What is revocation (Widerruf), and what are CRL and OCSP?

Revocation is the process of declaring permissions, authentication means, digital certificates, verifiable credentials or similar invalid, so that the element is no longer trusted or usable; a certificate revocation list is a CA-published list of certificates revoked before their expiry (serial number and time of revocation), and the Online Certificate Status Protocol lets a client query the validity status of a single certificate.

Examples of revocation: an issuer revoking certificates or VCs, an RP withdrawing a permission, invalidating compromised API tokens or OTP devices, revoking active session tokens after an incident. Synonyms: Revokation, Sperrung.

Go deeper:

• Certificate revocation list (Wikipedia) — format, distribution and the freshness problem of published lists.
• OCSP (Wikipedia) — querying one certificate's status online, including OCSP stapling.