密码编码学与网络安全(第五版)答案.docx

密码编码学与网络安全(第五版)答案.docx

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Chapter1:

Introduction 5

Chapter2:

ClassicalEncryptionTechniques 7

Chapter3:

BlockCiphersandtheDateEncryptionStandard 13

Chapter4:

FiniteFields 21

Chapter5:

AdvancedEncryptionStandard 28

Chapter6:

MoreonSymmetricCiphers 33

Chapter7:

ConfidentialityUsingSymmetricEncryption 38

Chapter8:

IntroductiontoNumberTheory 42

Chapter9:

Public-KeyCryptographyandRSA 46

Chapter10:

KeyManagement;OtherPublic-KeyCryptosystems 55

Chapter11:

MessageAuthenticationandHashFunctions 59

Chapter12:

HashandMACAlgorithms 62

Chapter13:

DigitalSignaturesandAuthenticationProtocols 66

Chapter14:

AuthenticationApplications 71

Chapter15:

ElectronicMailSecurity 73

Chapter16:

IPSecurity 76

Chapter17:

WebSecurity 80

Chapter18:

Intruders 83

Chapter19:

MaliciousSoftware 87

Chapter20:

Firewalls 89

AnswerstoQuestions

1.1 TheOSISecurityArchitectureisaframeworkthatprovidesasystematicwayofdefiningtherequirementsforsecurityandcharacterizingtheapproachestosatisfyingthoserequirements.Thedocumentdefinessecurityattacks,mechanisms,andservices,andtherelationshipsamongthesecategories.

1.2 Passiveattackshavetodowitheavesdroppingon,ormonitoring,transmissions.Electronicmail,filetransfers,andclient/serverexchangesareexamplesoftransmissionsthatcanbemonitored.Activeattacksincludethemodificationoftransmitteddataandattemptstogainunauthorizedaccesstocomputersystems.

1.3 Passiveattacks:

releaseofmessagecontentsandtrafficanalysis.Activeattacks:

masquerade,replay,modificationofmessages,anddenialofservice.

1.4 Authentication:

Theassurancethatthecommunicatingentityistheonethatitclaimstobe.

Accesscontrol:

Thepreventionofunauthorizeduseofaresource（i.e.,thisservicecontrolswhocanhaveaccesstoaresource,underwhatconditionsaccesscanoccur,andwhatthoseaccessingtheresourceareallowedtodo）.

Dataconfidentiality:

Theprotectionofdatafromunauthorizeddisclosure.

Dataintegrity:

Theassurancethatdatareceivedareexactlyassentbyanauthorizedentity（i.e.,containnomodification,insertion,deletion,orreplay）.

Nonrepudiation:

Providesprotectionagainstdenialbyoneoftheentitiesinvolvedinacommunicationofhavingparticipatedinallorpartofthecommunication.

Availabilityservice:

Thepropertyofasystemorasystemresourcebeingaccessibleandusableupondemandbyanauthorizedsystementity,accordingtoperformancespecificationsforthesystem（i.e.,asystemisavailableifitprovidesservicesaccordingtothesystemdesignwheneverusersrequestthem）.

1.5 SeeTable1.3.

AnswerstoProblems

1.1

Releaseofmessagecontents

Trafficanalysis

Masquerade

Replay

Modificationofmessages

Denialofservice

Peerentityauthentication

Y

Dataoriginauthentication

Y

Accesscontrol

Y

Confidentiality

Y

Trafficflowconfidentiality

Y

Dataintegrity

Y

Y

Non-repudiation

Y

Availability

Y

1.2

Releaseofmessagecontents

Trafficanalysis

Masquerade

Replay

Modificationofmessages

Denialofservice

Encipherment

Y

Digitalsignature

Y

Y

Y

Accesscontrol

Y

Y

Y

Y

Y

Dataintegrity

Y

Y

Authenticationexchange

Y

Y

Y

Y

Trafficpadding

Y

Routingcontrol

Y

Y

Y

Notarization

Y

Y

Y

Chapter2

ClassicalEncryptionTechniquesr

AnswerstoQuestions

2.1 Plaintext,encryptionalgorithm,secretkey,ciphertext,decryptionalgorithm.

2.2 Permutationandsubstitution.

2.3 Onekeyforsymmetricciphers,twokeysforasymmetricciphers.

2.4 Astreamcipherisonethatencryptsadigitaldatastreamonebitoronebyteatatime.Ablockcipherisoneinwhichablockofplaintextistreatedasawholeandusedtoproduceaciphertextblockofequallength.

2.5 Cryptanalysisandbruteforce.

2.6 Ciphertextonly.Onepossibleattackunderthesecircumstancesisthebrute-forceapproachoftryingallpossiblekeys.Ifthekeyspaceisverylarge,thisbecomesimpractical.Thus,theopponentmustrelyonananalysisoftheciphertextitself,generallyapplyingvariousstatisticalteststoit.Knownplaintext.Theanalystmaybeabletocaptureoneormoreplaintextmessagesaswellastheirencryptions.Withthisknowledge,theanalystmaybeabletodeducethekeyonthebasisofthewayinwhichtheknownplaintextistransformed.Chosenplaintext.Iftheanalystisabletochoosethemessagestoencrypt,theanalystmaydeliberatelypickpatternsthatcanbeexpectedtorevealthestructureofthekey.

2.7 Anencryptionschemeisunconditionallysecureiftheciphertextgeneratedbytheschemedoesnotcontainenoughinformationtodetermineuniquelythecorrespondingplaintext,nomatterhowmuchciphertexti