Vigenere Cipher
Encrypt or decrypt with a keyword cipher.
Lxfopv ef rnhr
Vigenere uses a repeating keyword to shift each letter. Stronger than Caesar but breakable with frequency analysis.
About
A keyword shifts each letter by a different amount. Was called 'le chiffre indechiffrable' (the indecipherable cipher) for 300 years until Babbage and Kasiski cracked it in the 1800s. Still good for puzzles and games.
How to use
- Pick encode or decode.
- Type a keyword (letters only).
- Type your text.
- Copy the result.
FAQ
How long should the key be?+
Longer is harder to break. A key as long as the message is mathematically unbreakable (a one-time pad), but only if the key is truly random and used once. Short keys leak patterns.
Is this secure?+
Not against modern attacks. Frequency analysis on the repeated key length cracks it. For real privacy, use AES.