Cryptography can be a tool that, enables students to consolidate knowledge and develop mathematical skills if used as a recreational or playful activity. In this paper we introduce Caesar’s cryptosystem, which is one of the simplest encryption schemes. It is very easy to crack the encryption of this system: a brute force attack allows easy recovery of the key and the plaintext. We made a simple modification that allows us to have a greater number of keys, in order to make such a brute force attack infeasible. Finally, we show a statistical method that allows us to force this cryptosystem.
