Readingfunction
Incryptography:secretkey-secretkey;privatekey-privateKey;publickey-publickey.Key(yào)key,keyistheabbreviationofsecretkey.
Keyclassification
Keysaredividedintotwotypes:symmetrickeysandasymmetrickeys
Twotypesofkeys
Accordingtowhethertheencryptionkeyanddecryptionkeyusedbythecryptographicalgorithmarethesame,whetherthedecryptionprocesscanbederivedfromtheencryptionprocess(ortheencryptionprocesscanbederivedfromthedecryptionprocess),thecryptosystemcanbedividedintosymmetricalCryptography(alsoknownassinglekeycryptography,secretkeycryptography,symmetrickeycryptography)andasymmetriccryptography(alsoknownasdualkeycryptography,publickeycryptography,andasymmetrickeycryptography).
SymmetryKeyEncryption,alsoknownasprivatekeyencryptionorsessionkeyencryptionalgorithm,thatis,thesenderofinformationUsethesamekeyasthereceivertoencryptanddecryptdata.Itsbiggestadvantageisfastencryption/decryptionspeed,suitableforencryptinglargeamountsofdata,butkeymanagementisdifficult.
Asymmetrickeyencryptionsystem,alsoknownaspublickeyencryption.Itneedstousedifferentkeystocompletetheencryptionanddecryptionoperationsrespectively.Oneispubliclyreleased,thatis,thepublickey,andtheotheriskeptsecretbytheuser,thatis,theprivatekey.Themessagesenderusesthepublickeytoencrypt,andthemessagereceiverusestheprivatekeytodecrypt.Thepublickeymechanismisflexible,butthespeedofencryptionanddecryptionismuchslowerthanthatofsymmetrickeyencryption.
Soinactualapplications,peopleusuallycombinethetwotogether.Forexample,asymmetrickeyencryptionsystemisusedtostorealargeamountofdatainformation,andapublickeyencryptionsystemisusedtoencryptkeys..
Forordinarysymmetriccryptography,encryptionoperationsanddecryptionoperationsusethesamekey.Generally,thesymmetricencryptionalgorithmusedisrelativelysimpleandefficient,thekeyisshort,anditisextremelydifficulttodecipher.Sincetheconfidentialityofthesystemmainlydependsonthesecurityofthekey,itisimportanttotransmitandkeepthekeysecurelyonanopencomputernetwork.Seriousproblem.Itispreciselybecausebothpartiesusethesamekeyinsymmetriccryptographythatfunctionssuchasdatasignatureandnon-repudiationcannotberealized.
Sincethe1970s,somescholarshaveproposedapublickeysystem,whichusesthemathematicalprincipleofaone-wayfunctiontorealizetheseparationofencryptionanddecryptionkeys.Theencryptionkeyispublic,andthedecryptionkeyisconfidential.Thisnewcryptosystemhasarousedwidespreadattentionanddiscussionincryptographycircles.
Unlikeordinarysymmetriccryptographythatusesthesamekeytoencryptanddecryptdata,asymmetrickeyencryptiontechnologyusesapairofmatchingkeysforencryptionanddecryption.Therearetwokeys,oneItisapublickeyandtheotherisaprivatekey.Theyhavethisproperty:eachkeyperformsaone-wayprocessingofdata,andthefunctionofeachkeyisexactlytheoppositeoftheother.Whenoneisusedforencryption,theotherisItisusedfordecryption.Filesencryptedwiththepublickeycanonlybedecryptedwiththeprivatekey,andfilesencryptedwiththeprivatekeycanonlybedecryptedwiththepublickey.Thepublickeyismadepublicbyitsowner,whiletheprivatekeymustbekeptsecret.Inordertosendaconfidentialmessage,thesendermustusethereceiver'spublickeytoencryptthedata.Onceencrypted,onlythereceivercandecryptitwithitsprivatekey.Conversely,userscanalsousetheirownprivatekeystoprocessdata.Inotherwords,thedirectionoftheworkofthekeypairisoptional.Thisprovidesthebasisfor"digitalsignature".Ifauseruseshisownprivatekeytoprocessthedata,otherscanusethepublickeyprovidedbyhimtoprocessthedata.Sinceonlytheownerhimselfknowstheprivatekey,thisprocessedmessageformsakindofelectronicsignature-adocumentthatcannotbeproducedbyothers.Thedigitalcertificatecontainspublickeyinformation,therebyconfirmingtheidentityoftheuserwhoownsthekeypair.
Asimpleexampleofapublickeycanberepresentedbyaprimenumber.Thealgorithmformultiplyingprimenumbersisusedasthepublickey,andthealgorithmforsolvingthemultiplicationintegralintotheoriginalprimenumberistheprivatekey.EncryptioniswhatyouwanttotransmitTheinformationisencodedwithprimenumbersandtransmittedtotherecipientafterencoding.Ifanyonereceivesthisinformationwithouttheprivatekeyownedbytherecipient,thedecryptionprocess(actuallytheprocessoffindingprimenumbers)willbeduetoTheprocessoffindingprimenumbers(decomposingprimefactors)takestoolongtointerprettheinformation.