Quest ion 4 Suppose that Caeser and his generals have selected a secret random key k for a Caeser cipher. The key is unknown to the enemy. Caeser and his generals also agree that to use \"W\" to represent the message \"withdraw\" and \"A\" to represent the message \"Attack now!\" Caeser is a strong believer in being unpredictable and will ip an unbiased coin to make his decision (a fact which is known to the enemy). Formally, if we let X E {\"A\