What is a Vigenre cipher?
Vigenre is what cryptologists call a polyalphabetic substitution cipher system, meaning that multiple alphabets are used to encrypt a single message. It was designed in the 16th Century, but then incorrectly attributed in the 19th century to a French cryptographer named Blaise de Vigenre (who had actually designed a different system that was more secure, called autokey). Because of the confusion, the related collection of cipher systems continue to be called “Vigenere” ciphers. For a long time, the system was considered to be unbreakable, but with modern computers, Vigenre ciphers can usually be cracked quite rapidly as long as there is a large enough amount of ciphertext to work from. For more information about Vigenre ciphers, please check here and here.
