A TLS server, an S/MIME client and a code-signing verifier all parse the same certificate structure. Which standard defines that structure?
A TLS server, an S/MIME client and a code-signing verifier all parse the same certificate structure. Which standard defines that structure?
Answer
X.509
Options - A. X.509 - B. PKIX - C. ASN.1 - D. IETF Why - A. Correct. X.509 defines the certificate structure itself, and RFC 5280 profiles it for the Internet. - B. The sharp distractor, because it is genuinely adjacent. PKIX is the IETF working group and the *profile* of X.509 for the Internet — a set of usage choices, not the format. - C. ASN.1 is the abstract notation X.509 is *written in*, and DER is how it is encoded. Naming the notation is like answering "what format is this document" with "UTF-8". - D. The IETF is a standards body. It publishes profiles; it is not itself a certificate format. The discrimination is format versus profile versus notation versus body.
Stallings & Brown, Computer Security 5e, ch23 §23.2; RFC 5280; RFC 6960