Beaufort cipher decoder and encoder

The Beaufort cipher is named after Sir Francis Beaufort. It is similar to the Vigenère, but the encryption and decryption is reciprocal (the encryption and decryption algorithms are the same). The Beaufort cipher is a polyalphabetic cipher, a series of Caesar ciphers, based on the letters of a keyword.

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Decode Beaufort cipher

Note that you can type in either the ciphertext or plaintext area.

Decryption/encryption settings

Features

  • The Beaufort cipher is a polyalphabetic substitution cipher. The Enigma machine is another example of a (more complex) polyalphabetic substitution cipher.
  • It was named after Sir Francis Beaufort, an Irish officer in the Royal Navy.
  • A Beaufort cipher is equivalent to first applying a Vigenère cipher and then an Atbash cipher.
  • After applying an Atbash cipher, the Beaufort cipher can be broken using same methods as a Vigenère cipher.

Beaufort ciphers, and variants of it, are occasionally used in CTFs, geocaching mystery caches, and logic puzzles.

Sample text

KJHKCOPPQXSKCXTBCV

The ciphertext above represents "SIR FRANCIS BEAUFORT" encrypted using the key CRYPTO.