What is Vigenere cipher?

It is a technique for encrypting messages consisting of only text and no special characters or numeric digits. It is derived from a much simpler and one of the oldest known encryption systems called Caesar cipher. In the Caeser cipher, the encrypted text is obtained by replacing each character of the original text by a character away from it by a fixed number of places in the standard alphabet. For example, if the displacement is decided as 1, then the original text ‘open space’ according to the above technique gets encrypted as ‘pqfo tqbdf ’. In the Vigenere cipher, unlike in Ceasar cipher, the displacement involved for each character is different. The sequence of displacement is decided by a keyword, which is known to both the encryptor and decryptor beforehand. The technique was said to have been discovered by Giovan Battista Bellaso in 1553, but was wrongly attributed to Blaise de Vigenere.