数据加密外文翻译Word格式.docx
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数据加密外文翻译Word格式.docx
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2.Maintainthehashingfunctionoriginalperformance,butdoesnotcauseitsdegeneration.
3.Causereasonablybasedonaboutfirstfloorhashingfunctionsuppositionmessagediscriminationmechanismencryptionstrengthanalysis.
4.Whendiscoverseitherneedstheoperatingspeedisquickerorthesaferhashingfunction,mayveryeasyrealizethefirstfloorhashingfunctionreplace.
[Annotation]:
Whencompbookdocuments,MD5andSHA-1areusethemostwidespreadencryptiontousethehashingfunction.
SecondHMACalgorithmprinciples
2.1HMACalgorithmdefinition:
Expressesasfollowswiththeformula:
HMAC=H(keyoropad,H(keyoripad,text))
H(X,Y)expressioncarriesononekindofHashoperationtoX+Ynews.
RepresentativeIpadisredundantBtimesinglebytehexadecimalsystemsystemconstantOX36;
RepresentativeOpadisredundantBtimesinglebytehexadecimalsystemconstantOX5C;
keyrepresents64bytesstringsofcharacter,iscomposedofthekey,insufficientmakesup0;
Textrepresentstherandomlengthtext;
Keylength≥Lbyte.WhenisbiggerthanB,passesthroughtheHashcomputationtoformLbytePerukey(BisfirstintheHashalgorithmaniterativecomputationblockdatabytecount;
ListheHashalgorithmformsthetextabstractthebytecount,inMD5isin16,SHA-1is20).
2.2Algorithmstep
(1)IncreasesbehindkeyK0foundsawordlengthistheBstringofcharacter.(e.g.,iftheKwordlengthis20bytes,B=60byte,thenafterK,willjoin44zerobyte0x00),iftheKlengthwillbebiggerthantimeB,shouldundergohashingfunctionprocessing.
if(key_len>
64)
{MD5_CTXtctx;
MD5Init(&
tctx);
MD5Update(&
tctx,key,key_len);
MD5Final(tk,&
key=tk;
key_len=16;
}
(2)OnonestepwillproducetheBwordlength'
sstringofcharacterandipadmakethe"
orelse"
.k_ipad[i]^=0x36;
(3)Fillsdatastreamtexttothesecondstepresultstringofcharacter.
(4)AffectswithHinthedatastreamwhichthirdstepproduces.
transferhashingfunction(MD5,SHA-1)
(5)TheBwordlengthstringofcharacterwhichandopadfirststepproducesdoesthe"
.k_opad[i]^=0x5c;
(6)Entersagainthefourthstepresultpackinginthefifthstepresult.
(7)AffectswithHinthedatastreamwhichsixthstepproduces,theoutputfinaloutcome.
2.3MD5algorithm
TheMD5algorithmbycirculatesmanytimestotherandomlengthnewstheiterativehashoperation,forms16Bytetextabstractfinally.Thisabstracthasuniquenesstothetext,maytaketheauthenticationcode.Undertargetcomputer'
scomputationspeed,thisabstractisdifficultywithexplains
(1)thetextfills
TheMD5algorithmrequestcarriesonthepackingtotherandomlengthtext,theconstitutionN×
64Bytenewsgrouping,Nisaninteger.Andeachgroupingpaddingdataisdivided2steps.First,thepackingcausesthedatapositionlengthexactlyfor(N×
64-8)theBytenumber,namelyintextvaliddatareplacement10x1,othermakesup0x0tosatisfytheaboverequest.Then,againonreplacement8bytes(64)beforetextdatalength(packing,bytecount).Thus,thedatabythepackingis64Byte(512bit)integralmultiple.Alsodivides164bytesub-groupings.
(2)initializationMD5parameter
The44byteshiftquantity(A,B,C,D)usefortotakethetextabstractthestartingvalue:
A=0x01234567B=0x89abcdefC=0xfedcba98D=0x76543210
(3)algorithm
TheMD5algorithmistothenewsgroupinginturniterativealgorithm.1sttimeoperatesthestartingvalueisABCD,eachiterativecomputation'
sresultwillreplacelaterABCDtotakethenexttimestartingvalue,altogetherwillundergoNtimeiterativecomputation,willobtainthisnewstextabstract.
2.4realizethestep
Thefirststep:
Increasesfills
Increasespaddingtocausethedatalength(bitisunit)themold512is448.Ifthedatalengthhappentoisthemold512is448,increases512tofillbit,i.e.fillstheintegeris1-512.Firstbitis1,otherare0completely.
Thesecondstep:
Makesuplength
Thedatalengthtransformationisthe64bitvalue,ifthelengthsurpassesthedatalengthscopewhich64bitcanexpress,thevalueretainsfinally64bit,increasesbehinddatawhichfillstofront,causesthefinaldataisthe512bitintegralmultiple.Isalsothe32bit16timeofintegralmultiples.InRFC1321,32bitiscalledword.
Thethirdstep:
Initializationvariable
Withto4variables,respectivelyisA,B,C,D,is32bitislong.Theinitializationis:
A:
01234567B:
89abcdefC:
fedcba98D:
76543210
Thefourthstep:
Dataprocessing
Firstdefines4auxiliaryfunctions:
F(X,Y,Z)G(X,Y,Z)H(X,Y,Z)I(X,Y,Z)
Inwhich:
X&
Yexpressesaccordingtothepositionand,X|Yexpressedthataccordingtothepositionor,not(X)expressedtakesaccordingtothepositioninstead.xorexpressesaccordingtothepositiondifferentor.inthefunctionX,Y,Zare32bit.definesthearraywhichneedstouse:
TheT(i),ivalue1-64,T(i)wasequaltothatabs(sin(i))4294967296timeofintegralpart,iisaradian.
Afterthesuppositionfirstthreestepprocessingdatalengthis32*16*Nbit
Thefifthstep:
Output:
ObtainsfinallyABCDistheoutputresult,altogether128bit.Aisthelowposition,Disatopdigit.
ThirdKey
UseinHMACthekeybeingpossibletobetherandomlength(keywhichwillbelongerthanBfirstbytheHprocessing).ButwhenthekeylengthissmallerthantheLsituationisdisappointing,becauselikethiswillreducethefunctiontheworkingstrength.ThelengthisbiggerthanLthekeyisacceptable,buttheextralengthcannotremarkableenhancethefunctiontheworkingstrength.(ifastochastickeywereconsideredthatisunreliable,thenchoosesalongkeyisunwise).Thekeymustselect(orusestochasticallyformidablebasedonstochasticseed'
spseudo-randomproductionmethod),andwantstheperiodicrenewal.(thepresentattackhasnotpointedoutaneffectivereplacementkey'
sfrequency,becausetheseattacksarenotinfactfeasible.However,theperiodicrenewalkeyisonelatentdefectbasicsecuritymeasurewhichcopeswiththefunctionandthekeyexists,andmayreducedivulgestheharmwhichthekeybrings.)
Forthmattersneedingattention
HMACismaynotrevisethesoundcodeaccordingtothefirstfloorhashingfunctiontobepossibletousethiswaytodefine.EspeciallyitwhenusestheHfunctionmustrelyonthepre-definitioninitializationvalueIV(adefinitevalue,byeachiterationhashingfunctionwheninitializationitscompressionfunctionassigns).However,ifyouwant,mayrevisetheHfunctionthesoundcodetosupportinvariableinitializationvalueIvs.
Thisideaisthis:
Thecompressionfunctiontheintermediateresultwhich(KXORopad)and(KXORipad)producesintheBwordlengthblockdatamaywhenthekeyjustproducedinadvancecalculateswell.Savesfirsttheseintermediateresults,thenwheneachtimehasthenewsneedstoconfirmproducestheHfunctiontheinitializationvalueIV.ThismethodmustdistinguishthenewswhichhaspreservedtheHcompressionfunctionregardingtwoBwordlengthblockdata(KXORopad)and(KXORipad)theapplicationforeach.Whendistinguishestheshortdatastream,preservessuchinformationisimportant.Whatwemuststress:
Treatstheseintermediateresultstotreatthekeytobethesamelikely,andwantssametocarryonthesecurity.
TheabovechoicerealizestheresultwhichtheHMACmethodislocalcarriesout,tointernaloperationalhasnotaffected
Fifthsafe
Herewillexplainthatthemessagediscriminationmechanismthesecurityisdecidedbythehashingfunctionencryptioncharacteristicwhichuses:
1.Anti-conflictattackcapability(isrestrictedininitializationvalueisonlystochastic,andsecret,andfunctionoutputtoaggressorisnotavailablesituation)2.TreatsasuseswhenthesingleblockdatatheHcompressionfunctionthemessagediscriminationattribute(inHMACtheseblockdataispartunknown,whenaggressorself-restraintinteriorHfunctionalcalculusresult,andaggressorcannotfullchoice)
InHMACusesabovethehashingfunctionhasorastrongerattributegenerally.Infact,ifahashingfunctiondoesnothaveaboveattributethatitnottobesuitableregardingthemajorityencryptionapplicationprocedure,includingbasedonthisfunctionchoicemessagediscriminationplan.(seealso[BCK1]toHMACf
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