Beaufort Cipher
Encrypt and decrypt with the Beaufort cipher — a self-reciprocal polyalphabetic cipher where the same key and operation both encrypts and decrypts.
What Does This Tool Do?
The Beaufort cipher is a polyalphabetic substitution similar to Vigenere but using the formula E = (key − plaintext) mod 26 instead of addition. It is self-reciprocal — the same keyword and operation both encrypts and decrypts.
Key Features
Self-Reciprocal
Same key and click encrypts AND decrypts.
Keyword-Based
Any alphabetic keyword.
Preserves Case
Case of original text maintained.
Copy Result
One-click copy.
How to Use
- Enter your text.
- Enter a keyword.
- Click Encrypt / Decrypt — the same button does both.
Frequently Asked Questions
How does Beaufort differ from Vigenere?▾
Vigenere: E = (plain + key) mod 26. Beaufort: E = (key − plain + 26) mod 26. This makes Beaufort self-reciprocal — decrypting uses the exact same steps.
What does self-reciprocal mean?▾
Applying the same operation twice returns the original text. E.g. encrypt "HELLO" with key "BEAUFORT" → get ciphertext → apply same operation again → get "HELLO" back.
Is Beaufort more secure than Vigenere?▾
They have the same security level — both are broken by Kasiski/index-of-coincidence analysis. Beaufort's advantage is purely operational convenience.