The Vigenère cipher is an encryption technique that uses a series of interwoven Caesar ciphers. Although described in 1553 by Giovan Battista Ballaso, it was misattributed in the 19th century to Blaise de Vigenère and ended up being named after him. The cipher is described in detail on Wikipedia at https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher. Only a short summary is presented here.
Although the Vigenère cipher took three centuries to be broken, it is nowadays trivial to break, just as in the case of the Caesar cipher, on which it is based. Like the previous problem, this one is proposed only as a fun and simple exercise and not as an argument in favor of using this cipher for cryptographic purposes.
The technique ...
