The trick Julius Caesar used to play
Julius Caesar adopted a tricky method of sending messages to his generals through messengers. What if his enemies caught hold of the messenger and read the message? They will then know Caesar’s plans. Caesar’s trick was to change the letters in the message. For instance, he could write “D” instead of “A”, “E” instead of “B” and so on. Every letter would be replaced by another three places further down in the alphabetical order. What do you do with “Y”? What is three places beyond “Y”? The trick is to think of the letters being arranged in a ring so that “A” follows “Z” and “B” follows “A”. In this ring you can go three places from “Y” and find “B”. The letter three places ahead of “Z” will be “C”. To encipher a message, that is to make it secret, we first choose a key. I recommend that you choose a whole number between 1 and 6 as the key. Suppose you choose 3 as the key. Now replace every letter in “TEXT” by one which is 3 steps away along the ring. Do you get “WHAW”? You can send