Giovan Battista Bellaso

Giovan Battista Bellaso (Brescia 1505–...) was an Italian cryptologist.

Bellaso was born of a distinguished family in 1505. His father was Piervincenzo, a patrician of Brescia, owner since the 15th century of a house in town and a suburban estate in Capriano, in a neighborhood called Fenili Belasi (Bellaso’s barns), including the Holy Trinity chapel. The chaplain was remunerated each year with a regular salary, and a supply of firewood. The family coat of arms was ‘‘On a blue field three red-tongued gold lion heads in side view”.

Bellaso received a degree in civil law at the University of Padua in 1538.

The French author, Blaise de Vigenère, reported that he was serving as a secretary in the suite of Cardinal Rodolfo Pio di Carpi and credited him with the invention of the reciprocal table, now called the Della Porta table. However, Bellaso never mentioned Cardinal Pio in his books and explained that in 1550 he was in the service of Cardinal Duranti in Camerino and had to use secret correspondence in the state affairs while his master was in Rome for a conclave. Versed in research, able in mathematics, Bellaso dealt with secret writing at a time when this art enjoyed great admiration in all the Italian courts, mainly in the Roman Curia. In this golden period of the history of cryptography, he was just one of many secretaries who, out of intellectual passion or for real necessity, experimented with new systems during their daily activities. His cipher marked an epoch and was considered unbreakable for four centuries. As a student of ciphers, he mentioned among his enthusiasts many eminent gentlemen and ‘‘great princes’’. In 1552, he met count Paolo Avogadro, count Gianfrancesco Gambara, and the renowned writer Girolamo Ruscelli, also an expert in secret writing, who urged him to reprint a reciprocal table that he was circulating in loose-leaf form, in print and manuscript. The table was to be duly completed with the instructions. Copies of these tables exist in contemporary private collections in Florence and Rome.

Polyalphabetic substitution with mixed alphabets, frequently changed without a period, is attributed to Leon Battista Alberti, who described it in his famous treatise De cifris of 1466. This crucial invention has a limit in that it obliges the encipherer to indicate, within the body of the cryptogram, the index letters determining the choice of the next alphabet. It was Giovan Battista Bellaso who first suggested identifying the alphabets by means of an agreed-upon countersign or keyword off-line. He also taught various ways of mixing the cipher alphabets in order to free the correspondents from the need to exchange disks or prescribed tables.

...
Wikipedia