If a system trusts a CA, it can rely on the digital certificates issued by that CA to verify identities.

• A. True
• B. False
• C. Partially true
• D. Not sure

Answer: (A)

In PKI, a trusted CA acts as a trust anchor. A certificate the CA signs binds a subject’s identity to a public key, so a system that already trusts that CA can verify identities by validating the certificate: follow the certificate chain to the trusted root, verify the CA’s signature with its public key, ensure the certificate is currently valid (not expired), check revocation status, and confirm the certificate’s intended use matches the connection (for example, server authentication). When these checks pass, the certificate provides a trustworthy assertion of identity. In practice, this remains true, though it depends on the CA not being compromised and on proper revocation checks.