1. Suppose that you are back in ancient Rome, and have intercepted a message containing the ciphertext EVIRE Suppose that you know the message was encrypted with the Caesar cipher. However, you do not know the key (which as you know is a number between 1 and 25). Suppose that you also know that the message was sent from Caesar to Marc Antony in order to set up a secret meeting at one of four possible locations; in other words, you know the plaintext is one of the following four possibilities: arena forum

hills river

1. Try decrypting the ciphertext with all 25 possible keys in order to determine where Caesar and Marc Antony will meet. What are plausible plaintext values for this ciphertext EVIRE, and what keys would have created that ciphertext values?

How would intercepting another ciphertext message (with unknown plaintext) encrypted with the same key possibly help you determine which key is the correct one? Hint 1: This is related to a general encryption concept covered in the lectures. Hint 2: What have you already learned about the key after attempting to decrypt the first message?