In addition to the user's identifier, the user's public key and the CA's identifier, an X.509 certificate includes several other elements. The certificate contains an identifier of the algorithm used to sign the certificate and the period of validity of the certificate. The latest version of the standard, X.509v3, also includes an extensions field to provide more flexibility and to convey information needed in special circumstances. Finally, X.509 provides a format for use in revoking a key before it expires. This enables a user to cancel a key at any time.
Stallings is a consultant, lecturer and author on data communications and networking topics.
This article is based on material in his most recent book, Cryptography and Network Security. Some companies are hoping you would. Experts Exchange Get answers to your networking questions. Inc. All rights reserved.