Beaufort Cipher
I have been writing about the Vigenère cipher, the first post is here, or you can click on the Vigenère tag. Beaufort is similar, but subtly different.
This post will assume you are familiar with Vigenère.
In the Beaufort cipher, we find the letter in the message on the edge of the grid (e.g. M), then go down to find the letter of the key, X, and finally we read off the encrypted letter, L.
The advantage of this method is that the decryption is exactly the same method - the cipher is reciprocal, so the same code used to encrypt will decrypt.
Beaufort can be broken in exactly the same way as Vigenère, the only real difference is that instead of a Caesar shift, we get a reversed (atbash) caesar shift (MN encrypted with XX gives LK - the letters are reversed, with Vigenère MN encrypted with XX would give JK).
This change requires a few minor code modifications to the code that I’d previously written for Vigenère.
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