A CRL is comprised of.
Malicious IP addresses.
Untrusted private keys.
A certificate revocation list (CRL) is created and distributed to all CAs to revoke a certificate or key.
By checking the CRL you can check if a particular certificate has been revoked.
The certificates for which a CRL should be maintained are often X.509/public key certificates, as this format is
commonly used by PKI schemes.