Blaise de Vigneré publishes the Vigneré Cypher. It uses 26 different encryption alphabets, each shifted by one letter from the previous one, making the system impervious to letter-frequency analysis, the weakness of previous codes. His work culminates in his Traicté de Chiffres of 1586. Ironically, this is the same year that Thomas Phelippes cracks the secret code of Mary Queen of Scots’ letters. If Mary had read the treatise and used the Vigneré Cypher, Phelippes would not have been able to crack her code, and Mary would not have been beheaded. In any case, the Vigneré Cypher would remain virtually unknown for another two centuries. This encryption technique had been pioneered by Leon Battista Alberti, but he never fully developed it. This is, in fact, the first significant advance in encryption for over a thousand years, in which decryption has always had the edge.
