Certificatesare()documentsattestingtothe()ofapublickeytoanindividualorotherentity.Theyallowverificationoftheclaimthatagivenpublickeydoesinfactbelongtoagivenindividual.Certificateshelppreventsomeonefromusingaphonykeyto()someoneelse.Intheirsimplestform,Certificatescontainapublickeyandaname.Ascommonlyused,aCertificatealsocontainsan(请作答此空)date,thenameoftheCAthatissuedtheCertificate,aserialnumber,andperhapsotherinformation.Mostimportantly,itcontainsthedigital()ofthecertificateissuer.ThemostwidelyacceptedformatforcertificatesisX.509,thus,CertificatescanbereadorwrittenbyanyapplicationcomplyingwithX.509.
A.communication
B.computation
C.expectation
D.expiration
正确答案是D