Vigenère Cipher
Polyalphabetic substitution cipher using a repeating key.
Input
Output
Using This Tool: Guide & Notes Show guide
The Vigenere cipher uses a repeating keyword to choose a different Caesar shift for each letter position.
How to use it
- Choose Encrypt or Decrypt, then enter the keyword that controls the shifts.
- Paste the message into the input box. Only supported letters are shifted; formatting options control what happens to everything else.
- Use the key stream or status details to check how the repeated keyword lines up with the message.
- Use the same keyword and compatible formatting settings when decrypting.
Options and settings
- Keyword controls the repeating sequence of shifts. Spelling and letter order matter.
- Preserve case keeps the visible case of letters while still applying the same alphabet positions.
- Keep punctuation and numbers leaves unsupported characters in place instead of removing them.
- Group letters creates block-style output for easier visual checking.
Notes
- Short repeated keywords can leave patterns in longer messages.
- Vigenere is stronger than Caesar, but it is still a historical cipher rather than modern security.
Related Article
Vigenère Cipher: When Classical Cryptography Learned to Change Alphabets
How a repeating keyword lets classical cryptography rotate among several alphabets instead of relying on one fixed substitution.