What information is contained in a Certificate Revocation List (CRL)?

A Certificate Revocation List (CRL) is specifically designed to list certificates that have been revoked before their designated expiration dates. This is crucial for maintaining security in environments where digital certificates are used for encryption and authentication.

Revocation can occur for a variety of reasons, including compromised private keys, a change in the affiliation of a certificate holder, or the finding that the certificate was issued erroneously. The CRL effectively informs all parties relying on certificates (such as browsers, applications, and network services) which certificates should no longer be trusted, enhancing the overall integrity of cryptographic communications.

The other choices pertain to different states of certificates: expired certificates are those that have outlived their validity period, valid certificates are currently in effect, and pending certificates refer typically to those that are awaiting final assignment or approval. However, none of these categories represent certificates that have been actively revoked, which is the primary and critical role of the CRL.