What is the direct result of checking a digital signature against the message?

• A. The plaintext is recovered
• B. The message digest computed from the message matches the one obtained via the signature
• C. The signature is decrypted to reveal the public key
• D. The sender's private key is revealed

Answer: (B)

Digital signature verification checks integrity and authenticity by using the signer's public key to recover a hash from the signature and then comparing it to a freshly computed hash of the message. When a signature is created, the signer hashes the message and encrypts that hash with their private key to form the signature. To verify, you hash the received message and decrypt the signature with the signer's public key to obtain the original hash. If these two hashes match, the signature is valid, meaning the message hasn’t been altered and the signature was produced with the corresponding private key.

The other options don’t reflect what actually happens: you don’t recover the plaintext from the signature, you don’t decrypt the signature to reveal the public key, and you don’t expose the sender’s private key during verification.