Julius Caesar used cryptography during the Gallic Wars.

His method was to substitute each letter in the alphabet by that letter shifted right by some fixed offset.

For example, if the offset is 3, then the replacements are

A->D, B->E, C->F, ... , W->Z, X->A, Y->B.

In what follows, if you enter a message in the text area and press Encrypt, the computer chooses a random offset and you see the resulting scrambled message. Then ask a friend to try to unscramble it. You can press Decrypt to see the original message.

Enter plain text to be encrypted below: