Patent ID: 8635442

Claim:
A computer-implemented method, comprising: receiving, by a computing device, a digital signature of data and of a signing time of the digital signature; receiving, by the computing device, a first digital certificate comprising information for verifying the digital signature, wherein the first digital certificate has an expiration time; receiving, by the computing device, a current certificate revocation list (CRL) issued by a certificate authority after expiration of the first digital certificate, the CRL comprising revocation information for a plurality of revoked digital certificates including expired digital certificates, wherein the revocation information is up to date as of the time of issuance by the certificate authority, wherein at the time of issuance by the certificate authority the revocation information of the CRL indicates whether the expired first digital certificate has been revoked and indicates a revocation time if the expired digital certificate has been revoked; and subsequent to the expiration time of the first digital certificate, determining, by the computing device, that said digital signature is valid, wherein said determining comprises evaluating the CRL to determine that the first digital certificate was not revoked at said signing time.