Resource PKI: Certificate Policy & Certification Practice Statement Dr. Stephen Kent Chief Scientist - Information Security Terminology Certificate: a digitally-signed data structure typically an X.509 public key certificate (PKC), the certificate standard adopted by the IETF and employed in SSL/TLS, IPsec (IKE), S/MIME, and many other IETF security protocol standards Certification Authority (CA): an entity that issues (digitally signs) certificates, aka an Issuer