Vigenère cipher
Encrypt or decrypt a text with the Vigenère cipher, a classic polyalphabetic substitution method based on a text key.
How it works
The Vigenère cipher shifts each letter of the text according to the corresponding letter of a key repeated over the entire length of the message, which makes the encryption more resistant than a simple Caesar shift. Useful for practicing classic cryptography or disguising a message for fun — this is not secure encryption for modern sensitive data.
What happens to digits, spaces, or punctuation?
Only letters (a-z, A-Z) are encrypted or decrypted; digits, spaces, and punctuation marks remain unchanged and don't advance the position in the key.
Does the key need to be the same length as the text?
No, the key is automatically repeated as many times as necessary to cover the entire length of the text being encrypted.
Encryption runs entirely in your browser via WebAssembly, your text and key never leave your device.