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Beaufort Cipher

Reciprocal Vigenère variant cipher for bidirectional encryption and decryption.

Beaufort Cipher

A reciprocal polyalphabetic substitution cipher - the same process encrypts and decrypts

The Beaufort cipher is reciprocal: applying the same operation twice returns the original text. There's no separate encrypt/decrypt mode.

Keyword

The keyword is repeated to match the message length

Options

Preserve spaces and punctuation

Input Text

Characters: 0Letters: 0

Output Text

Example Texts

Click any example to load it

ATTACK AT DAWN

Keyword: FORTIFICATION

Military message

THE QUICK BROWN FOX

Keyword: SECRET

Common phrase

MEET ME AT MIDNIGHT

Keyword: RENDEZVOUS

Secret meeting

How to Use Beaufort Cipher

Enter text and a letters-only keyword.
Keep Preserve Spaces enabled to retain case, spaces, and punctuation.
Read the result generated by the reciprocal Beaufort operation.
Swap the output into the input with the same keyword to recover the original letters.

For each letter, Beaufort computes key minus plaintext modulo 26. The operation is reciprocal, so the same calculation encrypts and decrypts.

Keyword FORTIFICATION — input:

ATTACK AT DAWN

Output:

FVYTGV IJ XTMB

Keyword SECRET — input:

THE QUICK BROWN FOX

Output:

ZXY BKLQU BAQXF ZOU

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