Digital signatures are used for which type of authentication?

• A. Initial
• B. Message-by-message
• C. Both A and B
• D. Neither A nor B

Answer: (B)

The concept being tested is how digital signatures verify who sent each piece of data and ensure that it hasn’t been altered. A digital signature is attached to a specific message, and anyone receiving it can confirm the sender’s identity and the message’s integrity using the sender’s public key. Because this verification happens for every message in a conversation, digital signatures are best described as a tool for message-by-message authentication.

Initial authentication, by contrast, is about proving identity at the start of a session and is usually accomplished with credentials, tokens, or a handshake that may involve signatures as part of a protocol, but the primary role of signatures themselves is to authenticate each individual message as it’s received.