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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Beaufort Cipher Tool

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Key Text


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  • 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.
  • The Beaufort cipher is reciprocal, that is, decryption and encryption algorithms are the same.
  • A Beaufort cipher works similar to the Vigenère cipher, only that instead of adding letter values, it calculates the cipherletter = keyletter - plaintextletter.
  • 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


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