For three centuries people thought the Vigenere cipher was unbreakable, and it outlived every plain Caesar by a comfortable margin. A keyword shifts each letter by a different amount, so the pattern that betrays simple shifts disappears.
Encrypt and decrypt with a keyword, A-Z only, and the tool handles the shifting both ways. Use it to understand the old technique, to send messages your friends can decode with a shared word, and to appreciate how codebreaking got to where it is.
Try it now: open the free tool, runs 100{ddff9936f8333f09603555df7bd6492034f3a4a35de784276d3cf3d66166a113} in your browser.
Bottom line: same keyword to encrypt and decrypt, capitals and spaces matter.
Your turn: use the tool free here, no signup, nothing leaves your device.
How do you use Vigenere Cipher?
Open the Vigenere Cipher in your browser (Keyword-based cipher). Type or paste your input, adjust the options, and copy the result. Everything runs locally on your device with no account and nothing stored, so the three steps below take seconds even for confidential work.
- Paste the text you want to work with.
- Choose the transformation you need.
- Copy the result, or tweak the input to see it update live.
Try Vigenere Cipher free. It opens right in your browser.