A digital ________, by itself, provides authentication.

• A. signature
• B. certificate
• C. Both A and B
• D. Neither A nor B

Answer: (D)

Authentication is about proving who someone is. A digital signature on a message shows that the signer had the private key and that the message hasn’t been altered, but it doesn’t by itself prove the signer’s identity unless you already trust that the key belongs to that person. A digital certificate binds a public key to an identity, but on its own it doesn’t authenticate you; you must validate the certificate against a trusted authority, check its validity period, revoke status, and ensure you trust the issuing CA. In short, neither a signature nor a certificate alone establishes authentication without additional trust and verification steps.