Giambattista Della Porta’s fame (Napoli 1535 -1615) is linked to the extraordinary best-seller De Magia Naturalis (1558) and the life-long studies in multiple fields, mainly verifying the magic traditions as natural but “wonderful”’ practices, freeing them from superstition or demonism. Despite his theories and writings brought him very close to heresy his intent was to make magic fully legitimate and acceptable as natural knowledge, widely usable with much less religious and moral concern than in the past.
The young Neapolitan prodigy and future founder of the first scientific society of the Renaissance explores and excels in several other field. He was twenty-eight years old when he wrote the book to which he owes his fame as a cryptologist. The De Furtivis Literarum Notis (1563) consists of four books dealing respectively with ancient ciphers, modern ciphers, cryptanalysis and linguistic characteristics favoring deciphering. It represents the sum of the cryptographic knowledge of the time. He summarizes the classic procedures of his predecessors, not hesitating to criticize them.
Porta classified the processes into three categories: the change in the order of the letters (transposition), their shape (substitution by symbols), their value (substitution by cryptographic alphabet). He was the inventor of the first double-key literal system, the first cipher for which the alphabet is changed at each letter.
Bibliografy: Kahn David, La guerre des codes secrets, InterEditions, 1980, pp. 35-37 ; Adams P-1924; BL/STC Italian Books p.536; Caillet 8850; Mortimer/Harvard Italian 397; Riccardi I(ii), 309: ‘bella e rara edizione’
