PORTA, Giovanni Battista.

A classic of cryptography, and one of the earliest illustrated works entirely devoted to this subject – here with the three volvelles in their uncut state. This is the second edition, an English counterfeit with a false imprint, reprising, in all but the woodcut Habsburg arms on the title, the first Naples edition of 1563. It was published in 1591 by the London printer John Wolfe – trained in Italy and a master of surreptitious imprints, e.g., Machiavelli’s ‘The Prince’; a second issue, with Wolfe’s London imprint and the date 1591, is identical, but for the title. The influence of this ed. on English culture can be seen in Epigram 92 by Ben Jonson: ‘They all get Porta, for the sundry ways / To write in cipher, and the several keys, / To ope the character’.

The Neapolitan Giovan Battista della Porta (1535-1615) published extensively on agriculture, meteorology, natural science and chemistry, and was at the centre of a wide scholarly network including Galileo. Due to his theorisation of magic as an instrument for the understanding of natural phenomenology, he was investigated by the Inquisition in the mid-1580s. ‘De furtivis literarum notis’ (On the Secret Signs of Letters) is a manual of cryptography or steganography, i.e., the art of concealing the meaning of messages from everyone else but the receiver. Among the dozens of ciphers presented and illustrated with woodcuts and tables, there is the first digraphic cipher (Bauer, p.117) and the first modern polyalphabetic substitution cipher, later developed by Vigenère and the WWII Enigma Machine. The work begins by presenting types of secret signs and how to render vowels, semivowels, consonants and mute symbols, with an eye to statistical cryptanalysis, i.e., the most frequent letters are probably vowels, and the use of hieroglyphs. Then it examines ancient cryptography, e.g., the Caesar cipher, and why it was no longer fit for purpose; types of C16 cryptography (e.g., transposition, shifted self-reciprocal substitution) and how to decipher them, with the help of a cipher disk, used for polyalphabetic ciphers. To create the first polyalphabetic substitution cipher, ‘Porta used the idea of a mixed alphabet from Alberti, Trithemius’ square and letter-by-letter alphabet change, and Bellaso’s keyword [‘clavis’] to create a single system for polyalphabetic substitution’ (Dooley, p.39). The work provides dozens of examples showing the original Latin message and its encrypted counterpart, often represented with bespoke woodcut symbols. ‘Porta obviously received excellent assistance from his publisher and printer, for his special symbols did not exist as type and either had to be entered in each copy by hand in writing or with specially made woodcuts. Particularly striking are the pictograms, probably designed by Porta himself, […] and are reminiscent of ancient Egyptian hieroglyphs’ (Zielinski, pp.78-9). Their efforts were matched by Wolfe’s printing workshop. A classic of cryptography in its most bibliographically interesting edition.