密码学Digital Signature

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1、DigitalSignature曹天杰TianjieCaotjcao@cumt.edu.cnCollegeofComputerScienceandTechnology,ChinaUniversityofMiningandTechnology,Xuzhou,China中国矿业大学计算机科学与技术学院2003.6.61DefinitionsDefinitionsDigitalSignature-adatastringwhichassociatesamessagewithsomeoriginatingentityDigi

2、talSignatureGenerationAlgorithm–amethodforproducingadigitalsignatureDigitalsignatureverificationalgorithm-amethodforverifyingthatadigitalsignatureisauthentic(i.e.,wasindeedcreatedbythespecifiedentity).DigitalSignatureScheme-consistsofasignaturegenerationalgori

3、thmandanassociatedverificationalgorithm2ApplicationsDigitalSignaturescanprovideAuthenticationDataIntegrityNon-RepudiationOneApplicationCertificationofpublickeysinlargenetworks3ClassificationDigitalsignatureschemeswithappendixrequiretheoriginalmessageasinputtot

4、heverificationalgorithm.Digitalsignatureschemeswithmessagerecoverydonotrequiretheoriginalmessageasinputtotheverificationalgorithm.Inthiscase,theoriginalmessageisrecoveredfromthesignatureitself.4Classification(cont)Taxonomyofdigitalsignaturessignatureschemesmes

5、sagerecoveryappendixdeterministicrandomizedrandomizeddeterministic5TypesofSignaturesDirectdigitalsignature–involvesonlythecommunicatingpartiesAssumedthatreceiverknowspublickeyofsender.Signaturemaybeformedby(1)encryptingentiremessagewithsender’sprivatekeyor(2)e

6、ncryptinghashcodeofmessagewithsender’sprivatekey.Furtherencryptionofentiremessage+signaturewithreceiver’spublickeyorsharedprivatekeyensuresconfidentiality.6TypesofSignaturesProblemswithdirectsignatures:Validityofschemedependsonthesecurityofthesender’sprivateke

7、ysendermaylaterdenysendingacertainmessage.PrivatekeymayactuallybestolenfromXattimeT,sotimestampmaynothelp.7TypesofSignaturesArbitrateddigitalsignature–involvesatrustedthirdpartyorarbiterEverysignedmessagefromsender,X,toreceiver,Y,goestoanarbiter,A,first.Asubj

8、ectsmessage+signaturetonumberofteststocheckorigin&contentAdatesthemessageandsendsittoYwithindicationthatithasbeenverifiedtoitssatisfaction8ArbitratedDigitalSignaturesRequiresanunco