In public key encryption for authentication, the verifier decrypts the ciphertext with the verifier's public key.

• A. True
• B. False
• C. Only for certain algorithms
• D. Not applicable

Answer: (B)

Public key cryptography used for authentication relies on digital signatures. In this approach, the signer creates a signature on a message (or challenge) using their private key. Anyone with the signer’s public key can then verify that signature to confirm who signed and that the message hasn’t been altered. Decryption with a public key isn’t part of this process—the decryption step uses the private key, not the public key. So the verifier doesn’t decrypt a ciphertext with the public key; they verify a signature with the signer’s public key. That’s why this statement is false.