Which of the following is a defence against enemy deception?

• A. Authentication
• B. Good procedures
• C. Constant vigilance
• D. Encryption

Answer: (A)

Authentication defends against enemy deception by confirming who is sending a message and that it originates from a trusted source. Using methods like shared secrets, call signs, challenge-response, or digital signatures lets the receiver verify identity and reject impersonations or spoofed commands. Good procedures help reduce the opportunities for deception, but they don’t on their own prove who is talking. Constant vigilance is important for spotting anomalies, yet without a mechanism to verify identity, deceptive signals can still appear legitimate. Encryption protects the content of a message from being read by others, but it doesn’t by itself verify who sent it (unless paired with authentication mechanisms like digital signatures).