For message-by-message authentication, does each message need an electronic signature?

• A. True
• B. False
• C. Only for special messages
• D. Not necessary

Answer: (A)

Per-message authentication requires proving the origin and integrity of each distinct message. A digital signature binds the signer to the exact content of the message, so every individual message can be verified as authentic and unaltered. If only some messages are signed or a batch is signed, messages outside that signed set aren’t protected, leaving them vulnerable to forgery or tampering. Signing every single message ensures that for each piece of data that arrives, you have a verifiable authorship and integrity check. While some systems use signed batches or rely on other mechanisms for efficiency, those approaches don’t provide per-message signing by default. So, to achieve true per-message authentication, each message should be signed.