The Vigenere Cypher uses the idea that multiple caesar shifts can be used in a repeating pattern to encrypt a text. With the pattern often corresponding to a repeating keyphrase. This French diplomatic cypher elegantly obscures the First Exploit of frequency analasis.

The Cypher utilises the Tablua Recta, shown to the right of the screen. To implement the cypher, you look up the letter corresponding to the collumn letter of the plaintext, and the row letter of the key. Reversing this process to decypher it.

Almost impossible to brute force, as with an unknown key length there are infinite possibilities for the key. However, mathematical analasis can still be used to make an attempt.