Vigenère Cipher — Free Online Tool
The Vigenère cipher uses a keyword to apply different Caesar shifts to each letter. Each letter in the key sets the shift for the corresponding plaintext letter. Much harder to crack than a single Caesar shift.
100% client-side. No uploads. Your data never leaves your browser.
How to use Vigenère Cipher
- Enter your message.
- Enter a keyword (letters only).
- Choose Encrypt or Decrypt.
- Click Apply.
Frequently Asked Questions
How do I choose a key?
The key should be a word or phrase using only letters. Longer, random-looking keys are harder to break. The key repeats to match the length of your message.
Is Vigenère cipher secure?
It was considered unbreakable for centuries but was solved in the 1800s using the Kasiski examination. Not secure by modern standards — use it for fun and history.
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