Vigenère Cipher Encoder / Decoder
Encrypt or decrypt text with a keyword using the Vigenère cipher.
Ciphertext
About the Vigenère cipher
The Vigenère cipher is a polyalphabetic substitution cipher: instead of a single fixed shift, it repeats a keyword across the message and shifts each letter by the position of the matching key letter. With the key LEMON, ATTACKATDAWN encrypts to LXFOPVEFRNHR. For centuries it resisted casual code-breaking, earning the nickname le chiffre indéchiffrable. Only letters are enciphered — spaces, digits, and punctuation pass through, and the key only advances on letters.
For the simpler single-shift version, see the Caesar cipher or ROT13. All enciphering happens locally in your browser.
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