Nonces are described as usable in which type of applications according to the material?

• A. All applications
• B. Client/server applications
• C. Time-insensitive applications
• D. Persistent applications

Answer: (B)

Nonces are used to ensure freshness in a communication, preventing replay of old messages. In a client/server interaction, a nonce can be issued by one side (usually the server) and must be included in the response by the other side, tying the reply to that specific, current exchange. This challenge-response pattern is a hallmark of client–server authentication and secure exchanges, which is why nonces are described as usable in client/server applications.

Why this fits better than the other options: the need for a one-time fresh value is not inherent to all applications, nor is it a feature of time-insensitive or long-lived, persistent interactions. These contexts don’t rely on replay-prevention in the same way, so the described use of nonces aligns with client/server communications where freshness and timely responses are essential.