A Second Copy of Music Cipher to Charles II Acquired by the British Library (ca.2018)

Sheet music concealed a secret message to Prince Charles (later Charles II) fleeing after the defeat in the Battle of Worcester: "Conceal yourself. Your foes look for you." Another version concealing the same message is said to be for another Prince Charles, Jacobites' Charles III known as the Young Pretender. Both of these have a plausibly sounding story of their provenance. I wrote about these in "Musical Notes Concealing A Warning to Fleeing Prince Charles" back in 2015.
What I didn't know then is that the cipher to Charles II quoted in my article is in the British Library (Add MS 45850, f.68), but its provenance through the Port family I found in googling is about another copy, which the British Library newly acquired (as of February 2018) (Add MS 89288). I learned of this in the British Library's blog article, "'Conceal yourself, your foes look for you': revealing a secret message in a piece of music" (20 February 2018).

I was reminded of this topic when reading Nadine Akkerman and Pete Langman (2024), Spycraft, which refers to Nadine Akkerman (2018), Invisible Agents (the BL's blog also mentions forthcoming publication of this book). Akkerman discusses the nineteenth century copy in BL Add MS 45850 and considers it a hoax. Her dismissal of Jane Lane as the author based on the latter's literacy level is convincing. Even if we assume other authorship, it is hard to think of circumstances in which this kind of cipher came into play ("it is not as if Charles Stuart did not know his enemies were searching for him" etc.).

Use of Diacritics/Exponents/Vowel Indicators in Milanese Ciphers

Some years ago, I noticed the vowel indicator system characteristic of Spanish ciphers in the reign of Philip II had been in use from Charles V's time and similar symbols were also used in Milanese and other ciphers ("Tracing the Origin of Vowel Indicators in Spanish Ciphers").
I now see Milanese ciphers used combined symbols with diacritics or exponents as early as the mid fifteenth century but syllables were not formed systematically as with vowel indicators. I now added a section about this: "Use of Exponents/Diacritics/Vowel Indicators in Milanese Ciphers (1450s-1530s)."
It seems systematic vowel indicators are a degenerated form of such ciphers, but dating of the ciphers in the archives is necessary to assess such a hypothesis.

Constantijn Huygens Jr.'s Secret in Simplistic Concealment Cipher

Constantijn Huygens Jr. (1628-1697), a brother of the physicist Christiaan Huygens, used a cipher in some part of his journals. In late twentieth century, it was found out that encrypted words can be read by simply ignoring odd-numbered letters. For example, b.mregtvelennphnōdesr reads met een hoer ("with a prostitute") (there is one extra letter, which may be an error). The cipher typically concealed such embarrassing privacy of the diarist. I learned of this in Christopher Joby (2014), The Multilingualism of Constantijn Huygens (1596-1687) p.282.

Constantijn Jr. was secretary of Prince of Orange William III (my favoutie historical character) since the latter became stadtholder in 1672. He records his personal experience in participating in major events such as William's campaings to oppose the French invasion, the expedition to England (the Glorious Revolution), and the Irish campaign to prevent the return of James II. Joby (2014) includes some quotes from these (p.284 ff.), and more would be found in Rudolf M. Dekker (2013), Family, Culture and Society in the Diary of Constantijn Huygens Jr, Secretary to Stadholder-King William of Orange. His journals seem interesting in describing historical events from a personal point of view. For example, the day after William III's coronation, from which he was absent, he wrote, "In the early afternoon I was with the king, who asked me where I had watched the coronation. I said that I had been busy deciphering the resolution of the States General, received in cipher, about the alliance with the Emperor, because I thought that the king would want to read this quickly. He asked me if I had received a coronation badge, and I answered no, without receiving much of a response." (ibid. p.40)

Codebreaker Constantijn Huygens

I've heard that Constantijn Huygens Sr. (1596-1687; the father of the famous physicist, Christiaan Huygens) did codebreaking, but it was only recently that I learned that he regularly served in that capacity in Chapter 2 of Nadine Akkerman and Pete Langman (2024), Spycraft (p.153-156). According to this book, he studied cryptanalysis at the University of Leiden in 1616 and even got a pay raise while serving as a secretary to Prince of Orange Frederick Henry since 1624. The authors translate his proud words about his achievements in his autobiography: "At every siege, I proved my skills, anticipating the tricks of the enemy by means of my own knowledge of deceit ...." Particular reference was made to his contribution to the siege of Breda (1637) when requesting a pay raise.

His first achievement in the field appears to have been during Frederick Henry's siege of 's-Hertogenboschin 1629, when he was asked to decipher intercepted Spanish letters in cipher by using his knowledge of Spanish (Christopher Joby (2014), The Multilingualism of Constantijn Huygens (1596-1687), p.78).

He was not always successful. At one time in 1634, he said ciphers of the king of Spain were "more difficult to conquer than" the king himself. (Akkerman and Langman, p.154)

While his library contained many books on cryptography, ciphers he designed for royalists during the English Civil War were simple homophonic substitution ciphers albeit with an extensive nomenclator (ibid. p.156). (I'm inclined to think such ciphers were the most practical after all. John Wallis also proposed a simple Caesar cipher when asked for an "easy cipher", as noted in "John Wallis and Cryptanalysis".)

(By the way, Joby (2014) discusses "code switching", which has nothing to do with cryptography and may be broadly understood as switching to different languages when quoting etc.)

A Second "More Ample" Babington Cipher

Chapter 2 of Nadine Akkerman and Pete Langman (2024), Spycraft details on the undoing of Mary, Queen of Scots, in the Babington Plot and points out many facts which should have been apparent from well-known sources.

(1) The famous cipher used in Mary's fatal letter of 17 July 1586 to Anthony Babington was a very simple one. (The first letter from Mary to Babington dated 25 June 1586 (Pollen (1922) p.15) was also in the same cipher, as I noted in "Ciphers of Mary, Queen of Scots". The 17 July letter was a reply to Babington's response to this first letter.) When one learns that Mary used more elaborate ciphers with other correspondents (as seen in the collection of keys in SP53/22, SP53/23), one cannot help wondering why such a simple cipher was used in this important correspondence.

The authors point out (p.133) that new correspondents were given a simple cipher at first and a fuller one later. Indeed, the 17 July letter ends with "I have commanded a more ample alphabet to be made for you, which herewith you will receive" (cf. Pollen (1922), p.26 ff., esp. p.45).

According to the authors (p.138), such a "mature" cipher was actually used by Babington in his reply dated 3 August 1586 (Pollen (1922) p.46-47, printed from SP53/19 no.10), but the key was intercepted by the authorities and the letter was readily deciphered by Phelippes. Phelippes attests "The new Alphabet sent to be used in time to come between that Queen and Babington ... is of Nau's hande" (I have not checked the cited SP53/19 no.85, which is Phelippes' record of the secretaries' testimony from 4 September, to see whether "in time to come" really refers to the 3 August letter).
[(8/14/2024) Nau's argument is printed in Tytler's History of Scotland. It says "The new alphabet sent to be used in time to come between that Queen and Babington, accompnying the bloody despatch, is of Nau's hand." So the cipher was attached to the 17 July letter (consistent with Mary's wording "herewith") and it may well have been used in the 3 August letter. Curle's cover letter to Barnaby enclosing the 17 July letter says "Giuen hereiwth is the addition to this alphabet" (Pollen (1922) p.25). If this does not refer to an update to the Mary-Babington cipher, such an update may well have been enclosed at the same time.]

(2) Another observation of the authors interesting from a cryptologic viewpoint (p.134-135) is that the well-known copy of the Mary-Babington Cipher in SP12/193/54 is a copy from the original, rather than a product of Phelippes' codebreaking. This can be seen from the nomenclature entries such as "your name" and "myne."

On the other hand, before concurring with the authors' conclusion that Phelippes did not break the Mary-Babington cipher at this time because he already had the key, we may need to assess whether it was feasible to associate a particular intercepted key to Babington (for example, if the three keys on SP12/193/54 were the only keys sent out around June 1586, the authentic key could have been used by Phelippes).

Codebreaker John Somer in the 1580s

An Engilsh Codebreaker, John Somer, was active in the 1560s and the 1570s, as noted in "Ciphers during the Reign of Queen Elizabeth I". On the other hand, the name "John Somer" is often mentioned in 1584-1585 as a secretary to Ralph Sadler, keeper of Mary, Queen of Scots in captivity. I have long wondered whether these are the same person, but now the question is affirmatively answered by Nadine Akkerman and Pete Langman (2024), Spycraft, which induced me to reexamine a little bit. I now added a section "John Somer in the 1580s."

(2024/09/08) I remembered my article on Mary's ciphers mentions Walsingham's forwarding Mary's letter to be deciphered by Somer in October 1582. I now added a mention of this.