Do Ciphering in Rome as the Romans Do

Sometimes, ambassadors tend to employ ciphers common at the place they are resident.

I first noticed this in French figure ciphers about the sixteenth century. At the time, most French ciphers employed arbitrary/graphic symbols. The few numerical ciphers tend to be related to Italy. In the case of the Duke of Nevers, some of whose ciphers are numerical (another article), they may well have been derived from his personal Italian connections (the Duke of Nevers was from the Gonzagas). But I cannot see such obvious origins for Paul de Foix, ambassador in Rome, or "Mr de Maisse", ambassador in Venice (another article). The Vatican employed purely numerical ciphers from an early period. (The Venetians introduced numerical ciphers in 1622 Paolo Bonavoglia, "Ottavian Medici and the decline of Venetian cryptography", HistoCrypto 2023, p.22.) It is as if the local courts had initiated the ambassadors with their ciphers, which is improbable for obvious reasons.

I also noticed ciphers with vowel indicators were used by people of several nationalities related to Milan (another article). But the evidence does not yet show any specific relation among those ciphers.

In 2021, I found clearer specimens suggesting Italian influence to French ciphers when I was studying ciphers of Colbert de Croissy (another article). He used ciphers consisting of figures with diacritics in 1659 (DE=28) and 1660 (DE=42~) when he was Intendant of Alsace. But he switched to a purely numerical cipher (1660-1661) during his mission to Rome (DE=91). He used another numerical cipher in Cleves in 1666 (DE=151), but reverted to figures with diacritics (1668-1674) in his London embassy (DE=68), as I pointed out in a blogpost at the time. But I know no evidence that shows Colbert learned numerical ciphers from Italians.

Is it possible that local officials disclose their cipher to foreign ambassadors? It seems out of the question, but I found an episode in which Sir William Temple, an English ambassador at the Hague, studied an enciphered dispatch he could not discuss with John de Witte, the leader of the Dutch Republic.

Temple reported in his letter dated 3 February 1668NS (Temple (1701)) to secretary of state, Arlington that he could not decipher the two letters he received. It seems the cipher employed some new scheme devised by Samuel Morland (as I quoted in another article), but Morland let him practice the cipher only for half an hour, in a rush just before his return to The Hague. Surprisingly, Temple discussed the cipher with De Witt.

... the hazard of my Credit with Monsieur de Witt, who received his Packet while I was with him, and gave me mine that was enclosed in it. When I saw it all in that Cypher, I presently shewed it him, and the conjuring Papers that came with it, and the Key, telling him I doubted I should never cast the Figure right, being so new and unpractised in it. He would not believe I could fail, at least, with Pains, and desired me to go about it, saying, he was impatient to know His Majesty's Answer about inserting the Provisional Articles, which could only be known by this dispatch, since my next would bear date after the arrival of the Treaty in England; and thereupon put me in mind of keeping my Promise with them, which I assured him of. I went home, and after six Hours spent in vain, return'd to him again at Ten that Night, and told him, I came to lose all the Credit I had gain'd with him, by telling him a thing I knew very well he had no reason to believe, which was, That they should send me Letters from Court at this time in a Cypher I was able to make not one word of, and so told him my story; He was a little grave at first, but presently smil'd and told me, I had gain'd greater Credit with him and the rest of the States, than I could lose by a greater matter than this, and said, perhaps he could help me in it, being as much vers'd in Cypher as another Man. I very frankly pulled out my Letter, and my Key, and my Paper with the Rules, and upon it we fell to work together for Two Hours, and all to as much purpose as picking Straws, and so we gave it over, but without the least ill humor, or distrust in him, only saying, Things without remedies must pass, and we must stay till my next Letters came, upon which he would believe I would tell him the King's Answer in that Point, as clearly as if I had seen it now.....

It is desired to study records of ambassadors to find more episodes of this kind of exchange of cryptographic information.

(It is known De Puebla, Spanish ambassador in London, showed his despatch in cipher to Henry VII (another article), but this is too early to be the basis of cryptographic practice in later times.)