Which of the following processes of PKI (Public Key Infrastructure) ensures that a trust relationship exists and that a certificate is still valid for specific operations?

Certificate issuance is the process by which a CA creates and distributes a new certificate to a requester - it establishes the certificate but does not verify an existing one's ongoing validity.

Certificate validation verifies the full chain of trust by checking that the certificate is signed by a trusted CA, that the chain leads to a trusted root, that the certificate has not expired, and that it has not been revoked via CRL (Certificate Revocation List) or OCSP (Online Certificate Status Protocol). This process is what ensures both the trust relationship and the current operational validity of the certificate.

Certificate cryptography is not a defined PKI process - it loosely describes the cryptographic algorithms embedded in certificates rather than any specific lifecycle operation.

Certificate revocation is the act of invalidating a certificate before its natural expiry, which is only one factor checked during the validation process, not the validation process itself.