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首页 密码编码学与网络安全:原理与实践+第四版习题解答

密码编码学与网络安全:原理与实践+第四版习题解答.pdf

密码编码学与网络安全:原理与实践+第四版习题解答

eyoung
2011-03-08 0人阅读 举报 0 0 暂无简介

简介:本文档为《密码编码学与网络安全:原理与实践+第四版习题解答pdf》,可适用于高等教育领域

SOLUTIONSMANUALCRYPTOGRAPHYANDNETWORKSECURITYPRINCIPLESANDPRACTICEFOURTHEDITIONWILLIAMSTALLINGSCopyright:WilliamStallings©byWilliamStallingsAllrightsreservedNopartofthisdocumentmaybereproduced,inanyformorbyanymeans,orpostedontheInternet,withoutpermissioninwritingfromtheauthorNOTICEThismanualcontainssolutionstoallofthereviewquestionsandhomeworkproblemsinCryptographyandNetworkSecurity,FourthEditionIfyouspotanerrorinasolutionorinthewordingofaproblem,IwouldgreatlyappreciateitifyouwouldforwardtheinformationviaemailtowsshorenetAnerratasheetforthismanual,ifneeded,isavailableatftp:shellshorenetmemberswswsSWSTABLEOFCONTENTSChapter:IntroductionChapter:ClassicalEncryptionTechniquesChapter:BlockCiphersandtheDateEncryptionStandardChapter:FiniteFieldsChapter:AdvancedEncryptionStandardChapter:MoreonSymmetricCiphersChapter:ConfidentialityUsingSymmetricEncryptionChapter:IntroductiontoNumberTheoryChapter:PublicKeyCryptographyandRSAChapter:KeyManagementOtherPublicKeyCryptosystemsChapter:MessageAuthenticationandHashFunctionsChapter:HashandMACAlgorithmsChapter:DigitalSignaturesandAuthenticationProtocolsChapter:AuthenticationApplicationsChapter:ElectronicMailSecurityChapter:IPSecurityChapter:WebSecurityChapter:IntrudersChapter:MaliciousSoftwareChapter:FirewallsANSWERSTOQUESTIONSTheOSISecurityArchitectureisaframeworkthatprovidesasystematicwayofdefiningtherequirementsforsecurityandcharacterizingtheapproachestosatisfyingthoserequirementsThedocumentdefinessecurityattacks,mechanisms,andservices,andtherelationshipsamongthesecategoriesPassiveattackshavetodowitheavesdroppingon,ormonitoring,transmissionsElectronicmail,filetransfers,andclientserverexchangesareexamplesoftransmissionsthatcanbemonitoredActiveattacksincludethemodificationoftransmitteddataandattemptstogainunauthorizedaccesstocomputersystemsPassiveattacks:releaseofmessagecontentsandtrafficanalysisActiveattacks:masquerade,replay,modificationofmessages,anddenialofserviceAuthentication:TheassurancethatthecommunicatingentityistheonethatitclaimstobeAccesscontrol:Thepreventionofunauthorizeduseofaresource(ie,thisservicecontrolswhocanhaveaccesstoaresource,underwhatconditionsaccesscanoccur,andwhatthoseaccessingtheresourceareallowedtodo)Dataconfidentiality:TheprotectionofdatafromunauthorizeddisclosureDataintegrity:Theassurancethatdatareceivedareexactlyassentbyanauthorizedentity(ie,containnomodification,insertion,deletion,orreplay)Nonrepudiation:ProvidesprotectionagainstdenialbyoneoftheentitiesinvolvedinacommunicationofhavingparticipatedinallorpartofthecommunicationAvailabilityservice:Thepropertyofasystemorasystemresourcebeingaccessibleandusableupondemandbyanauthorizedsystementity,accordingtoperformancespecificationsforthesystem(ie,asystemisavailableifitprovidesservicesaccordingtothesystemdesignwheneverusersrequestthem)SeeTableCHAPTERINTRODUCTIONANSWERSTOPROBLEMSReleaseofmessagecontentsTrafficanalysisMasqueradeReplayModificationofmessagesDenialofservicePeerentityauthenticationYDataoriginauthenticationYAccesscontrolYConfidentialityYTrafficflowconfidentialityYDataintegrityYYNonrepudiationYAvailabilityYReleaseofmessagecontentsTrafficanalysisMasqueradeReplayModificationofmessagesDenialofserviceEnciphermentYDigitalsignatureYYYAccesscontrolYYYYYDataintegrityYYAuthenticationexchangeYYYYTrafficpaddingYRoutingcontrolYYYNotarizationYYYANSWERSTOQUESTIONSPlaintext,encryptionalgorithm,secretkey,ciphertext,decryptionalgorithmPermutationandsubstitutionOnekeyforsymmetricciphers,twokeysforasymmetricciphersAstreamcipherisonethatencryptsadigitaldatastreamonebitoronebyteatatimeAblockcipherisoneinwhichablockofplaintextistreatedasawholeandusedtoproduceaciphertextblockofequallengthCryptanalysisandbruteforceCiphertextonlyOnepossibleattackunderthesecircumstancesisthebruteforceapproachoftryingallpossiblekeysIfthekeyspaceisverylarge,thisbecomesimpracticalThus,theopponentmustrelyonananalysisoftheciphertextitself,generallyapplyingvariousstatisticalteststoitKnownplaintextTheanalystmaybeabletocaptureoneormoreplaintextmessagesaswellastheirencryptionsWiththisknowledge,theanalystmaybeabletodeducethekeyonthebasisofthewayinwhichtheknownplaintextistransformedChosenplaintextIftheanalystisabletochoosethemessagestoencrypt,theanalystmaydeliberatelypickpatternsthatcanbeexpectedtorevealthestructureofthekeyAnencryptionschemeisunconditionallysecureiftheciphertextgeneratedbytheschemedoesnotcontainenoughinformationtodetermineuniquelythecorrespondingplaintext,nomatterhowmuchciphertextisavailableAnencryptionschemeissaidtobecomputationallysecureif:()thecostofbreakingthecipherexceedsthevalueoftheencryptedinformation,and()thetimerequiredtobreakthecipherexceedstheusefullifetimeoftheinformationTheCaesarcipherinvolvesreplacingeachletterofthealphabetwiththeletterstandingkplacesfurtherdownthealphabet,forkintherangethroughAmonoalphabeticsubstitutionciphermapsaplaintextalphabettoaciphertextalphabet,sothateachletteroftheplaintextalphabetmapstoasingleuniqueletteroftheciphertextalphabetThePlayfairalgorithmisbasedontheuseofa´matrixoflettersconstructedusingakeywordPlaintextisencryptedtwolettersatatimeusingthismatrixCHAPTERCLASSICALENCRYPTIONTECHNIQUESRApolyalphabeticsubstitutioncipherusesaseparatemonoalphabeticsubstitutioncipherforeachsuccessiveletterofplaintext,dependingonakeyThereisthepracticalproblemofmakinglargequantitiesofrandomkeysAnyheavilyusedsystemmightrequiremillionsofrandomcharactersonaregularbasisSupplyingtrulyrandomcharactersinthisvolumeisasignificanttaskEvenmoredauntingistheproblemofkeydistributionandprotectionForeverymessagetobesent,akeyofequallengthisneededbybothsenderandreceiverThus,amammothkeydistributionproblemexistsAtranspositioncipherinvolvesapermutationoftheplaintextlettersSteganographyinvolvesconcealingtheexistenceofamessageANSWERSTOPROBLEMSaNoAchangeinthevalueofbshiftstherelationshipbetweenplaintextlettersandciphertextletterstotheleftorrightuniformly,sothatifthemappingisonetooneitremainsonetooneb,,,,,,,,,,,,AnyvalueofalargerthanisequivalenttoamodcThevaluesofaandmusthavenocommonpositiveintegerfactorotherthanThisisequivalenttosayingthataandarerelativelyprime,orthatthegreatestcommondivisorofaandisToseethis,firstnotethatE(a,p)=E(a,q)(≤p≤q<)ifandonlyifa(p–q)isdivisiblebySupposethataandarerelativelyprimeThen,a(p–q)isnotdivisibleby,becausethereisnowaytoreducethefractionaand(p–q)islessthanSupposethataandhaveacommonfactork>ThenE(a,p)=E(a,q),ifq=pmk≠pThereareallowablevaluesofa(,,,,,,,,,,,)Thereareallowablevaluesofb,fromthrough)ThusthetotalnumberofdistinctaffineCaesarciphersis´=AssumethatthemostfrequentplaintextletteriseandthesecondmostfrequentletteristNotethatthenumericalvaluesaree=B=t=U=Thenwehavethefollowingequations:=(ab)mod=(ab)modThus,=amodBytrialanderror,wesolve:a=Then=(b)modByobservation,b=AgoodglassintheBishop'shostelintheDevil'sseattwentyonedegreesandthirteenminutesnortheastandbynorthmainbranchseventhlimbeastsideshootfromthelefteyeofthedeath'sheadabeelinefromthetreethroughtheshotfiftyfeetout(fromTheGoldBug,byEdgarAllanPoe)aThefirstlettertcorrespondstoA,thesecondletterhcorrespondstoB,eisC,sisD,andsoonSecondandsubsequentoccurrencesofaletterinthekeysentenceareignoredTheresultciphertext:SIDKHKDMAFHCRKIABIESHIMCKDLFEAILAplaintext:basilisktoleviathanblakeiscontactbItisamonalphabeticcipherandsoeasilybreakablecThelastsentencemaynotcontainallthelettersofthealphabetIfthefirstsentenceisused,thesecondandsubsequentsentencesmayalsobeuseduntilalllettersareencounteredThecipherreferstothewordsinthepageofabookThefirstentry,,referstopageThesecondentry,C,referstocolumntwoTheremainingnumbersarewordsinthatcolumnThenamesDOUGLASandBIRLSTONEaresimplywordsthatdonotappearonthatpageElementary!(fromTheValleyofFear,bySirArthurConanDoyle)aCRYPTOGAHIBEATTHETHIRDPILLARFROMTHELEFTOUTSIDETHELYCEUMTHEATRETONIGHTATSEVENIFYOUAREDISTRUSTFULBRINGTWOFRIENDSNETWORKSCUTRFHEHFTINBROUYRTUSTEAETHGISREHFTEATYRNDIROLTAOUGSHLLETINIBITIHIUOVEUFEDMTCESATWTLEDMNEDLRAPTSETERFOISRNGBUTLFRRAFRLIDLPFTIYONVSEETBEHIHTETAEYHATTUCMEHRGTAIOENTTUSRUIEADRFOETOLHMETNTEDSIFWROHUTELEITDSbThetwomatricesareusedinreverseorderFirst,theciphertextislaidoutincolumnsinthesecondmatrix,takingintoaccounttheorderdictatedbythesecondmemorywordThen,thecontentsofthesecondmatrixarereadlefttoright,toptobottomandlaidoutincolumnsinthefirstmatrix,takingintoaccounttheorderdictatedbythefirstmemorywordTheplaintextisthenreadlefttoright,toptobottomcAlthoughthisisaweakmethod,itmayhaveusewithtimesensitiveinformationandanadversarywithoutimmediateaccesstogoodcryptanalysis(eg,tacticaluse)Plusitdoesn'trequireanythingmorethanpaperandpencil,andcanbeeasilyrememberedSPUTNIKPTBOATONEOWENINELOSTINACTIONINBLACKETTSTRAITTWOMILESSWMERESUCOVEXCREWOFTWELVEXREQUESTANYINFORMATIONaLARGESTBCDFHIJKMNOPQUVWXYZbOCURENABDFGHIJKLMPQSTVWXYZaUZTBDLGZPNNWLGTGTUEROVLDBDUHFPERHWQSRZbUZTBDLGZPNNWLGTGTUEROVLDBDUHFPERHWQSRZcAcyclicrotationofrowsandorcolumnsleadstoequivalentsubstitutionsInthiscase,thematrixforpartaofthisproblemisobtainedfromthematrixofProblema,byrotatingthecolumnsbyonestepandtherowsbythreestepsa!»bGivenanyxconfiguration,anyofthefourrowrotationsisequivalent,foratotaloffiveequivalentconfigurationsForeachofthesefiveconfigurations,anyofthefourcolumnrotationsisequivalentSoeachconfigurationinfactrepresentsequivalentconfigurationsThus,thetotalnumberofuniquekeysis!=!AmixedCaesarcipherTheamountofshiftisdeterminedbythekeyword,whichdeterminestheplacementoflettersinthematrixaDifficultiesarethingsthatshowwhatmenarebIrrationallyheldtruthsmaybemoreharmfulthanreasonederrorsaWeneedanevennumberofletters,soappenda"q"totheendofthemessageThenconvertthelettersintothecorrespondingalphabeticpositions:MeetmeattheusualPlaceattenratherThaneightoclockqThecalculationsproceedtwolettersatatimeThefirstpair:CCæèçöø÷=æèçöø÷æèçöø÷mod=æèçöø÷mod=æèçöø÷Thefirsttwociphertextcharactersarealphabeticpositionsand,whichcorrespondtoGVThecompleteciphertext:GVUIGVKODZYPUHEKJHUZWFZFWSJSDZMUDZMYCJQMFWWUQRKRbWefirstperformamatrixinversionNotethatthedeterminateoftheencryptionmatrixis(´)–(´)=Usingthematrixinversionformulafromthebook:æèçöø÷=æèçöø÷mod=æèçöø÷mod=æèçöø÷mod=æèçöø÷Hereweusedthefactthat()–=inZOncetheinversematrixhasbeendetermined,decryptioncanproceedSource:LEWAConsiderthematrixKwithelementskijtoconsistofthesetofcolumnvectorsKj,where:K=kLknMMMknLknnæèçççöø÷÷÷andKj=kjMknjæèçççöø÷÷÷TheciphertextofthefollowingchosenplaintextngramsrevealsthecolumnsofK:(B,A,A,…,A,A)«K(A,B,A,…,A,A)«K:(A,A,A,…,A,B)«Kna´b´cd´e´f´(–)´ghikey:legleglegleplaintext:explanationciphertext:PBVWETLXOZRasendmoremoneyBECKJDMSXZPMHbcashnotneededBECKJDMSXZPMHyourpackagereadyFridaystroomthreePleasedestroythisimmediatelyaLaythemessageoutinamatrixlettersacrossEachintegerinthekeytellsyouwhichlettertochooseinthecorrespondingrowResult:HesittethbetweenthecherubimsTheislesmaybegladthereofAstheriversinthesouthbQuitesecureIneachrowthereisoneofeightpossibilitiesSoiftheciphertextisnlettersinlength,thenthenumberofpossibleplaintextsisncNotverysecureLordPeterfigureditout(fromTheNineTailors)ANSWERSTOQUESTIONSMostsymmetricblockencryptionalgorithmsincurrentusearebasedontheFeistelblockcipherstructureTherefore,astudyoftheFeistelstructurerevealstheprinciplesbehindthesemorerecentciphersAstreamcipherisonethatencryptsadigitaldatastreamonebitoronebyteatatimeAblockcipherisoneinwhichablockofplaintextistreatedasawholeandusedtoproduceaciphertextblockofequallengthIfasmallblocksize,suchasn=,isused,thenthesystemisequivalenttoaclassicalsubstitutioncipherForsmalln,suchsystemsarevulnerabletoastatisticalanalysisoftheplaintextForalargeblocksize,thesizeofthekey,whichisontheorderofn´n,makesthesystemimpracticalInaproductcipher,twoormorebasicciphersareperformedinsequenceinsuchawaythatthefinalresultorproductiscryptographicallystrongerthananyofthecomponentciphersIndiffusion,thestatisticalstructureoftheplaintextisdissipatedintolongrangestatisticsoftheciphertextThisisachievedbyhavingeachplaintextdigitaffectthevalueofmanyciphertextdigits,whichisequivalenttosayingthateachciphertextdigitisaffectedbymanyplaintextdigitsConfusionseekstomaketherelationshipbetweenthestatisticsoftheciphertextandthevalueoftheencryptionkeyascomplexaspossible,againtothwartattemptstodiscoverthekeyThus,eveniftheattackercangetsomehandleonthestatisticsoftheciphertext,thewayinwhichthekeywasusedtoproducethatciphertextissocomplexastomakeitdifficulttodeducethekeyThisisachievedbytheuseofacomplexsubstitutionalgorithmBlocksize:Largerblocksizesmeangreatersecurity(allotherthingsbeingequal)butreducedencryptiondecryptionspeedKeysize:LargerkeysizemeansgreatersecuritybutmaydecreaseencryptiondecryptionspeedNumberofrounds:TheessenceoftheFeistelcipheristhatasingleroundoffersinadequatesecuritybutthatmultipleroundsofferincreasingsecuritySubkeygenerationalgorithm:GreatercomplexityinthisalgorithmshouldleadtogreaterdifficultyofcryptanalysisRoundfunction:Again,greatercomplexitygenerallymeansgreaterresistancetocryptanalysisFastsoftwareencryptiondecryption:Inmanycases,encryptionisembeddedinapplicationsorutilityfunctionsinsuchawayastoCHAPTERBLOCKCIPHERSANDTHEDATAENCRYPTIONSTANDARDprecludeahardwareimplementationAccordingly,thespeedofexecutionofthealgorithmbecomesaconcernEaseofanalysis:Alt

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  • 909714152 我还想要这本书的电子档呢 不知道谁有 共享一下

    2011-11-07 23:57:03

  • 123.116.37.51 多谢了,英文第四版答案,正是我要的.

    2011-08-30 07:16:40

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密码编码学与网络安全:原理与实践+第四版习题解答

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