科技英语文献阅读与翻译Unit 1-TextB.ppt

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1、UnitOneTextBDigitalSignatureinAppliedCryptographyBackgroundInformation7/25/20212UnitOneTextBDigitalSignatureinAppliedCryptographycryptographyCryptographyisthestudyofmathematicaltechniquesrelatedtoaspectsofinformationsecuritysuchasconfidentiality,dataintegrity,entityauthentication,anddataorigi

2、nauthentication.AstheInternetandotherformsofelectroniccommunicationbecomemoreprevalent,electronicsecurityisalsobecomingincreasinglyimportant.Cryptographyisusedtoprotecte-mailmessages,creditcardinformation,andcorporatedata.7/25/20213UnitOneTextBDigitalSignatureinAppliedCryptographypublickeyIti

3、sthekeyforusewithpublickeyencryptionmethodsthatispubliclymadeavailable.Itispublishedbythekeyholderortheissuingcertificationauthority.Thecertificationauthority’sdirectoryservercandistributeitbydisk,webdownloadore-mail.Thepublickeycanbecertifiedusinganelectroniccertificateissuedandsignedbyacert

4、ificationauthority.7/25/20214UnitOneTextBDigitalSignatureinAppliedCryptographyprivatekeyItisthekeyforusewithasymmetricencryptionthatisaccessibletothekeyholderonly.Asymmetricencryptionusesdifferentkeysforencryptionanddecryption.Eachparticipantisassignedapairofkeys,consistingofanencryptionkeyan

5、dacorrespondingdecryptionkey.Aprivatekeyisusedforgeneratingdigitalsignaturesandfordecryptingdata.7/25/20215UnitOneTextBDigitalSignatureinAppliedCryptographyhashfunctionandhashvalueHashFunctionisanalgorithmthattransformsastringofcharactersintoausuallyshortervalueofafixedlengthorakeythatreprese

6、ntstheoriginalvalue.Thisiscalledthehashvalue.Hashfunctionsareemployedinsymmetricandasymmetricencryptionsystemsandareusedtocalculateafingerprint/imprintofamessageordocument.7/25/20216UnitOneTextBDigitalSignatureinAppliedCryptographyhashfunctionandhashvalueWhenhashingamessage,themessageisconver

7、tedintoashortbitstring--ahashvalue--anditisimpossibletore-establishtheoriginalmessagefromthehashvalue.Ahashvalueisuniqueinthesensethattwomessagescannotresultinthesamebitstring,andanyattempttomakechangestothemessagewillnegatethevalueandthusthe