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International Journal of Scientific Engineering and Research IJSERww International Journal of Scientific Engineering and Research IJSERww

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ISSN Online Volume 2 Issue November Licensed Under Creative Commons Attribution CC BY 7Jian L andLiganStudyChaoticCryptosystemforDigitalImageTripleDataEncryptionAlgorithmModesOperationANSIX95 ID: 947197

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International Journal of Scientific Engineering and Research (IJSER)www.ijser.in ISSN (Online): Volume 2 Issue , November Licensed Under Creative Commons Attribution CC BY [7]Jian L andLiganStudyChaoticCryptosystemforDigitalImageTripleDataEncryptionAlgorithmModesOperation,ANSIX9.52 - [8]TripleDataEncryptionAlgorithmModesOperation,ANSIX9.52 - AuthorProfileMr.KarthikreceivedtheM.C.A,SacredHeartCollege,Tirupattur,andpursuingM.Phil.,degreeDonBoscoCollege,Sogathur,Dharmapuri,Tamilnadu,India. a ResearchScholarthefieldNetworkSecurity. verymuchenthusiasticNETWORKINGarea.Mr.MuruanandamreceivedtheM.Sc.,ThanthaiHansRoeverCollege, Perambalur,andM.Phil.,degreeManonmaniamSundaranarUniversity,Tirunelveli,Tamilnadu, in andrespectively.AssistantProfessorcumHeadtheResearchDepartmentComputerScience,DonBoscoCollege,Sogathur,Dharmapuri,Tamilnadu,India.PresentlypursuingDoctorateDegree[Ph.D.]ComputerScienceBharathiarUniversity,Coimbatore. a ResearchScholarthefieldWirelessSensorNetworks. verymuchinterestedNetworkingarea.. Hisongoingresearchfocused SelectiveJammingAttacksWirelessSensoretwork International Journal of Scientific Engineering and Research (IJSER)www.ijser.in ISSN (Online): Volume 2 Issue , November Licensed Under Creative Commons Attribution CC BY Figure 5: EnvironmentSimulationProgram5.1.2SimulationResultsThissectionshowtheresultsobtainedfromrunningthesimulationprogramusingdifferentdataloads.TheresushowtheimpactchangingdataloadalgorithmandtheimpactCipherMode(EncryptionMode)used. 5.1.3PerformanceResultswithECBThefirstsetexperimentswereconductedusingECBmode,theresultsareshownbelowFigure 5.2.TheresultsshowthesuperiorityDESalgorithmoverotheralgorithmstermstheprocessingtime.showsalsothatAESconsumesmoreresourceswhenthedatablocksizerelativelybig.Theresultsshownherearedifferentfromtheresults, since thedatablocksizesusedherearemuchlargerthantheonesusedtheirexperiment.Note:here3DESrequiresalwaysmoretimethanDESbecausetriplephaseencryptioncharacteristic.DESand3DESareknownhavewormholestheirsecurity mechanism,BlowfishandAES,theotherhand,nothaveanyfar.Theseresultshavenothingwiththeotherloadsthecomputersincesingleexperimentwasconductedmultipletimesresultingalmostthesameexpectedresult.DES,3DES aAESimplementation.NETbest. Figure5.2:PerformanceResultswithECBMode5.1.4PerformanceResultswithCBC CBCrequiresmoreprocessingtimethanECBbecaukeychainingnature.TheresultsshowFigure 5indicates alsothattheextratimeaddednotsignificantformanyapplications,knowingthatCBCmuchbetterthanECBtermsprotection.ThedifferencebetweenthetwomodeshardthentheresultsshowedthattheaveragedifferencebetweenECBandCBC0.059896seconds, whichrelativelysmall. Figure 5.3: PerformanceResultswithCBCModeThissectionshowedthesimulationresultsobtainedrunningthefourcomparedencryptionalgorithmsusingdifferentCipherModes.Differentloadhave

been useddeterminetheprocessingpowerandperformancethecomparedalgorithm.Conclusion and Futurework Thepresentedsimulationresultsshowedthat3DEShas a betterperformanceresultwithECBandCBCthanothercommonencryptionalgorithmsused. In thispaperpresenta performanceevaluationselectedsymmetricencryptionalgorithms.TheselectedalgorithmsareAES,DES,3DES,Blowfish,, and4. casechangingkeysize,seenthathigherkeysizeleadsclearchangethebatteryandtimeconsumption.futuretheworkmayextensiveincludingtheschemesandtechniquesoverdifferenttypesdatasuchimage,soundandvideoandrising a strongerencryptionalgorithmwithhighspeedandminimumenergyconsumption. Acknowledgement My sinceregratitudeTheManagement,and I gratefulthankourdepartmentstaffmemberscomputerscience,DonBoscoCollege,Dharmapuri,TamilNadu,India,fortheirSupportandmotivation.References [1]AamerNadeem,PerformanceComparisonDataEncryptionAlgorithm,”IEEE [2]Abdulkader,DiaasalamaandMohivHadhoud,“StudyingtheEffectMostCommonEncryptionAlgorithms,”InternationalArabJournal e-technology,Vol.2.No.1.[3]AmanKumar,SudeshJakhar,nilMaakar,“DistinctionbetweenSecretkeyandPublickeyCryptographywithexistingGlitches”,Volume: [4]DataEncryptionStandard(DES),FIPSPUB-3 - [5]Feistel,CryptographyandComputerPrivacy,ScientificAmerican,Volume:No.5,[6]GrabbeJ,DataEncryptionStandard:TheTripleDESalgorithmillustratedLaissezfairecitytime,Volume:No.and International Journal of Scientific Engineering and Research (IJSER)www.ijser.in ISSN (Online): Volume 2 Issue , November Licensed Under Creative Commons Attribution CC BY Figure4.4: ComparativeExecutiontimeEncryptionAlgorithmSystem 2 TheresulteasyobservethatBlowfishhasvantageoverotheralgorithmstermsthroughputandalsocomparisonbetweenthealgorithmsstreammodeusingChainBlockChaining (CBC). TheresultsshowedthatBlowfishhas a verygoodperformancecomparedotheralgorithms.AlsoshowedthatAEShas a betterperformancethan3DESandDES.Amazinglyshowsalsothat3DEShasalmost1/3throughputDES,otherwordsneeds 3 timesthanDESprocessthesameamountdata. Theaboveexperimentsforcomparingtheperformancee differentencryptionalgorithmsimplementedinside.NETframework.TheirresultsareclosetheonesshownFigure4.3. Figure: Comparisonresultsusing.NETimplementations.Thecomparisonwasperformedthefollowingalgorithms:DES,Triple DES(3DES),andAES(Rijndael).TheresultsshowsthatAESoutperformedotheralgorithmsboththenumberrequestsprocessesperseconddifferentuserloads,andtheresponsetimedifferentuserloadsituations. SimulationEnvironment and DiscussionThissimulationusestheprovidedclasses.NETenvironmentsimulatetheperformanceDES,3DESandAES(Rijndael).thisTripleDataEncryptionStandardimplementationusedhereunderthenameCryptograph.NET.Thisimplementation thoroughlytestedandoptimizedgivethemaximumperformanceforthealgorithm.TheimplementationusesmanagedwrappersforDES,3

DESandRijndaelavailableSystem.Security.CryptographythatwrapsunmanagedimplementationsavailableCryptoAPI.TDESCryptoServiceProvider, TripleDESCryptoServiceProvrandRijndaelManagedrespectivelThereonly a puremanagedimplementationRijndaelavailableSystem.Security.Cryptography,whichwasusedthetests.5.1PerformanceEvaluationMethodologyThissectiondescribesthetechniquesandsimulationchoicesmadeevaluatetheperformancethecomparedalgorithms.additionthat,willdiscussthemethodologyrelatedparameterslike:systemparameters,experimentfactor(s),andexperimentinitialsettings.5.1.1SimulationProcedure Considerthedifferentsizesdatablocks(0.5MB20MB)thealgorithmswereevaluatedtermsthetimerequiredencryptanddecryptthedatablock.AlltheimplementationswereexactmakesuretheaccurateresultsTheSimulationogramacceptsthreeinputs: Algorithm, CipherModeand Datablocksize. After a successfulexecution,thedatagenerated,encrypted,anddecryptedareshowntheFigure 5.1.Note:Mostthecharacterscannotappearsincetheynothavecharacterrepresentation.Anothercomparisonmadeafterthesuccessfulencryption/decryptionprocessmakesurethatallthedataareprocessedtherightwaycomparingthegenerateddata(theoriginalblocks)andthedecrypteddatablockgeneratedfromtheprocess. International Journal of Scientific Engineering and Research (IJSER)www.ijser.in ISSN (Online): Volume 2 Issue , November Licensed Under Creative Commons Attribution CC BY Figure3.5: BlockDiagrams:3DESecryptionPerformance Analysis of DataEncryptionAlgorithms thisareaintendsgivethereadersforthenecessaryackgroundunderstandthekeydifferencesbetweenthecomparedalgorithms.DES:(DataEncryptionStandard),wasthefirstencryptionstandardrecommendedNIST(NationalInstituteStandardsandTechnology).basedtheIBMproposedalgorithmcalledLucifer.DESbecame a standardSincethattime,manyattacksandmethodsrecordedthatexploittheweaknessesDES,whichmadeinsecureblockcipher.3DES:enhancementDES,the3DES(TripleDES)encryptionstandardwasproposed.thisstandardtheencryptionmethodsimilartheoneoriginalDESbutapplied 3 timesincreasetheencryptionlevel. AES:(AdvancedEncryptionStandard),thenewencryptionstandardrecommendedNISTreplaceDES.Rijndael (pronouncedRainDoll)algorithmwasselected, after a competitionselectthebestencryptionstandard.Bruteforceattacktheonlyeffectiveattackknownagainstwhichtheattackertriestestallthecharacterscombinationsunlock theencryption.BothAESandDESareblockciphers.lowfish:lowfish a variablelengthkey,bitblockcipher.TheBlowfishalgorithmwasfirstintroducedThisalgorithmoptimizedhardwareapplicationsthoughit'smostlyusedsoftwareapplications.suffersfromweakkeysproblem,attackknownsuccessfulagainst.4.1Related Work andComparativeResults Togivemoreprospectiveabouttheperformancethecomparedalgorithms,thissectiondiscussestheresulobtainedfromherresources.ThebelowTable 4containsthespeedbenchmarksforsomethemostcommonlyusedcry

ptographicalgorithms.Theseresultsaregoodhaveindicationaboutwhatthepresentedcomparisonresults.shownthatBlowfishandAEShavethebestperformanceamongothers.Andboththemareknownhavebetterencryption(i.e.strongeragainstdataattacks)thantheothertwo. Table 4ComparisonresultsusingCrypto++Algorithm Megabytes(2^20 bytes)Processed TimeTakenMB/Second Blowfish3.97664.386 Rijndael(128bitkey) 4.19661.01 Rijndael(192bitkey) 4.81753.145 Rijndael(256bitkey) 5.30848.229 DES5.99821.34 (3DES)DESXEX36.15920.783 (3DES)DESEDE36.4999.848 Figure4.2: ComparisonresultsusingCrypto++ - Graph Figure4.3: ComparativeExecutiontimeEncryptionAlgorithmSystem 1 International Journal of Scientific Engineering and Research (IJSER)www.ijser.in ISSN (Online): Volume 2 Issue , November Licensed Under Creative Commons Attribution CC BY Theleastsignificant(rightmost)bitbyte a paritybit,andshouldsetthattherearealwaysnumbereverybyte.Theseparitybitsareignored,onlythesevenmostsignificantbitsbyteareused,resultinga keylengthbits.ThismeansthattheeffectivekeystrengthforTripleDESactuallybitsbecausethethreekeyscontains 8 paritybitsthatarenotusedduringtheencryptionprocess. ure3.2: TripleDESUsingbytesTheaboveFigure 3.2 shownTripleDataEncryptionStandard(DES) a typecomputerizedcryptographywhereblockcipheralgorithmsareappliedthreetimesdatablock.ThekeysizeincreasedTriple DESensureadditionalsecuritythroughencryptioncapabilities.Eachblockcontainsbitsdata.Threekeysarereferredbundlekeyswithbitsperkey.Therearethreekeyingoptionsdataencryptionstandards:AllkeysbeingindependeKey 1 andkey 2 beingindependentkeysAllthreekeysbeingidenticalKeyoption 3 shownFigure 3.3:triplesDES.ThetripleDESkeylengthcontainsbitsbutthekeysecurityfallsbits Figure3.3: WorkingTripleDES(i)Algorithm: RunDESthreetimes:ECBmode: K = K, thisDESBackwardscompatibilityKnownnotjustDESwith K Hasbitssecurity,not 3 = TripleDESalgorithmusesthreeiterationscommonDEScipher. It receives a secretbitkey,whichdividedintothreebitkeys.EncryptionusingthefirstsecretkeyDecryptionusingthesecondsecretkeyEncryptionusingthethirdsecretkeyEncryption: c = E3(D2(E1(m)))Decryption: m = (E2(D3(c)))UsingdecryptionthesecondstepduringencryptionprovidesbackwardcompatibilitywithcommonDESalgorithm.thesecasefirstandsecondsecretkeyssecondandthirdsecretkeysarethesamewhicheverkey.c = E3 (D1(E1(m))) = E3(m) c = E3(D3(E1(m))) = E1(m)possibleuse3DEScipherwith a secretbitkey.thiscasefirstandthirdsecretkeysarethesame. c = E(m)))TripleDESadvantageousbecausehas a significantlyizedkeylength,whichlongerthanmostkeylengthsaffiliatedwithotherencryptionmodes.DESalgorithmwasreplacedtheAdvancedEncryptionStandardandTripleDESnowconsideredobsolete.derivesfromsingleDESbutthetechnique usedtriplicateandinvolvesthreesubkeysandkeypaddingwhennecessary.KeysmustincreasedbitslengthKnownforcompatibilityandflexibilityea

silyconvertedforTripleDESinclusion.ThefollowingFigure3.4andFigure3.5theblockiagramDESshownbelow. Figure3.4: BlockDiagrams:3DESEncryption International Journal of Scientific Engineering and Research (IJSER)www.ijser.in ISSN (Online): Volume 2 Issue , November Licensed Under Creative Commons Attribution CC BY 2.1.1ManualEncryptionManualencryption a typethatinvolvestheuseencryptionsoftware.Thesearecomputerprogramsthatencryptvariousbitsinformationdigitally.Manualencryptioninvolvestheuser'sparticipationcompletely.Thefileswantsencryptarechosen,andthenencryptiontypechosenfrom a listthatthesecuritysystemprovides. 2.1.2TransparentEncryptionTransparentencryptionanothertypecomputersoftwareencryption.downloaded onto a computercrypteverythingautomatically. Othemostimportantsecuretypesencryptionavailablebecausedoesn'tleaveanythingthatmightforgottenwhenusingmanualencryption.Everyexecutableapplicationandfilecreatedthecomputerhasencryptedcopythatwithstandpowersurgesandprotectsinformationcase a computerstolen.2.1.3SymmetricEncryptionAllencryptiondonevia a computersoftwareprogram.Youeasilyencryptinformationyourself.One of thesimplestwaysthisthroughsymmetricencryption.Here, a letternumbercoincideswithanotherletternumbertheencryptioncode.Youtakeanywrittentextandsubstitutelettersandnumbersfortheircodedcounterpart,thusencryptingthetext.2.1.4symmetricncryptionAsymmetricencryption a secureandeasywaythatusedencryptdatathatyouwillreceiving.generallydoneelectronically. A publickeygivenoutwhomeveryouwantpostedsomewhere forthepublicsee.Theyencryptinformationusingthekeyandsendyou.Thisoftendonewhenwritingemails.Thismeansencryptthedatawiththepublickey,onlyreadagainwhomevertheprivatekeyhas.2.2TypesDecryption2.2.1Symmetriccryptionsymmetricencryption,thesamemathematicalequationbothencryptsanddecryptsthedata.Thefollowingexample,a simplelettersubstitutioncipher,suchA=B,B=C,etc.,symmetricalbecauseyousimplyreversetheprocessdecryptthemessage.yousend a messageusing a symmetricencryptionmethod,therecipientsmustalsohavethekeydecryptthedocument.2.2.2AsymmetricDecryptionAsymmetricdecryptionmethods,alsoknownpublickeydecryption, use a systeminvolving a pairlinkedkeys.thissystem,anythingencodedwithonekeyrequirestheotherkeydecrypt,andon.Whenyouencode a messageusingsomeone’spublickey,youknowthatonly a recipientpossessingthecorrespondingprivate kread HashingHashing a formencryptionthatuses a specializedonewayencryptionkey.youhash a givenvolumedata,willproduce a uniqueoutputstringthatdata,butimpossiblereconstructthedatafromthe outputstring.YouencodetheoriginaldataandcomparetheresultstringverifyThisserve a typeerrorcorrectionencoding.Hashing a messageandprovidingthatvalueyourcorrespondentsensuresthattheyhashthe messagethemselvesandcomparethevalues.longthetwooutputstringsmatch,recipientsknowthemessagecompletea

ndunaltered.Cryptographic 3.1SymmetricKeyCryptography TheDESmostwidelyusedsymmetrickeycryptographicmethod tDataEncryptionStandard (DES)shownbelowFigure3.1: uses a fixedlength,bitkeyandefficientalgorithmquicklyencryptanddecryptmessages.easilyimplementedtheencryptionanddecryptionprocessevenfaster.general,increasingthekeysizemakesthesystemmoresecure. A variationDES,calledTripleDESDES - EDE(EncryptDecrypt-Encrypt),usesthreeapplicationsDESandtwoindependentDESkeysproduceeffectivekeylengthbits. Figure3.1: SymmetricKey – TripleDESDespitetheefficiencysymmetrickeycryptography,has a fundamentalweakspotkeyTheInternationalDataEncryptionAlgorithm(IDEA)wasinventedJamesMasseyIDEAuses a fixedlength,bitkey(largerthanDESbutsmallerthanTripleDES).alsofasterthanTripleDES.theearly1990s,DonRivestRSADataSecurity,Inc.,inventedthealgorithmsandRC4.TheseusevariablelengthkeysandareclaimedevenfasterthanIDEA. 3.2plementationTripleDES(3DES) a standardANSX9.52andnamedTripleDataEncryptionAlgorithm(TDEA).BlockcipherwithsymmetricsecretkeyBlocklength = bitsKeylength = bits3DESwascreatedbecauseDESalgorithm,inventedtheearlyusingbitkey.Theeffectivesecurity3DESprovidesonlybitsduemeetthemiddleattacks. TripleDESrunsthreetimesslowerthanDES,butmoresecureusedproperly.Theprocedurefordecryptingsomethingthesametheprocedureforencryption,exceptexecutedreverse.DES,dataencryptedanddecrypted -bitchunks.TheinputkeyforDESbitslong;theualkeyusedDESonlybitslength. International Journal of Scientific Engineering and Research (IJSER)www.ijser.in ISSN (Online): Volume 2 Issue , November Licensed Under Creative Commons Attribution CC BY Thesefunctionsareusuallyreferredthegoalsthesecuritysystem.Thesegoalsstedunderthefollowingfivemaincategories: Authentication:Authenticationmeansbeforesendingandreceivingdatausingthesystem,thereceiverandsenderidentityshouldverified. SecrecyConfidentiality:thisfunctionhowmostpeopleidentify a securesystem.meansonlytheauthenticatedpeopleareableinterpretthemessagecontentandoneelse. Integrity:Integrity meansthatthecontentthecommunicateddataassuredfreefromanytypemodificationbetweentheendpoints(senderandreceiver).ThebasicformintegritypacketchecksumIPv4packets. NonRepudiation:thisfunctionimpliesthatneitherthesendernorthereceiverfalselydenythattheyhavesenta certainmessage. ServiceReliabilityandAvailability:Sincesecuresystemsusuallygetattackedintruders,whichmayaffecttheiravailabilityandtypeservicetheirusers. 1.2.2Advantages DEShasbeenaround a longtime(since1977),evenrealweaknesseshavebeenfound: themostefficientattackstillbruteforce.fficialUnitedStatesGovernmentstandard;theGovernmentrequiredcertify,DESeveryfiveyearsandaskreplacednecessary.DEShasbeencertifiedandESalsoANSIandISOstandard. SinceDESwasdesignedrunhardware,fasthardwareandrelativelyfastsoftware1.2.3DisadvantagesThebitkeysizee bigges

tdefectDESandthechipsperformonemillionDESencryptdecryptoperations a secondareavailable(in1993). HardwareimplementationsDESareveryfast.DESwasnotdesignedforsoftwareandhencerunsrelativelyslowly.iv. a newtechnologyimproving a lotpossibilitybreaktheencryptedcode,AESpreferredthanDES.1.2.4ObjectivesProvidefunctionalitystore a fileencryptedformatwhichonlyaccessedprovidingthecorrectpassword.Modifythesystemmakethedirectoriespasswordprotected.Toreview a shorthistoryDESanddefinethebasicstructures.iv.escribethebuildingblockelementsDESTodescribetheroundkeysgenerationprocessandanalyzedataencryptionstandard.1.2.5Motivation(a)SecuritySecuresdatafrombeingaccessedanymalicioususer.(b)PrivacyEnsurethatprivatedatanotaccessedotherusers.(c)ReliabilityOnlyresponsibleusersareprovidedaccessthesedata.ResourcesharingManyusersusethesamesystemandstillworkindependently1.3AES(AdvancedEncryptionStandard) AES a newcryptographicalgorithmthatusedprotectelectronicdata.Specifically,AESiterative,symmetrickeyblockcipherthatusekeysandbits,andencryptsanddecryptsdatablocksbits(16bytes). A Publickeyciphers,use a pairkeys,symmetrickeyciphersusethesamekeyencryptanddecryptdata.ThenewAESwillcertainlybecomethefactostandardforencryptingallformselectronicinformation,replacingDES.AESencrypteddataunbreakablethesensethatknowncryptanalysisattackdecrypttheAESciphertextwithoutusing a bruteforcesearchthroughallpossiblebitkeys.Securitylongerafterthoughtanyone'ssoftware designanddevelopmentprocess. It willgreatlyincreasethereliabilityandsafetyyoursoftwaresystems.DES a blockcipher,shownbelowFigure1.3. Figure 1.3: EncryptionanddecryptionwithDESOverview of Encryption and DecryptionEncryption a processcodinginformationwhichcouldeither a filemailmessageintociphertext a formunreadablewithout a decodingkeyorderpreventanyoneexcepttheintendedrecipientfromreadingthatdata.Decryptionthereverseprocessconvertingencodeddataoriginencodedform,plaintext. A keycryptography a longsequencebitsusedencryption / decryptionalgorithms.Thefollowingexamplerepresents a hypotheticalbitkey: 2.1TypesEncryptionDependingthetypeencryption,informationdisplayedvariousnumbers,letters,symbols.Thosewhoworkcryptographyfieldsmaketheirjob, encryptinformationbreakcodesreceiveencryptedinformation. International Journal of Scientific Engineering and Research (IJSER)www.ijser.in ISSN (Online): Volume 2 Issue , November Licensed Under Creative Commons Attribution CC BY Encryption and Decryption by UsingTriple and Performance Analysis of Crypto SystemKarthik .MuruganandamResearchScholar,PeriyarUniversity,Salem, Tamilnadu, IndiaResearchScholar,BharathiarUniversity,Coimbatore, Tamilnadu, IndiaAbstractThispapercontains a technique for secretcommunicationusingcryptography. a techniquewhichusedprotecttheimportantdata.Thesecretmessageencrypted a blockcipherbased two

cryptographicalgorithms, theDataEncryptionStandard(DES) andtheTripleDataEncryptionAlgorithm (TDEA) whichmayusedFederalorganizationsprotect sensitivedata.Thisalgorithmuniquelydefinesthemathematicalstepsrequiredtransformdatainto a cryptographiccipherd alsotransforms thecipherbacktheoriginalformwithblocklengthbitsandkeylengthbits. Thispaperprovides a performancecomparisonbetweenthe mostcommonencryptionalgorithmsDES,3DES, AES and Blowfish. Keywords: DES,TripleDES,AES, CryptographyIntroductionDataEncryptionStandard(DES)theblockcipherwhichtakes a fixedlengthstringplaintextbitsandtransformsthrough a seriescomplicatedoperationsintoanotherciphertextbitstringthesamength. a symmetricencryptiontechniquewhichmeansbothsenderandreceiveruse a sharedkeyencryptand/ordecryptthe datashownthebelowFigure1.1: Theproblemthistechniquethatthekeyknownotherstheentireconversationcompromised.The3DESblocksizebitsandalsouses a keycustomizethetransformation, so thatdecryptiononlyperformedthosewhoknowtheparticularkeyusedencrypt.Thekeybasicallyconsistsbitshowever,onlytheseareactuallyusedthealgorithm.Eightbitsareusedsolelyforcheckingparity,andthereafterdiscarded.Hencetheeffectivelengthbits”d alwaysquoted.Every 8bittheselectedkeydiscardedi.e.,positionsareremovedfromthebitkeyleavingbehindonlythebitkey. Figure1.1: ConversionSecretkey1.1History of DESDESalgorithmusedforencryptiontheelectronicdata.wasdevelopedtheearlyIBMandbasedearlierdesignHorstFeistel, thealgorithmsubmittedtheNationalBureauStandards(NBS)propose a candidatefortheprotectionsensitiveunclassifiedelectronicgovernmentdata.nowtakenunsecuredcausesmallsizeand a bruteforceattackpossibleJanuarydistributed.netandtheElectronicFrontierFoundation(EFF)collaboratedpubliclybreak a DESkeyhoursandminutes.ThealgorithmbelievedpracticallysecuretheformTripleDES,althoughtherearetheoreticalattacks.recentyears,thecipherhasbeensupersededtheAdvancedEncryptionStandard(AES).1.2Cryptography Cryptograpmeansdatasecure, it helpsensuredataprivacy,maintaindataintegrity,authenticatecommunicatingparties,andpreventrepudiation. Figure1.2: KeyschedulesforEncryptionandDecryptionTheaboveFigure1.2: shownkeyscheduleforencryptionanddecryptionalgorithmwhichgeneratesthesubkeys.Initially,bitsthekeyareselectedfromtheinitialPermutedChoice 1 (PCandtheremainingeightbitsareeitherdiscardedusedparitycheckbits.Thebitsaredividedintotwobithalves;halftreatedseparately.successiverounds,bothhalvesarerotatedleftoneandtwobits(specifiedforround),andthensubkeybitsareselectedPermutedChoice 2 (PCi.e.bitsfromthelefthalfandfromtheright.Therotations(denoted“”)meanthat a differentsetbitsusedsubkey,bitusedapproximatelyoutthesubkeys. 1.2.1CryptographyGoalsThissectionexplains thefivemaingoalshindusingCryptography.Everysecuritysystemmustprovide a bundlesecurityfunctionsthatassurethesecrecythesys