What is a Certificate Revocation List (CRL)?

A Certificate Revocation List (CRL) is specifically a list of certificates that have been revoked by a Certificate Authority (CA) before their scheduled expiration date. This revocation can occur for several reasons, such as the compromise of a private key, the expiration of the certificate holder's association with the organization, or the change in the status of the certificate holder. The CRL serves as an essential component of the Public Key Infrastructure (PKI) ecosystem, ensuring that clients and users can verify the status of certificates and maintain secure communications. By checking the CRL, entities can avoid trusting certificates that are no longer valid, which helps prevent unauthorized access and enhances overall security within the network.

The other choices do not accurately represent the function of a CRL. For instance, while losing access rights is a concern for users within a system, it does not pertain to the revocation of digital certificates. Similarly, a list of network servers and their statuses or pending certificate applications would not provide information relevant to the status of already issued certificates and their validity.