How is the message digest created by the supplicant?

• A. Adding the password to the challenge message and hashing the two
• B. Hashing the plaintext message
• C. Encrypting the message digest with its own private key
• D. None of the above

Answer: (B)

The idea being tested is that a message digest is produced by applying a cryptographic hash function to the message itself. You take the plaintext message and run it through a hash function (like SHA-256) to produce a fixed-length digest. This digest serves as a compact fingerprint of the message: if the message changes, the digest changes with extremely high probability, enabling integrity verification.

Hashing the plaintext directly matches this concept because it describes generating the digest from the exact data being sent. The other options mix in passwords or involve encrypting the digest with a private key, which would be procedures for authentication or digital signing, not the creation of the digest itself.