Certificate Revocation: The process of declaring a digital certificate as no longer valid before its scheduled expiration date. This can occur due to a number of reasons such as the certificate’s private key being compromised, the certificate being issued in error, or the certificate holder no longer requiring the certificate. The revocation is typically handled by the issuing Certificate Authority, and the status of the revoked certificate is updated in real-time on a Certificate Revocation List (CRL) or via an Online Certificate Status Protocol (OCSP) responder. Timely certificate revocation is critical in maintaining a secure digital environment as it prevents the use of invalid certificates, thereby protecting against unauthorized access and data breaches.