第4章数据安全和完整

44.123IheardfromyourbrothelinNewOrleansPlantomeettheretomorrowIheardfromyourbrotherinNewOrleansPlantomeettheretomorrowbrotherrASCII11100104100101101101101l5CATV4.24.44.54.64.2ParityChecking11ParityBit111104-11401514.2.1164Kbps()640BurstError01111011150504.2.24-2135724681484-101114-24.44.2.3()4-325104-31064-34149182,4,681,3,57*1504-3405ijijj1/2in(1/2)nnn=20(1/2)20=1/104856799.99994.3CRC,CyclicRedundancyCheckCRCbn1bn-2bn3b2b1b0bn1xn1+bn2xn2+bn3xn-3++b2x2+b1x1+b010010101110x10+x7+x5+x3+x2+x1bi01bi10CRC210004151BB(x)B2B(xG(x)(GeneratorPolynomial)R(x)3T(x)=B(x)R(x)T(x)/G(x)0R(x)04T(x)T5TT(x)T(x)G(x)0TT()()T(x)G(x)24.3.14-4T(x)/G(x)T(x)=x10+x9+x7+x5+x4G(x)=x4+x3+14-4x10+x9+x7+x5+x4)/(x4+x3+1)220001010111100001010111102CRC1524-520x10+x9+x7+x5+x411010110000x4+x3+x1110014.3.2CRCCRC1101011G(x)=x4+x3+1Gx00411010110000B(x)G(x)4-44-5R(x)=x3+x1010Q(x)B(x)=G(x)Q(x)+R(x)T(x)=B(x)R(x)11010110000101011010111010TB0R4-6B(x)G(x)=Q(x)+R(x)G(x)4-5(x10+x9+x7+x5+x4)/(x4+x3+1)24-6T(x)G(x)4-7G(x)12345674153T(x)G(x)0TTG(x)0T40110000010102G(x)04-70G(x)G(x)4.3.3CRCCRCG(x)0TG(x)0CRCTT(x)T'T'(x)T(x)=T(x)+E(x)E(x)T=11010111010T(x)x10+x9+x7+x5+x4+x3+xE=00010110000E(x)=x7+x5+x4T=11000001010T'(x)=x10+x9+x3+xE(x)T(x)x7x7+x7=(1+1)x7=0(T(x)+E(x))/G(x)0(T(x)+E(x))/G(x)=T(x)/G(x)+E(x)/G(x)0E(x)E(x)/G(x)0G(x)E(x)G(x)E(x)?TE(x)xkkG(x)xkG(x)xG(x)CRCkr=G(x)T(x)tntn-1...ti+k-1ti+k-2...titi-1...t1t0kti+k-1tiE(x)=xi+k1++xi=xi(xk1++1)G(x)xG(x)G(x)xG(x)xk1++1krE(x)G(x)=xi×(xk-1++1)G(x)pqrpqprq8/32823xk1rG(x)xG(x)G(x)E(x)E(1)11x+1G(x)G(x)G(x)=(x+1)H(x)H(x)G(x)E(x)G(x)(x+1)H(x)E(x)=(x+1)H(x)K(x)x=1x+1E(1)0E(1)1x+1G(x)x+1G(x)G(x)k1rG(x)G(x)(xk1++1)k1rG(x)rG(x)(xr++1)G(x)=(xr++1)1r1r1G(x)1/2r112r1k1r1/2r[Pe72][Mo89]CRCG(x)CRC-12x12+x11+x3+x2+x+1CRC-16x16+x15+x2+1CRC-ITUx16+x12+x5+1CRC32x32+x26+x23+x22+x16+x12+x11+x10+x8+x7+x5+x4+x2+x+1G(x)CRCG(x)xx+1CRCrG(x)(2r-11)/2r-1r+1(2r1)/2rr+1(CRC32(2321)/2323399.99999998)4.3.4CRCCRCE(x)G(x)=xi×(xk-1++1)G(x)15441554-72CRCG(x)G(x)=brxr+br1xr1++b2x2+b1x+b0bi01i=0,,rrb0br1xr1•bi1•••4-8G(x)=x4+x3+1x31x2x04-84-704-7114-711100001010765432104-74-74-87CRC4.44.4.1R.W.HammingHammingCodeRAMm1m2m3m4m5m6m7m83nn4-18n416481213124-1nn2n1922104311841216p1p2p3p44-915641571121343414b1b2b3b4pibi=0bi=1i=1,2,344-244-244-2b1b2b3b400001p100012p200103p1p200114p301005p1p301016p2p301107p1p2p301118p410009p1p4100110p2p4101011p1p2p4101112p3p411004-10011001110101110101114-11010101010111p1p3135791145671214-255014-921p44,8,9,10,11,12p34,5,6,7,12p22,3,6,7,10,11p11,3,5,7,9,114.4.2[Ko78][Ha80]4.4.3LANNASA1584-110101=51001p4p3p2p14-1041594.54-124-121234567891234567894-13160EncryptionDecryptionPlaintextCiphertext4-13PCC=Ek(P)EkCCP=Dk'(C)Dk'P=Dk'(Ek(P))k=k'4.5.1MonoalphabeticCipherCaesarCipherASCII1ABBC4-13ASCII1ASCIIETOANQZ4-13{;RSDR\SFF\,PMRU\YP\,U\NSML\SVVPIMY\$234567890\(7)S(4)RPM(3)ETOAN{;D\FF\,U\Y\,U\NL\VVIY\$234567890\{;DFF,UY,UNLVVIY$234567890YFFO3ATYDF4161{;D,U,UNLVVIY$234567890HangmanWheelofFortune4.5.2PolyalphabeticCipher4-140AZBZAi0jVV[(imod26),j]4-15CTHE25541044-3THESHFVKITIG025243214-14Vigenre4-15Vigenre/**//**//*Vigenere*/fori=0/*P[i]*//*C%*/ASCII1624-3i=iMOD26jT252519SH2607HE2714FT54219VH5537KE5644IT104019TH10517IE10624GVigenreSHFTIGTIGSHFTHETHE26ASCIISHTIVKASCII114-14ZA26262626!410264.5.3TranspositionCiphermm1m21mp1,p2,pmp1ppm4-4MISSPIGGYKERMITANDFOZZIEBEAR2,4,3,1,5243154-412345MISSPIGGYKERMITANIMALANDFOZZIEBEARIIKTMNZBSGRALIASGEADZEMPIIAOYMNFER24315THEINGIS4.5.44-16pi⊕/i010pi⊕0⊕0pi⊕0pi1pi⊕1⊕1pi⊕1⊕1pi⊕0pipi4.5.541634-16164IBM2070DataEncryptionStandard,DES1977VLSIDES64566464194-176456163232644-1816K5656X4848X4-17DES1656644165DESC646432L3232R32R3248R48R3256K56R46K5648X48X4886X664X4843232L32X32R3232X323264X56X484-18DES165648C64=64L32=C6432R32=C6432K56=566448632R3232X323264166IBM1664Cbvoidtransposition(sometypeb[N],intt[N])/*b*//*t0N1*/{sometypetemp[N];/*b*/inti;/**/for(i=0;iN;i++)/**/temp[i]=b[i];for(i=0;iN;i++)/*it[i]temp*/b[i]=temp[t[i]];}[St95a][St95b]DESDES6464DES[Ko77]DESIBM128NationalSecurityAgency,NSA565656128DES256≈71016DESNSADESDESDESNSA[Sh77]4.5.61993(ClipperChip)Clippercapstone41674-194-19NSA[Si96]SkipJackSkipJackAlgorithmNSA1987NSAFBIDiffie-Hellman•K80•F80•N30•S80SEkEF(ES(K)+N)4-204-20DFES(K)+NFDSSSSS=S1⊕S2⊕S1S2KeyEscrowAgencies80S1S2S=S1⊕S2S1NS2NSS1S2SS1S2SDSES(K)KEK168EEEs(K)+NEs(K)NDFNS1S2S=S1⊕S2DSES(K)K124169[De96]4.5.7KeyDistributionorExchange4.5.8Merkle[Me78]Puzzle1)n2)3)ID4)IDn4.5.9ShamirShamirkkkkk1kShamir[Sh97]p(x)=a0+a1x+a2x2++ak1xk1k-1(x1,y1)(x1,y2)(xk,yk)p(x)xixjijp(x)a0,a1,ak1Shamirp(x)a0p(x)xkkkaiShamir4.5.10Diffie-HellmanDiffie-Hellmangn4-21AB4-21Diffie-HellmanAxgxmodnBBygxmodnAgnAgymodnxgyxmodnBgxmodnygxymodngyxmodngxymodnABgngxmodngymodnABxygngxmodngymodnxygxmodngymodnnggn[Sc94][St95a]170gxmodngxmodnxK=gyxmodnyK=gxymodng,n,gxmodn,gymodnK41714.6EKDK'ASCIIkASCIIkVigenreEK1976DiffieHellman[Di67]4-22EKDK'EKDK'EK4-22PublicKeyCryptosystemNovellNetware4.04.6.1RSARSARivestShamirAdleman[Ri78]EK[St95a]RSA1126AZ2nnpq1200n=pq=117=773kk(p1)(q1)1Ek(A)Ek(B)172k=7(p1)(q1)=106=60kk4HELLOHELLO5851212156kn87mod7757mod77127mod7