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Lecture12:Mid-termReviewSchoolofSoftwareEngineering,CQUFall,2021AnIntroductionto
InformationSecurity2
2025/4/2AnIntroductiontoInformationSecurityLecture1:PrefaceTheCategoriesofattacks:Generally,therearefourgeneralcategoriesofsecurityattacksInterruption阻斷Interception竊聽Modification修改Fabrication偽裝1.AboutIS2.WWWIS?3.S_Attacks4.S_ServicesInformationsourceInformationdestinationAnassetofthesystemisdestroyedorbecomesunavailableorunusable.Thisisanattackonavailability.Examplesinclude:destructionofapieceofhardwarethecuttingofacommunicationlinethedisablingofthefilemanagementsystemDOS/DDOS(DenialofService)3
2025/4/2AnIntroductiontoInformationSecurityLecture1:Preface1.AboutIS2.WWWIS?3.S_Attacks4.S_ServicesTheCategoriesofattacks:Generally,therearefourgeneralcategoriesofsecurityattacksInterruption阻斷Interception竊聽Modification修改Fabrication偽裝InformationsourceInformationdestinationThirdpartyAnunauthorizedpartygainsaccesstoanasset.Thisisanattackonconfidentiality(保密性).
egs:wiretapping(竊聽)
tocapturedatainanetworktheillicit(非法)copyingoffilesorprograms……4
2025/4/2AnIntroductiontoInformationSecurityLecture1:PrefaceTheCategoriesofattacks:Generally,therearefourgeneralcategoriesofsecurityattacksInterruption阻斷Interception竊聽Modification修改Fabrication偽裝1.AboutIS2.WWWIS?3.S_Attacks4.S_ServicesInformationsourceInformationdestinationThirdpartyAnunauthorizedpartynotonlygainsaccesstobuttampers(篡改)
withanasset.Thisisanattackondeniability/integrity(完整性).Examplesare:changingvaluesinadatafilealteringaprogrammodifyingthecontentofmessages
……5
2025/4/2AnIntroductiontoInformationSecurityLecture1:PrefaceTheCategoriesofattacks:Generally,therearefourgeneralcategoriesofsecurityattacksInterruption阻斷Interception竊聽Modification修改Fabrication偽裝1.AboutIS2.WWWIS?3.S_Attacks4.S_ServicesInformationsourceInformationdestinationThirdpartyAnunauthorizedpartyinsertscounterfeit(假冒的)objectsintothesystem.Thisisanattackonauthenticity(真實性).Examplesare:insertionofspuriousmessagesinanetworkadditionofrecordstoafile……6
2025/4/2AnIntroductiontoInformationSecurityLecture1:Preface1.AboutIS2.WWWIS?3.S_Attacks4.S_ServicesTheseattacksinvolvessomemodificationofthedatastreamorthecreationofafalsestream,whichcanbesubdividedintofourcategories:masquerade(偽裝)replay(重放)modificationofmessages(篡改)denialofservice(拒絕效勞)Activeattackspresenttheoppositecharacteristicsofpassiveattacks:Easytodetectbuthardtoprevent！ActiveAttackPassiveattackand7
2025/4/2AnIntroductiontoInformationSecurityLecture1:Preface1.AboutIS2.WWWIS?3.S_Attacks4.S_ServicesPassiveattacksareinthenatureofeavesdropping(偷聽)on,ormonitoringof,transmissions.Thegoaloftheopponentistoobtaininformationthatisbeingtransmitted.Twotypesofpassiveattacksare:
releaseofmessagecontents(泄密)
trafficanalysis(流量分析)passiveattackspresenttheoppositecharacteristicsofactiveattacks:Easytopreventbuthardtodetect！ActiveAttackPassiveattackand8
2025/4/2AnIntroductiontoInformationSecurityLecture1:PrefaceSecurityServicesConfidentiality(保密性)Availability(可用性)Nonrepudiation(防抵賴)Authentication(真實性)Integrity(完整性)AccessControl(可控性)1.AboutIS2.WWWIS?3.S_Attacks4.S_ServicesEnsuresthattheinformationinanetworkandtransmittedinformationareaccessibleonlyforreadingbyauthorizedparties.AssetsAuthorizedPartyUnauthorized
Party9
2025/4/2AnIntroductiontoInformationSecurityLecture1:PrefaceSecurityServicesConfidentiality(保密性)Availability(可用性)Nonrepudiation(防抵賴)Authentication(真實性)Integrity(完整性)AccessControl(可控性)1.AboutIS2.WWWIS?3.S_Attacks4.S_ServicesRequiresthatcomputerassetsbeavailabletoauthorizedpartiesasneeded.AssetsAuthorizedParty10
2025/4/2AnIntroductiontoInformationSecurityLecture1:PrefaceSecurityServicesConfidentiality(保密性)Availability(可用性)Nonrepudiation(防抵賴)Authentication(真實性)Integrity(完整性)AccessControl(可控性)1.AboutIS2.WWWIS?3.S_Attacks4.S_ServicesRequiresthatneitherthesendernorthereceiverofamessagebeabletodenythetransmission.ReceiverSenderIdidn’tsendRthemessage!Ididn'treceivethemessagefromS!11
2025/4/2AnIntroductiontoInformationSecurityLecture1:PrefaceSecurityServicesConfidentiality(保密性)Availability(可用性)Nonrepudiation(防抵賴)Authentication(真實性)Integrity(完整性)AccessControl(可控性)1.AboutIS2.WWWIS?3.S_Attacks4.S_ServicesEnsuresthattheoriginofamessageorelectronicdocumentiscorrectlyidentified,withanassurancethattheidentityisnotfalse.AuthorityIdentityIchbinXiaofeng+CredentialVerifyUserandCredentialAuthorizedAssets12
2025/4/2AnIntroductiontoInformationSecurityLecture1:PrefaceSecurityServicesConfidentiality(保密性)Availability(可用性)Nonrepudiation(防抵賴)Authentication(真實性)Integrity(完整性)AccessControl(可控性)1.AboutIS2.WWWIS?3.S_Attacks4.S_ServicesEnsurethesystemwiththecapabilitytodenyanymodificationsandtransmissionsofassetsfromun-authorizedparties.Inotherwords,onlyauthorizepartiesareabletomodifyassetsandtransmittedinformation.sourcedestinationUn-authorizedparty13
2025/4/2AnIntroductiontoInformationSecurityLecture1:PrefaceSecurityServicesConfidentiality(保密性)Availability(可用性)Nonrepudiation(防抵賴)Authentication(真實性)Integrity(完整性)AccessControl(可控性)1.AboutIS2.WWWIS?3.S_Attacks4.S_ServicesRequiresthataccesstoinformationresourcesmaybecontrolled
byorforthetargetsystem.eg:UserAssetsReadWriteAccess14
2025/4/2AnIntroductiontoInformationSecurityLecture2:OverviewofCryptography1.
WWWCryptography2.ClassicCryptographyTerminology:homoionym(近義詞)Cryptography密碼編碼學encrypt,decryptencryption,decryptioncode,codingencode,decodecipher,cipheringencipher,deciphermessagecodemessageencryptdecryptplaintextciphertext15
2025/4/2AnIntroductiontoInformationSecurityLecture2:OverviewofCryptography1.
WWWCryptography2.ClassicCryptographyTerminology:homoionym(近義詞)Cryptography密碼編碼學encrypt,decryptencryption,decryptioncode,codingencode,decodecipher,cipheringencipher,deciphermessagecodemessageencryptdecryptplaintextciphertext16
2025/4/2AnIntroductiontoInformationSecurityLecture2:OverviewofCryptography1.
WWWCryptography2.ClassicCryptographyCryptographyClassicCryptography:〔byWWII〕typicallyforconfidentialusageAandBhavealreadysharedsecretinformation,toprotecttheircommunicationModernCryptography〔fromWWII〕relatedtomoresecurityservices,as:confidentiality,integrity,authentication,andnon-repudiation.SymmetricCryptographyAsymmetricCryptographyCryptographicHashFunctionModernCryptography17
2025/4/2AnIntroductiontoInformationSecurityLecture2:OverviewofCryptography1.
WWWCryptography2.ClassicCryptographySymmetricC-AsymmetricC-C-HashFunctionSymmetric-keycipher：encryptionanddecryptionwith
thesamesecretkeyGeneralideaofSymmetric-keycipherPlaintextPlaintextCiphertextCiphertextDecryption
AlgorithmEncryption
AlgorithmSecureKey-exchangeChannelInsecureChannelShared
Secret-KeyShared
Secret-KeyAliceBob18
2025/4/2AnIntroductiontoInformationSecurityLecture2:OverviewofCryptography1.
WWWCryptography2.ClassicCryptographySymmetricC-AsymmetricC-C-HashFunctionAsymmetric-keycipher:encryptionanddecryptionwithdifferentkeysPlaintextPlaintextCiphertextCiphertextDecryption
AlgorithmEncryption
AlgorithmInsecureChannelAliceBobGeneralideaofAsymmetric-keycipher(1)Alice’s
Private-KeyAlice’sPublicKey19
2025/4/2AnIntroductiontoInformationSecurityLecture2:OverviewofCryptography1.
WWWCryptography2.ClassicCryptographySymmetricC-AsymmetricC-C-HashFunctionAsymmetric-keycipher:encryptionanddecryptionwithdifferentkeysPlaintextPlaintextCiphertextCiphertextEncryption
AlgorithmDecryption
AlgorithmInsecureChannelAliceBobGeneralideaofAsymmetric-keycipher(2)Alice’s
Private-KeyAlice’sPublicKey20
2025/4/2AnIntroductiontoInformationSecurityLecture2:OverviewofCryptography1.
WWWCryptography2.ClassicCryptographySymmetricC-AsymmetricC-C-HashFunctionCryptographicHashFunction:密碼散列函數withorwithoutsecretkeyGeneralideaofHashFunctionforMessageDigestHashFunctionHashFunctionInsecureChannelAliceBob×MdigestmessageMdigestMdigest’21
2025/4/2AnIntroductiontoInformationSecurityLecture3:OverviewofCryptography(II)1.1Kerckhoff’sPrinciplea.k.a.,Kerckhoffs'assumption,axiomorlawacryptosystemshouldbesecureevenifeverythingaboutthesystem,exceptthekey,ispublicknowledge.密碼系統的平安性不在于算法的保密，而在于當對手獲知了算法和密文后分析出密鑰或明文的難度。1.MoreConceptsofCryptography3…
2…
AugusteKerckhoffs
1835-1903
What?“Theenemyknowsthesystem.〞——byClaudeShannonShannon'smaxim22
2025/4/2AnIntroductiontoInformationSecurityLecture3:OverviewofCryptography(II)1.2ConfusionandDiffusionConfusion:(混淆)makingtherelationshipbetweenthekeyandtheciphertextascomplexandinvolvedaspossible;Diffusion:(擴散)thepropertythattheredundancyinthestatisticsoftheplaintextis"dissipated"inthestatisticsoftheciphertext;1.MoreConceptsofCryptography3…
2…
ClaudeElwoodShannon(April30,1916–February24,2001),anAmericanelectronicengineerandmathematician,isknownas"thefatherofinformationtheory".23
2025/4/2AnIntroductiontoInformationSecurityLecture3:OverviewofCryptography(II)1.3AvalancheeffectIncryptography,theavalancheeffectreferstoadesirablepropertyofcryptographicalgorithms,typicallyblockciphersandcryptographichashfunctions.Theavalancheeffectisevidentif,whenaninputischangedslightly(forexample,flippingasinglebit)theoutputchangessignificantly(e.g.,halftheoutputbitsflip)Inthecaseofqualityblockciphers,suchasmallchangeineitherthekeyortheplaintextshouldcauseadrasticchangeintheciphertext;1.MoreConceptsofCryptography3…
2…
24
2025/4/2AnIntroductiontoInformationSecurityLecture3:OverviewofCryptography(II)1.4SubstitutionCipherAsubstitutioncipherreplacesonesymbolwithanother.Substitutioncipherscanbecategorizedaseithermonoalphabeticciphersorpolyalphabeticciphers.TranspositionCipherAtranspositioncipherdoesnotsubstituteonesymbolforanother,insteaditchangesthelocationofthesymbols.1.MoreConceptsofCryptography3…
2…
25
2025/4/2AnIntroductiontoInformationSecurityLecture3:OverviewofCryptography(II)1.5
Blockcipher
andStreamCipher1.MoreConceptsofCryptography3…
2…
Agroupofplaintextsymbolsofsizem(m>1)areencryptedtogethercreatingagroupofciphertextofthesamesize.Asinglekeyisusedtoencryptthewholeblockevenifthekeyismadeofmultiplevalues.plaintext{T,X,T}=EK{e,x,t}{H,E,R}=EK{i,n,t}{C,I,P}=EK{p,l,a}CIPHERTXTEncryptionalgorithmK26
2025/4/2AnIntroductiontoInformationSecurityLecture3:OverviewofCryptography(II)1.5
Blockcipher
andSteramCipher1.MoreConceptsofCryptography3…
2…
Inastreamciphertheplaintextdigitsareencryptedoneatatime,andthetransformationofsuccessivedigitsvariesduringtheencryption.plaintextP=EK3(a)I=EK2(l)C=EK1(p)CHERTXTEncryptionalgorithmK=(k1,k2,k2…)………..………..IP27
2025/4/2AnIntroductiontoInformationSecurityLecture4:BlockCipherPrinciplesP-box
S-boxXORCircularShiftSwapSplit/Combine1.ProductCipher3…
2…
AP-box(permutationbox)parallelsthetraditionaltranspositioncipherforcharacters.Ittransposes(移動)bits.Astraight(直接的)P-boxisinvertible(可逆的),butcompressionandexpansionP-boxesarenot.e.g.StraightP-boxcompressionP-boxexpansionP-box28
2025/4/2AnIntroductiontoInformationSecurityLecture4:BlockCipherPrinciplesP-boxS-box
XORCircularShiftSwapSplit/Combine1.ProductCipher3…
2…
AnS-box(substitution
box)canbethoughtofasaminiature(微小的)substitutioncipher.AnS-boxisanm×nsubstitutionunit,wheremandnarenotnecessarilythesame.110110100129
2025/4/2AnIntroductiontoInformationSecurityLecture4:BlockCipherPrinciples
P-boxS-boxXORCircularShiftSwapSplit/Combine1.ProductCipher3…
2…
Theexclusive-oroperationisanimportantcomponentinmostblockciphers.XOR01001110+e.g.AxorBxorB=?30
2025/4/2AnIntroductiontoInformationSecurityLecture4:BlockCipherPrinciples
P-boxS-boxXORCircularShiftSwapSplit/Combine1.ProductCipher3…
2…
Thecircularshiftoperationisanothercomponentfoundinsomemodernblockciphers.e.g.31
2025/4/2AnIntroductiontoInformationSecurityLecture4:BlockCipherPrinciples
P-boxS-boxXORCircularShiftSwapSplit/Combine1.ProductCipher3…
2…
Theswapoperationisaspecialcaseofthecircularshiftoperationwherek=n/2.e.g.32
2025/4/2AnIntroductiontoInformationSecurityLecture4:BlockCipherPrinciples
P-boxS-boxXORCircularShiftSwapSplit/Combine1.ProductCipher3…
2…
Twootheroperationsfoundinsomeblockciphersaresplitandcombine.e.g.SplitCombine33
2025/4/2AnIntroductiontoInformationSecurityLecture4:BlockCipherPrinciplesProductCipher:asimpleexample1.ProductCipher3…
2…
8bitplaintextblock1block2……blocknkeymixerS-box3S-box1S-box2S-box412345678P-box8bitmiddletextk18bitmiddletextk28bitciphertextRound1Round2RoundKeyGeneratorK34
2025/4/2AnIntroductiontoInformationSecurityLecture4:BlockCipherPrinciplesFeistelcipherisasymmetricstructureusedintheconstructionofblockciphersbasedonconceptofinvertibleproductcipher.implementsShannon’sS-Pnetconceptpartitionsinputblockintotwohalvesprocessthroughmultipleroundswhichbasedonroundfunctionofrighthalf&subkeythenhavepermutationswappinghalves2.TheFeistelCipher3…
1…
HorstFeistel
1915-1990LiRi+Li+1Ri+1FKiLi+1Ri+135
2025/4/2AnIntroductiontoInformationSecurityLecture4:BlockCipherPrinciplesFeistelCipher:PropertiesBlocksizeKeysizeNumberofroundsSubkeygenerationRoundfunctionFastsoftwareE/DEaseofanalysis2.TheFeistelCipher3…
1…
36
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.1DESEncryption:WholePictureTheencryptionprocessismadeof2permutations(P-boxes),whichwecallinitial(初始)andfinalpermutations,and16Feistelrounds.1.DataEncryptionStandard3…
2…
DES64bitplaintext64bitciphertextInitialpermutationRound1Round2Round16Finalpermutation.
...
..56bitkeyK1K2K16Round-keygenerator37
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.1DESEncryption:InitialandFinalPermutationsInitialPermutations:IPFinalPermutations:IP-1TheinitialandfinalpermutationsarestraightP-boxesthatareinverses(互逆的)ofeachother.Theyhavenomuchcryptographicsignificance(意義)inDES.1.DataEncryptionStandard3…
2…
38
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.1DESEncryption:RoundsDESuses16rounds.EachroundofDESisaFeistelcipher.1.DataEncryptionStandard3…
2…
AroundinDES(encryptionsite)Li=Ri-1Ri=Li-1f(Ri-1,Ki)+39
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.1DESEncryption:FeistelFunction(DESFunction)TheheartofDESistheDESfunction.TheDESfunctionappliesa48-bitround-
keytotherightmost32bitstoproduce
a32-bitoutput.1.DataEncryptionStandard3…
2…
DESfunction40
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.1DESEncryption:FeistelFunction(DESFunction)1.DataEncryptionStandard3…
2…
E-PboxSinceRi?1isa32-bitinputandKiisa48-bitkey,wefirstneedtoexpandRi?1to48bits.41
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.1DESEncryption:FeistelFunction(DESFunction)1.DataEncryptionStandard3…
2…
XOR：“Add〞RoundKeyAftertheexpansionpermutation,DESusestheXORoperationontheexpandedrightsectionandtheroundkey.Notethatboththerightsectionandthekeyare48-bitsinlength.Alsonotethat
theroundkeyisusedonlyinthisoperation.42
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.1DESEncryption:FeistelFunction(DESFunction)1.DataEncryptionStandard3…
2…
S-boxTheS-boxesdotherealmixing(confusion).
DESuses8S-boxes,eachwitha6-bitinputanda4-bitoutput.43
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.1DESEncryption:FeistelFunction(DESFunction)1.DataEncryptionStandard3…
2…
S-boxTheS-boxesdotherealmixing(confusion).
DESuses8S-boxes,eachwitha6-bitinputanda4-bitoutput.44
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.1DESEncryption:FeistelFunction(DESFunction)1.DataEncryptionStandard3…
2…
S-boxe.g.inputbits:110100Whataretheoutputbits:??TheS-boxesdotherealmixing(confusion).
DESuses8S-boxes,eachwitha6-bitinputanda4-bitoutput.45
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.1DESEncryption:FeistelFunction(DESFunction)1.DataEncryptionStandard3…
2…
S-box46
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.1DESEncryption:FeistelFunction(DESFunction)1.DataEncryptionStandard3…
2…
S-PboxThelastoperationis
StraightPermutation
withaP-boxasfollow.47
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.2DESDecryption:ThesamealgorithmasencryptionUseK1->K16asencryption,
butk16->K1asdecryption1.DataEncryptionStandard3…
2…
48
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandard2.3KeyGenerationandExpansion(擴展)64bitsRandomNumberDrop8bitsandpermutated
to
56bitsKeyTheround-keygeneratorcreates
sixteen48-bitkeysoutofa56-bit
cipherkey.Expand16sub-keyssplit56bitsto2halvesshifteachhalfcombinethemdocompresspermutationto
48bitsround-key1.DataEncryptionStandard3…
2…
49
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandardWhyMultipleEncryption?alternativestoDESexpandkeysize3.MultipleEncryptionand3-DES1…
2…
DESDESK1K2PlaintextMidtextCiphertext50
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandardDoubleDESC=EK2(EK1(P))P=DK1(DK2(C))C=DK2(EK1(P))P=DK1(EK2(C))Meet-in-the-middleattack:3.MultipleEncryptionand3-DES1…
2…
51
2025/4/2AnIntroductiontoInformationSecurityLecture5:DataEncryptionStandardTripleDESTripleDESwith2keysC=Ek1(Dk2(Ek1(P)))P=Dk1(Ek2(Dk1(C)))K1+K2:112bitsTripleDESwith3keysC=Ek3(Dk2(Ek1(P)))P=Dk1(Ek2(Dk3(C)))MoresecurethanDES,butwithmorecost3.MultipleEncryptionand3-DES1…
2…
52
2025/4/2AnIntroductiontoInformationSecurity2.1TheAESCipher:wholepicture2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕BasicDescription:1.Blocksize：128bits2.Keysize：128/192/256bits3.Rounds:10/12/144.Roundkeysize：128bits5.NotFeistelCipher
Notethat:Addroundkeybeforeround1;Nomix-columnsinlastround
53
2025/4/2AnIntroductiontoInformationSecurity2.1TheAESCipher:wholepicture2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕54
2025/4/2AnIntroductiontoInformationSecurity2.2TheAESCipher:importantconceptsfordataunitBit:1or0Byte:8bitsWord:32bitsBlock:128-bits，forinputplaintext
andoutputciphertextState:128-bits,datablockinmidstage2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕01010010010100101101011001111110110011115252D67ECFAC8723242612BAC79954D2B4177609DA55
2025/4/2AnIntroductiontoInformationSecurity2.3TheAESCipher:roundtransformations2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕1)ByteSubstitution2)ShiftRows3)MixColumns4)AddRoundkey56
2025/4/2AnIntroductiontoInformationSecurity2.3TheAESCipher:roundtransformations2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕1)ByteSubstitution2)ShiftRows3)MixColumns4)AddRoundkey57
2025/4/2AnIntroductiontoInformationSecurity2.3TheAESCipher:roundtransformations2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕1)ByteSubstitution2)ShiftRows3)MixColumns4)AddRoundkey0123456789ABCDEF0123456789ABCDEFAC2612BA87C7995423D2B417247609DA91F7C9F417C6EE2026B58DF036380157FindthelocationsinS-boxtosubstituteinputbytes915758
2025/4/2AnIntroductiontoInformationSecurity2.3TheAESCipher:roundtransformations2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕1)ByteSubstitution2)ShiftRows3)MixColumns4)AddRoundkeyAESEncryption：S-boxeg:S-box({AC})={91}AESDecryption：S-box-1eg:S-box-1({91})={AC}S-box、S-Box-1的構造過程：P11059
2025/4/2AnIntroductiontoInformationSecurity2.3TheAESCipher:roundtransformations2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕1)ByteSubstitution2)ShiftRows3)MixColumns4)AddRoundkeyThisisatransposition/permutationoperationonrows.60
2025/4/2AnIntroductiontoInformationSecurity2.3TheAESCipher:roundtransformations2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕1)ByteSubstitution2)ShiftRows3)MixColumns4)AddRoundkeyThemostcomplicatedoperationinAES61
2025/4/2AnIntroductiontoInformationSecurity2.3TheAESCipher:roundtransformations2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕1)ByteSubstitution2)ShiftRows3)MixColumns4)AddRoundkey62
2025/4/2AnIntroductiontoInformationSecurity91F7C9F4C6EE20178DF026B53638015702030101010203010101020301010203×91C68D57={02}⊙{10010001}{03}⊙{11000110}{01}⊙{10001101}{01}⊙{01010111}⊕⊕⊕=00111001010100011000110101010111⊕⊕⊕10110010B2E5xxxxxxxxxxxxxxxxxxxxxxxx32xxn×n矩陣的乘法，繼續…Example3MixColumnsLecture6:AdvancedEncryptionStandard〔AES〕63
2025/4/2AnIntroductiontoInformationSecurity2.3TheAESCipher:roundtransformations2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕1)ByteSubstitution2)ShiftRows3)MixColumns4)AddRoundkeyAESencryption：CAESdecryption：C-164
2025/4/2AnIntroductiontoInformationSecurity2.3TheAESCipher:roundtransformations2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕1)ByteSubstitution2)ShiftRows3)MixColumns4)AddRoundkeyAddRoundKeyproceedsonecolumnatatime.AddRoundKeyaddsaroundkeywordwitheachstatecolumnmatrix;theoperationinAddRoundKeyismatrixaddition.TheAddRoundKeytransformationistheinverseofitself65
2025/4/2AnIntroductiontoInformationSecurity2.3TheAESCipher:DecryptionDecryptionisthereverseprocess
ofencryptionRemarks:Sub-BytesS-boxforencryptionS-box-1fordecryptionMix-columnmatrixCfordecryptionmatrixC-1fordecryptionReverseroundkeys2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕66
2025/4/2AnIntroductiontoInformationSecurity2.4AESKeyExpansionTocreateroundkeysforeachround,AESusesakey-expansionprocess.IfthenumberofroundsisNr,thekey-expansionroutinecreatesNr+1128-bitroundkeysfromonesingle128-bitcipherkey.2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕67
2025/4/2AnIntroductiontoInformationSecurity2.4AESKey
Expansion2.AESAlgorithm3…
1…
Lecture6:AdvancedEncryptionStandard〔AES〕68
2025/4/2AnIntroductiontoInformationSecurityLecture7:BlockCipherModesofOperation2.1ECB2.2CBC2.3CFB2.4OFB2.5CTR2.BlockCipherModesofOperation1…
TheElectronicCodeBook(電子密碼本模式):simplestmodeEachblockofplaintextisencodedindependently(獨立地)usingthesamekeyPencryptKThefirstm-bitofPTime=1Thesecondm-bitofPTime=2Thesecondm-bitofCencryptKThenthm-bitofPTime=NThenthm-bitofCencryptKThefirstm-bitofCCAnyProblem?69
2025/4/2AnIntroductiontoInformationSecurityLecture7:BlockCipherModesofOperation2.1ECB2.2CBC2.3CFB2.4OFB2.5CTR2.BlockCipherModesofOperation1…
TheElectronicCodeBookCommentstoECBthesameblockofplaintext,ifitappearsmorethanonceinthemessage,alwaysproducesthesameciphertext.Cannotprev
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