Q19Information Security Systems
Question
Explain the X.509 digital certificate format. Detail the components of Public Key Infrastructure (PKI) and their interactions.
Answer
X.509 defines the format for digital certificates within a Public Key Infrastructure (PKI).
The X.509 standard dictates the structure and contents of a digital certificate, which is used to bind an entity's identity to their public key. An X.509 certificate includes fields such as Version, Serial Number, Signature Algorithm ID, Issuer Name, Validity Period, Subject Name, Subject Public Key Info, and standard extensions. It is digitally signed by a trusted third party.
Public Key Infrastructure (PKI) is the overarching framework managing these certificates. Key components of PKI include:
1. Certificate Authority (CA): The highly trusted entity that issues, signs, and manages digital certificates. It vouches for the identity of the certificate holder.
2. Registration Authority (RA): A subordinate entity that verifies user identities and approves certificate requests before passing them to the CA.
3. Certificate Repository: A centralized directory where certificates and Public Keys are stored and accessible to users.
4. Certificate Revocation List (CRL): A list maintained by the CA detailing certificates that have been revoked prior to their expiration date.
