Giovan Battista Bellaso

Giovan Battista Bellaso was an Italian cryptologist from Brescia, born in 1505 into a patrician family of that city. He took a degree in civil law at the University of Padua in 1538 and later worked in the service of a cardinal, at a time when secret writing was highly admired in the Italian courts, above all in the Roman Curia. His lasting idea was to identify the cipher alphabets by an agreed keyword, a countersign known in advance to both correspondents, instead of signalling each change of alphabet inside the message itself. He also taught ways of mixing the cipher alphabets so that correspondents did not have to exchange disks or prescribed tables. The cipher that grew from this is now called the Vigenère cipher, although Bellaso invented it before Blaise de Vigenère described his own autokey cipher, and it was long considered unbreakable.