[CRYPTOGRAPHY].

C16 MS. CRYPTOGRAPHIC ‘NOMENCLATORS’ FOR AMBASSADORS

Two ms. cryptographic ‘nomenclators’, one produced for the French ambassador in England.

France, probably Flanders, Manuscripts, on paper, I: c.1561; II: 1576-95

£5,750.00

Brown ink, secretary hand, in French. I: 330 x 218mm, ff. [2], [*]2, 1 page of text (11 lines), docket to second verso, watermark: hand, edges untrimmed, very minor toning, folds minimally dust-soiled to second verso, one light ink spot to text; II: 350 x 232mm, ff. [2], [*]2, 2 pages of text (triple column, c.50 lines per full page), watermark: column and ‘Claude Denise’ at foot (cf. Briquet 4435, c.1588), edges untrimmed, just toned, small light water stain to central fold towards gutter, second blank verso a trifle dust-soiled. Unbound. Contemporary ms. inscription ‘Chiffre de Monseignur’ to second verso of II.

Two C16 ms. cryptographic ‘nomenclators’ – in very fine condition – i.e., ‘keys’ to official encoded documents, one produced for the French ambassador in England c.1560. They are rare relics of the crucial link between the growth of diplomacy and the development of ever-complex cryptographic theories, in the C16. By the end of the century, ‘cryptology had become important enough for most states to keep full-time cipher secretaries occupied in making up new keys, enciphering and deciphering messages, and solving intercepted dispatches’ (Kahn, pp.108-9). 

A nomenclator is ‘a system of encryption that relies on a cipher alphabet, […] used to encrypt […] a message, and [on] a limited list of codewords’, which work by substitution; in codewords, ‘each word is represented by another word or symbol’ (Singh, pp.29, 27). These mss are both instances of ciphers based on monoalphabetic substitution; they also employ techniques devised to prevent deciphering by means of frequency analysis (whereby the most frequently used letters/numbers in a message stand for the most common letters in the alphabet). Both mss also include instances of homophonic substitution ciphers, whereby, as ‘each letter is replaced with a variety of substitutes’, the number of potential substitutes remains proportional to the frequency of the letter (Singh, p.54). The technique remains in use.

 The first ‘nomenclator’ is a ‘Chiffre po[ur] Mons[ieu]r de la Forest avecq[ue] Mons[ieu]r de Foix Ambassadeur en Angle[ter]re’, dated ‘1561 Flandres’. Late in 1561, Paul de Foix (1528-84) was appointed French ambassador in England. He quickly paid his homage to Mary Queen of Scots, who had only recently returned to Scotland from France. He was succeeded by Jacques Bochetel de la Forêt in 1566. The contemporary secretary hand is almost identical to that on a French nomenclator of 1554, in the Florentine Archivio. The very common hand watermark decreased in frequency in France in the third quarter of the C16 (cf. Briquet). This nomenclator also features ‘nulls’, i.e., words, letters or symbols which represent nothing, and were solely used to confuse frequency analysis. Equally, double letters and common monosyllables are rendered with one symbol, whilst single letters, occasionally, by two.

 The second nomenclator features a very long list – 256 lines of ciphers or codes – of homophonic substitutions of letters and words. Part I lists combinations for the 25 alphabet letters, according to their frequency, using numbers to represent monosyllables. Part II lists the names of kings, princes, aristocrats, ambassadors and countries, as well as national adjectives, all rendered by one or more numbers. A note states that nulls or + may be added to muddle decryption. The frequency of names can help identify an approximate time of production. The presence of Archduke Ernest of Austria suggests that the ms. was produced in 1576-95; the Spanish ambassadors J.B. de Taxis and Don Diego de Ibarra were especially active in the early 1590s. The high number of substitution ciphers for Taxis, Ibarra, the Duke of Parma, Monsieurs de la Châtre (French ambassador in England) and Duplessis-Mornay, points to the years of the French Wars of Religion (c.1589-92).

S. Singh, The Science of Secrecy (2000); D. Kahn, The Codebreakers (1966); Florence, Archivio di Stato, Cifrari della Repubblica e medicei, No. 457.