Coded messages from the ancient Romans

Also for the ancient Romans it was important to use a secret code for their important messages.

The code of Caesar
The Caesar's cipher is one of the oldest code known. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. This number, for Caesar, was 3. We have some evidence of his correspondence with the commander Quintus Tulio Cicero, about military matter.