work legal.cryptographic keys responsible bluray hd dvd content scrambling discovered released onto internet.cases motion picture association america sent numerous dmca takedown notices massive internet backlash triggered perceived impact notices fair use free speech.
Cryptography	forced disclosure encryption keys united kingdom regulation investigatory powers act gives uk police powers force suspects decrypt files hand passwords protect encryption keys.failure comply offense right punishable conviction twoyear jail sentence five years cases involving national security.successful prosecutions occurred act first resulted term months imprisonment.similar forced disclosure laws australia finland france india compel individual suspects investigation hand encryption keys passwords criminal investigation.in united states federal criminal case united states v. fricosu addressed whether search warrant compel person reveal encryption passphrase password.electronic frontier foundation eff argued violation protection selfincrimination given fifth amendment.
Cryptography	court ruled writs act defendant required produce unencrypted hard drive court.in many jurisdictions legal status forced disclosure remains unclear.the fbi–apple encryption dispute concerns ability courts united states compel manufacturers assistance unlocking cell phones whose contents cryptographically protected.as potential countermeasure forced disclosure cryptographic software supports plausible deniability encrypted data indistinguishable unused random data example drive securely wiped.see also outline cryptography – overview topical guide cryptographylist cryptographers – wikipedia list articlelist important publications cryptography – wikipedia list articlelist multiple discoveries – wikipedia list articlelist unsolved problems computer science – wikipedia list articlesyllabical steganographical table – eighteenthcentury work believed first cryptography chart – first cryptography chartcomparison cryptography librariescrypto warsencyclopedia cryptography security – book technische universiteit eindhovenglobal surveillance – mass surveillance across national bordersindistinguishability obfuscation – type cryptographic software obfuscationinformation theory – scientific study digital informationstrong cryptography – term applied cryptographic systems highly resistant cryptanalysisworld wide web consortiums web cryptography api – world wide web consortium cryptography standardcollision attack references reading external links dictionary definition cryptography wiktionary media related cryptography wikimedia commonscryptography time bbccrypto glossary dictionary technical cryptographynsas cryptokids.overview applications cryptology cryptool team pdf .mb.july course cryptography raphael pass abhi shelat – offered cornell form lecture notes.for use cryptographic elements fiction see dooley john f. william marilyn ingersoll professor computer science knox college august .cryptology fiction.
Wuala	archived original july .retrieved february .the george fabyan collection library congress early editions works seventeenthcentury english literature publications relating cryptography.service stores files data centres provided wuala multiple european countries france germany switzerland.earlier version also supported distributed storage users machines however feature dropped.august wuala announced discontinuing service stored data would deleted november .wuala recommended rival cloud storage startup tresorit alternative remaining customers.history research development occurred swiss federal institute technology eth zürich.
Wuala	august open betajavaapplet available website could run web browser.september wuala webstart project registered sourceforge.net.october alpha release rest api early stage development supported http get requests content either public shared keyed hyperlink.december uniform resource locator changed httpwua.la archived wayback machine http files public shared keyed hyperlink made accessible web browsers.march lacie announced merger caleido ag.
Wuala	wuala described merger wuala lacie caleido ag lacie.january postmerger announcement first joint products.may pro features backup sync file versioning time travel available everyone cost september trade storage feature discontinued.june storage plan shifted paidonly service october wuala announced existing freeonly storage would terminated end customers wishing save data migrate away purchase paid plan august wuala announced would allow renewals purchase storage.service transition readonly september stored data deleted november features registered user cankeep files privateshare files registered usersshare files unregistered users keyed hyperlinkpublish filesbackupfile synchronizationfile versioning.registered unregistered users receive streaming media.when user adds file wuala saves changes file served wuala users local copy file first encrypted chunked redundant fragments using reedsolomon error correction codes.
Wuala	fragments uploaded data centers.storage wuala offered free accounts gb storage charge.june shifted paidonly service.end longer support form freeonly storage shifting entirely payment based usage model.users joint products may start greater amounts storage limited periodwith lacie external hard disk drive gb one yearor lacie usb flash drive gb two years.additional storage may bought.june referral system shut due new paidonly policy.for bought storage prices range euryear gb euryear tb.pricing changed june storage plan starts .
Wuala	€ per month € per year gb ends .€ per month € per year tb storage.trading one distinguishing features wuala ability trade local disk storage space cloud storage longer available.user interfaces desktop application user interface offers features normally associated file manager.additional features come integration.a registered user install javabased client application swtguion number linux mac os x microsoft windows computerswith fuse macfuse dokan respectively file system integration.
Wuala	wuala webstart web browsers web browser computer java installedthe user starttrust java applet downloads runs class loader allowing fast start latest version wuala application.if computer without java running class loader preventedany folder public shared weblink browsed.nongraphical interfaces support following may limitedcommandline interfacedaemonheadless system security according wualas faq software uses aes encryption rsa key exchange signatures.keys organized key management scheme called cryptree.according faq wuala employs full clientside encryption.files metadata – os x metadata supported – get encrypted uploaded.encryption key stored one even lacie operates service decrypt stored files.
Wuala	disadvantage wuala password recovery data processing needs done client example creating search index.advantage significantly improved privacy.since source code wuala released difficult ensure software states including proper clientside encryption.also updates pushed automatically client machine.facts mean users wuala safe possible backdoors code.reviews unlimited online storage free almost wuala webware cnet online storage wuala linux journal wuala makes online storage social news opinion pcmag.com wuala pp online storage service goes live download squad three days check wualas social grid storage techcrunch see also comparison file synchronization softwarelist online backup servicescomparison online backup services notes references external links official website
Picture archiving and communication system	electronic images reports transmitted digitally via pacs eliminates need manually file retrieve transport film jackets folders used store protect xray film.universal format pacs image storage transfer dicom digital imaging communications medicine.nonimage data scanned documents may incorporated using consumer industry standard formats like pdf portable document format encapsulated dicom.pacs consists four major components imaging modalities xray plain film pf computed tomography ct magnetic resonance imaging mri secured network transmission patient information workstations interpreting reviewing images archives storage retrieval images reports.combined available emerging web technology pacs ability deliver timely efficient access images interpretations related data.
Picture archiving and communication system	pacs reduces physical time barriers associated traditional filmbased image retrieval distribution display.types images pacs handle images various medical imaging instruments including ultrasound us magnetic resonance mr nuclear medicine imaging positron emission tomography pet computed tomography ct endoscopy es mammograms mg digital radiography dr phosphor plate radiography histopathology ophthalmology etc.additional types image formats always added.clinical areas beyond radiology cardiology oncology gastroenterology even laboratory creating medical images incorporated pacs.see dicom application areas.
Picture archiving and communication system	uses pacs four main useshard copy replacement pacs replaces hardcopy based means managing medical images film archives.decreasing price digital storage pacs provide growing cost space advantage film archives addition instant access prior images institution.digital copies referred softcopy.remote access expands possibilities conventional systems providing capabilities offsite viewing reporting distance education telediagnosis.enables practitioners different physical locations access information simultaneously teleradiology.electronic image integration platform pacs provides electronic platform radiology images interfacing medical automation systems hospital information system electronic medical record emr practice management software radiology information system ris.radiology workflow management pacs used radiology personnel manage workflow patient exams.pacs offered virtually major medical imaging equipment manufacturers medical companies many independent software companies.basic pacs software found free internet.
Picture archiving and communication system	architecture architecture physical implementation required functionality one sees outside.different views depending user.radiologist typically sees viewing station technologist qa workstation pacs administrator might spend time climatecontrolled computer room.composite view rather different various vendors.typically pacs consists multitude devices.first step typical pacs systems modality.
Picture archiving and communication system	modalities typically computed tomography ct ultrasound nuclear medicine positron emission tomography pet magnetic resonance imaging mri.depending facilitys workflow modalities send quality assurance qa workstation sometimes called pacs gateway.qa workstation checkpoint make sure patient demographics correct well important attributes study.study information correct images passed archive storage.central storage device archive stores images cases reports measurements information resides images.
Picture archiving and communication system	next step pacs workflow reading workstations.reading workstation radiologist reviews patients study formulates diagnosis.normally tied reading workstation reporting package assists radiologist dictating final report.reporting software optional various ways doctors prefer dictate report.ancillary workflow mentioned normally cddvd authoring software used burn patient studies distribution patients referring physicians.
Picture archiving and communication system	diagram shows typical workflow imaging centers hospitals.note section cover integration radiology information system hospital information system frontend system relates pacs workflow.more pacs include webbased interfaces utilize internet wide area network wan means communication usually via vpn virtual private network ssl secure sockets layer.clients side software may use activex javascript andor java applet.robust pacs clients full applications utilize full resources computer executing unaffected frequent unattended web browser java updates.need distribution images reports becomes widespread push pacs systems support dicom part dicom standard.
Picture archiving and communication system	web access dicom objects wado creates necessary standard expose images reports web truly portable medium.without stepping outside focus pacs architecture wado becomes solution cross platform capability increase distribution images reports referring physicians patients.pacs image backup critical sometimes overlooked part pacs architecture see below.hipaa requires backup copies patient images made case image loss pacs.several methods backing images typically involve automatically sending copies images separate computer storage preferably offsite.querying cfind image instance retrieval cmove cget communication pacs server done dicom messages similar dicom image headers different attributes.
Picture archiving and communication system	query cfind performed followsthe client establishes network connection pacs server.the client prepares cfind request message list dicom attributes.the client fills cfind request message keys matched.e.g.query patient id patient id attribute filled patients id.the client creates empty zero length attributes attributes wishes receive server.e.g.client wishes receive id use receive images see image retrieval include zerolength sopinstanceuid attribute cfind request messages.the cfind request message sent server.the server sends back client list cfind response messages also list dicom attributes populated values match.the client extracts attributes interest response messages objects.images composite instances like presentation states structured reports retrieved pacs server either cmove cget request using dicom network protocol.
Picture archiving and communication system	retrieval performed study series image instance level.cmove request specifies retrieved instances sent using separate cstore messages one separate connections identifier known destination application entity title ae title.cmove work server must configured mapping ae title tcpip address port consequence server must know advance ae titles ever requested send images to.cget hand performs cstore operations connection request hence require server know client tcpip address port hence also works easily firewalls network address translation environments incoming tcp cstore connections required cmove may get through.difference cmove cget somewhat analogous difference active passive ftp.
Picture archiving and communication system	cmove commonly used within enterprises facilities whereas cget practical enterprises.in addition traditional dicom network services particularly crossenterprise use dicom ihe define retrieval mechanisms including wado wadows recently wadors.image archival backup digital medical images typically stored locally pacs retrieval.important required united states security rules administrative safeguards section hipaa facilities means recovering images event error disaster.while facility different goal image backup make automatic easy administer possible.hope copies wont needed however disaster recovery business continuity planning dictates plans include maintaining copies data even entire site temporarily permanently lost.ideally copies images maintained several locations including offsite provide disaster recovery capabilities.general pacs data different business critical data protected multiple copies multiple locations.
Picture archiving and communication system	pacs data considered protected health information phi regulations may apply notably hipaa hipaa hitech requirements.images may stored locally remotely offline media disk tape optical media.use storage systems using modern data protection technologies become increasingly common particularly larger organizations greater capacity performance requirements.storage systems may configured attached pacs server various ways either directattached storage das networkattached storage nas via storage area network san.however storage attached enterprise storage systems commonly utilize raid technologies provide high availability fault tolerance protect failures.event necessary reconstruct pacs partially completely means rapidly transferring data back pacs required preferably pacs continues operate.modern data storage replication technologies may applied pacs information including creation local copies via pointintime copy locally protected copies along complete copies data separate repositories including disk tape based systems.
Picture archiving and communication system	remote copies data created either physically moving tapes offsite copying data remote storage systems.whenever hipaa protected data moved encrypted includes sending via physical tape replication technologies wan secondary location.other options creating copies pacs data include removable media hard drives dvds media hold many patients images physically transferred offsite.hipaa hitech mandates encryption stored data many instances security mechanisms avoid penalties failure comply.the backup infrastructure may also capable supporting migration images new pacs.due high volume images need archived many rad centers migrating systems cloudbased pacs.integration full pacs provide single point access images associated data.
Picture archiving and communication system	support digital modalities departments throughout enterprise.however pacs penetration complete individual islands digital imaging yet connected central pacs may exist.may take form localized modalityspecific network modalities workstations storage socalled minipacs may consist small cluster modalities directly connected reading workstations without long term storage management.systems also often connected departmental information system.historically ultrasound nuclear medicine cardiology cath labs often departments adopt approach.more recently full field digital mammography ffdm taken similar approach largely large image size highly specialized reading workflow display requirements intervention regulators.rapid deployment ffdm us following dmist study led integration digital mammography pacs becoming commonplace.all pacs whether span entire enterprise localized within department also interface existing hospital information systems hospital information system radiology information system ris.there several data flowing pacs inputs next procedures back results corresponding inputsin patient identification orders examination.
Picture archiving and communication system	data sent ris via integration interface hospital via hl protocol.patient id orders sent modality ctmretc via dicom protocol worklist.images created images scanning forwarded pacs server.diagnosis report created based images retrieved presenting pacs server physicianradiologist saved ris system.out diagnosis report images created accordingly.diagnosis report sent back via hl usually images sent back via dicom usually dicom viewer integrated hospitals cases clinical physician gets reminder diagnosis report coming queries images pacs server.interfacing multiple systems provides consistent reliable datasetless risk entering incorrect patient id study – modalities support dicom worklists retrieve identifying patient information patient name patient number accession number upcoming cases present technologist preventing data entry errors acquisition.
Picture archiving and communication system	acquisition complete pacs compare embedded image data list scheduled studies ris flag warning image data match scheduled study.data saved pacs tagged unique patient identifiers social security number nhs number obtained his.providing robust method merging datasets multiple hospitals even different centers use different id systems internally.an interface also improve workflow patternswhen study reported radiologist pacs mark read.avoids needless doublereading.report attached images viewable via single interface.improved use online storage nearline storage image archive.pacs obtain lists appointments admissions advance allowing images prefetched offline storage nearline storage onto online disk storage.recognition importance integration led number suppliers develop fully integrated rispacs.
Picture archiving and communication system	may offer number advanced featuresdictation reports integrated single system.integrated speechtotext voice recognition software may used create upload report patients chart within minutes patients scan reporting physician may dictate findings phone system voice recorder.recording may automatically sent transcript writers workstation typing also made available access physicians avoiding typing delays urgent results retained case typing error.provides single tool quality control audit purposes.rejected images tagged allowing later analysis may required radiation protection legislation.workloads turnaround time reported automatically management purposes.
Picture archiving and communication system	acceptance testing pacs installation process complicated requiring time resources planning testing.installation complete acceptance test passed.acceptance testing new installation vital step assure user compliance functionality especially clinical safety.take example therac radiation medical device involved accidents patients given massive overdoses radiation due unverified software control.the acceptance test determines whether pacs ready clinical use marks warranty timeline serving payment milestone.test process varies time requirements depending facility size contract condition day time limit unusual.
Picture archiving and communication system	requires detailed planning development testing criteria prior writing contract.joint process requiring defined test protocols benchmarks.testing uncovers deficiencies.study determined frequently cited deficiencies costly components.failures ranked mosttoleast common workstation hisrisacs broker interfaces ris computer monitors webbased image distribution system modality interfaces archive devices maintenance training network dicom teleradiology security film digitizer.history one first basic pacs created dr richard j. steckel.the principles pacs first discussed meetings radiologists .
Picture archiving and communication system	various people credited coinage term pacs.cardiovascular radiologist dr andre duerinckx reported first used term .dr samuel dwyer though credits dr judith m. prewitt introducing term.dr harold glass medical physicist working london early secured uk government funding managed project many years transformed hammersmith hospital london first filmless hospital united kingdom.dr glass died months project came live credited one pioneers pacs.the first largescale pacs installation university kansas kansas city.first installation became teaching experience rather pacs installation.
Picture archiving and communication system	regulatory concerns us pacs classified medical devices hence sale regulated usfda.general subject class controls hence require k though individual pacs components may subject less stringent general controls.specific applications use primary mammography interpretation additionally regulated within scope mammography quality standards act.the society imaging informatics medicine siim worldwide professional trade organization provides annual meeting peerreviewed journal promote research education pacs related digital topics.see also references citations sources huang h. k. .pacs imaging informatics basic principles applications.
PartitionMagic	new jersey john wiley sons.isbn .external links pacs history web siteusc ipilab research article backupdecember symantec website stated longer offer partition magic.program runs prevista microsoft windows operating systems including windows windows xp application incompatible windows vista later versions although microsoft added resizing.cases existing partitions resized without loss data.details partitionmagic capable resizing ntfs fat fat partitions without data loss copy move partitions including disks.also various features including able convert fat fat ntfs modify cluster size fat fat ntfs filesystems merge adjacent fat ntfs filesystems without data loss though ntfsonly metadata lost conversion fat.
PartitionMagic	additionally somewhat limited support ext ext partitions.partitionmagic first commercial product kind containing patented technology.the first version partitionmagic released dos os support.versions – offered dos os windows support.symantecs partitionmagic version dropped os version.server versions also offered name server magic windows novell netware servers.the stable version partitionmagic .
PartitionMagic	also included rescue floppy disk additional dos version partitionmagic.dos version included drdos msdos came one .mb two .mb floppy disks.the windows version partitionmagic could also integrated bartpe barts preinstalled environment windows xp based live cd created using pe builder.integrate partitionmagic bartpe pe builder plugin partitionmagic available.
PartitionMagic	history powerquests partition magic originated version .available purchase january .os version available september .version .came early .partitionmagic powerquest updated regularly adding new features.symantec purchased application new releases symantec stated plans releasing new version.
PartitionMagic	october symantec website stated sorry longer offer norton partition magic.competition product named partition commander vcom products partition magics competitor.also paragon partition manager compatibility issues partitionmagic compatible windows nt xp desktop editions.however compatible server editions windows nt design – expensive product manufacturer servermagic would handle – run windows vista later versions.partitionmagic .. volumemanager volumemanager cannot resize dynamic disks.see also disk partitioninglist disk partitioning softwarentfsresizeresizefs references external links download partition magic demo softpedia
Tax withholding in the United States	withholding tax wages includes income tax social security medicare taxes states.certain minimum amounts wage income subject income tax withholding.wage withholding based wages actually paid employee declarations federal state forms w. social security tax withholding terminates payments one employer exceed maximum wage base year.amounts withheld payers employers others must remitted relevant government promptly.amounts subject withholding taxes withheld reported payees government annually.history world war ii congress introduced payroll withholding quarterly tax payments vote current tax payment act history u.s. tax system u.s. department treasury describes tax withholding.this greatly eased collection tax taxpayer bureau internal revenue.
Tax withholding in the United States	however also greatly reduced taxpayers awareness amount tax collected i.e.reduced transparency tax made easier raise taxes future.withholding wages us withholding employers tax wages required federal state local governments.taxes withheld include federal income tax social security medicare taxes state income tax certain levies states.income tax withheld wages based amount wages less amount declared withholding allowances often called exemptions.withholding allowances calculated based assumption full year wages.
Tax withholding in the United States	amounts tax withheld determined employer.tax rates withholding tables apply separately federal state local levels.amount withheld based amount wages paid paycheck period covered paycheck.federal state withholding amounts graduated rates higher wages higher withholding percentages.withheld income taxes treated employees payment account tax due year determined annual income tax return filed end year federal form series appropriate state forms.
Tax withholding in the United States	withholdings excess tax determined refunded.under internal revenue code section f related u.s. treasury regulations employee must provide employer federal form w employees withholding allowance certificate.states accept w form similar form especially employee filing different information state level federal employee may paying different amount withholding claiming different number exemptions state level federal level.form provides employer social security number.also form employees declare number withholding allowances believe entitled to.allowances generally based number personal exemptions plus amount itemized deductions losses credits.
Tax withholding in the United States	employers entitled rely employee declarations form w unless know wrong.social security tax withheld wages flat rate ...wages paid fixed amount year one employee subject social security tax.wage maximum .
Tax withholding in the United States	medicare tax .withheld wages maximum.brings total federal payroll tax withholding .. employers required pay additional equal amount medicare taxes .rate social security taxes.many states also impose additional taxes withheld wages.wages defined somewhat differently different withholding tax purposes.thus federal income tax wages may differ social security wages may differ state wages.
Tax withholding in the United States	withholding payments foreign persons companies individuals make certain types payments foreign persons must withhold federal income tax payments.foreign persons include nonresident aliens foreign corporations foreign partnerships.payments subject withholding include compensation services interest dividends rents royalties annuities certain payments.tax withheld gross amount payment.withholding rate may reduced tax treaty.
Tax withholding in the United States	tax withheld usually considered final determination payment tax requiring action tax return foreign person.in addition partnerships required make tax payments referred withholding behalf foreign partners.payments required regardless whether income actually distributed partner.payments also required quarterly year end business income undistributed income.partnership payments business income treated like estimated tax payments foreign person must still file u.s. tax return reporting business income.purchasers u.s. real estate must withhold sales price payments foreign sellers.amount reduced anticipated federal income tax due upon advance application form b internal revenue service.
Tax withholding in the United States	payments treated like estimated tax payments foreign person must still file u.s. tax return reporting gain loss.backup withholding payers interest dividends certain items must withhold federal income tax payments limited circumstances.generally applies recipient u.s. person eitherthe person failed provide tax identification number form w payer orthe internal revenue service irs notified payer payer must withhold.payment withheld taxes withheld taxes must paid appropriate government promptly.rules vary jurisdiction balance total payments due.
Tax withholding in the United States	federal employment tax payments due either monthly semiweekly.federal tax payments must made either deposit national bank electronic funds transfer.balance federal tax payments exceeds must paid within one banking day.beginning january payments may made electronic funds transfer.state rules vary widely generally allow slightly time deposit withheld taxes.
Tax withholding in the United States	reporting withheld taxes employers must file quarterly report aggregate withholding taxes form internal revenue service.report includes income social security medicare tax totals quarter.partnerships making payments partners must file form quarterly.state requirements vary.all persons withholding taxes must file annual federal state reports tax withheld amount subject withholding.copy must provided employee payee.
Tax withholding in the United States	relevant forms followsform w series wages federal report also used states due employees january .summary filed form w.form payments foreign persons due payees march .summary filed form .form partnership payments due time partnership return.summary filed form .form series backup withholdingfederal filings must done electronically forms required.states generally require separate filings partnerships instead relying information provided irs.
Tax withholding in the United States	penalties failing pay federal taxes withheld result penalty amount paid.may assessed anyone responsible funds payment withheld tax could made.paying withheld federal taxes late may result penalties plus interest balance paid late.state penalties vary.failure timely file withholding tax forms may result penalties per form filed.intentional failures may result criminal penalties.see also income tax united statesirs penaltiesmedicare united statessocial security united statesunited states v. gotcher notes references

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