Type your text and a keyword, and the tool encrypts or decrypts it using the Vigenère polyalphabetic cipher.
A series of Caesar ciphers with different shifts determined by the letters of a repeating keyword.
Much stronger than Caesar but still breakable via Kasiski examination for long ciphertexts. Not suitable for modern security.
A single word or phrase using only letters (A—Z). Longer keys are harder to crack.