During signature verification, which step helps confirm the signature validity?

• A. Decrypt the signature with the sender's public key to obtain the digest
• B. Hash the message to obtain its digest
• C. Both A and B
• D. Neither

Answer: (B)

Verification hinges on proving that the signed digest and the digest you compute from the message are the same. To do this, you hash the message to produce its digest, then decrypt the signature with the sender’s public key to recover the digest that was originally created during signing. If these two digests match, the signature is valid, the message hasn’t been altered, and the signer possesses the corresponding private key. Hashing the message alone helps prepare the value to compare, but you must also decrypt the signature to confirm it actually came from the claimed signer.