Vigenère Cipher: Encrypt and Decrypt Online Vigenère cipher is a polyalphabetic substitution cipher that uses a keyword to do multiple alphabetic shifts on the plaintext. The encryption of the plaintext is done using the Vigenère square or Vigenère table. Vigenère cipher is a more advanced version of the Caesar cipher that was developed to overcome the frequency analysis attacks. The key is important in determining the number of shifts to be performed across the whole message. The chosen keyword has to be repeated several times until it has the same length as that of the message to be encoded. It was invented by a French mathematician Blaise de Vigenère in the 16th century. You can think of this cipher as a series of Caesar’s shift to make it harder to break. Use the above Vigenère cipher decoder and encoder to encrypt/decrypt simple messages. If this tool was helpful, tweet it or share it.