Full Decipherment of Pedro de Ayala's Letter to Ferdinand and Isabella (1498)

Three historians have achieved complete transcription and decipherment (as well as full translation into English) of a partially enciphered letter from Pedro de Ayala to Ferdinand and Isabella dated 25 July 1498. (I thank George Lasry for bringing a report in French by Korben to my attention. Its source is Medievalists.net in English.)
The paper was published on 16 March 2026:
Adrian William Jaime, Valeria Tapia Cruz, Mairi Cowan (2026), "Tudor England and Stewart Scotland Through Spanish Eyes: A Complete Transcription and Translation of Pedro de Ayala's Letter of 1498 to King Ferdinand of Castile and Queen Isabella of Aragon", DOI: https://doi.org/10.1111/rest.70019 (an online version before inclusion in an issue of Journal of the Society for Renaissance Studies).
The original letter in the archives (PTR,LEG,52,166 f.857) is available at PARES.

The letter itself has been known to historians by a calendar by Bergenroth (Google, p.168) and also by Almazán's summary "currently archived together with the original manuscript". (Quotations are from the paper. See several paragraphs from n.74.)
Bergenroth deciphered passages in cipher and his key is in PRO31/11/11 in three versions ("Correspondence with Pedro de Ayala and Don Martin", "Cifra de Don Pedro de Ayala", "1498 Pedro de Ayala"; see "Bergenroth's Papers on Spanish Ciphers in PRO 31/11/11"). However, it has been pointed out that "his edition contains mistakes, and much of the English version printed in the Calendar of State Papers is more a paraphrase than a direct translation" and there have been works for a more accurate edition for parts of the letter. The authors' key "builds off the work of Luis A. Robles Macías ["Transcripción revisada del informe de Pedro de Ayala de 1498"], adding new symbols based upon how Almazán deciphers the letter in his summary." 

 

Extending the Key of Barbeu-Dubourg's Passage Cipher with Franklin

Barbeu-Dubourg is known for translating Benjamin Franklin's work into French.

In his letter written from 10 June to 2 July 1776, he sent Franklin a cipher. It was a passage cipher whereby each letter of a key text is assigned sequential numbers. A similar scheme had been used between Franklin and Charles William Frederick Dumas.

The letter is in PCC (Papers of Continental Congress), (roll number?) p.70 and printed in Papers of Benjamin Franklin, vol.22, p.453-470.

The short specimen allows partial reconstruction of the original key text.

Such Barbeu-Dubourg's passage cipher is described in Weber (1979), United States Diplomatic Codes and Ciphers 1775-1938 and my article, "Benjamin Franklin's Codes and Ciphers" (2009). Actually, more is known from:

Leighton, A.C., Matyas, S.M. (1985). The History of Book Ciphers. In: Blakley, G.R., Chaum, D. (eds) Advances in Cryptology. CRYPTO 1984. Lecture Notes in Computer Science, vol 196. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-39568-7_11 p.105.

The example given by Barbeu-Dubourg is:

3,2,Β,19,5,23,16,12,γι,44,53,δ,10,51,4,61,θ,36,17,6,24,71,1,λ,42,28,37,33,μ,82,54,11,9,8,47,59,88,13,69,ξι,31,92,π,72,34,56,73,σ,6,94,4,20,φ,40,100,68,48,ψω

(The Greek letters are word breaks.)

The latter half of the example is left without decipherment. This kind of cipher cannot be deciphered without finding out the key text, but Leighton succeeded in extending the key text with the assistance of Dr. Eric Gans, who thought of extending the plaintext "Ma femme et deux filles vous" with "embrassent de tout leur etre".

3 2 * 19 5 23 16 12 * 44 53 * 10 51 4 61 * 36 17 6 24 71 1 * 42 28 37 33 * 
m a    f e  m  m  e    e  t    d  e u  x    f  i l  l  e s    v  o  u  s   

82 54 11 9 8 47 59 88 13 69 * 31 92 * 72 34 56 73 * 6 94 4 20 * 40 100 68 48
 e  m  b r a  s  s  a  n  t    d  e    t  o  u  t   l  e u  r    e   t  r  e

It is remarkable that there are few repetitions. The mere two instances of consistent assignment 4=u and 6=l are hardly enough to justify the extension. But when these figures are sorted, a meaningful key text emerges.

(In the above image, highlighted cells are from the extension.)

It will be reasonable to read the beginning (SAMUEL_ARDBEN__MI_FR__ML__) as "Samuel Ward Benjamin Franklin" (M toward the last is an error for K). (Samuel Ward was a member of the Secret Committee of the Continental Congress (Rhode Island Historical Society, One Eternal Day (by Standfast)), of which Franklin was among the original members.)

The occurrence of these names hardly seem to be a coincidence and thus makes the extension plausible (at least for the part involved in these names).

It will be seen there are higher numbers yet unaccounted for. If someone can think of some plausible text to fill the gaps, I'd like to know, though it will be more difficult because known figures are sparse.

The following revisits Leighton's extension. Absence of highlight for "de tout" and "etre" indicates these may be altered without affecting the above discovery.

A British Book Cipher during the American Revolutionary War

During the American Revolutionary war, a book cipher was used between Frederick Haldimand, Governor in Quebec, and Sir Henry Clinton, Commander-in-Chief in New York. It is described in a new article, "Haldimand-Clinton Book Cipher (1778-1782)".

It appears that the book cipher was also applied in letters from Lord Germain. It is wondered whether ciphers had not been used in trans-Atlantic communication. British ciphers during the Revolutionary War are also outlined.

An Essay on Spanish Ciphers by 19th Century Archivist at Simancas

AGS (Archivo General de Simancas) Est. Leg. 1.1.1 is a collection of 238 ciphers from various times. Regrettably, these ciphers are not organized or properly labelled, as I hear.

The other day, I learned in Pich-Ponce (2024) (see here for citation) that Claudio Pérez y Gredilla compiled ciphers in AGS in "El Libro de cifras" (AGS D/203). According to Otto Vervaart's blog, it is an unpublished manuscript and deals with about 200 ciphers. (I guess AGS Est. Leg. 1.1.1 is its major scope.)

Perhaps Benavent (2025) refers to the same manuscript by "El estudio de la claves" written by Claudio Pérez y Gredilla, an official of the archives. She tells this essay was even favourably reviewed for publication by Antonio Rodríguez Villa in Boletín de la Real Academia de la Historia.

A list of Rodriguez Villa's papers at Biblioteca Virtual includes the review:

Rodríguez Villa, "Cifra diplomática", Boletín de la Real Academia de la Historia, tomo 24 (1894), p.108-109 (bibliography, text). (It shows that Claudio Pérez y Gredilla was head of AGS and the title given by Benavent is correct.)

Benavent says it is not certain whether Claudio Pérez y Gredilla's essay was ever printed. Given that it is at least not easily accessible now, I hope someone publishes its edition somewhere. (For example, Cryptologia accepts "From the Archives" pieces.)

Two More Ciphers of Emperor Charles V in 1527 Identified

When I called for a match for unsolved Charles V's ciphers in a collection of ciphers from 1521-1527, George Lasry immediately responded with solutions produced by his solver. I now added a section for these in an article for his achievements. As it turned out, I already posted his solution to one back in 2023 but I was not aware of it in writing the last blogpost. (The solutions still require attention of someone versed in Spanish.)

This adds two more ciphers to the collection of Charles V's ciphers from 1521-1527 in Kolosova (2017) I introduced here.

It is interesting that the Marquis of Gasto (Guasto, Vasto) used different ciphers in writing to the Emperor in September and November 1527.

Can You Find a Match from a List of Ciphers of Charles V?

Three ciphers used in letters to/from Charles V remain unsolved ("Unsolved Historical Ciphers"):

- Letter from Emperor Charles V (1521?): BnF Clair. 322, f.105v (Gallica)

- A Report to Charles V (1527?): BnF fr.3022, f.16 (Gallica)

- Marquis of Gasto to Charles V (1527). ff.26-28, 39, 40-43 (Gallica)

When I came to know 17 ciphers reconstructed by Olga Kolosova from letters to Charles V in 1521-1527 ("Scholarly Studies on Ciphers in the Reign of Emperor Charles V"), I was thrilled because the scope exactly matched these unsolved ciphers. But I couldn't find a mathing cipher among her reconstructions. It may well have been that the three ciphers are simply not among the 17 reconstructions, but I have to admit my search was not thorough. I simply looked for a couple of symbols in each cipher (e.g., "3" with an additional stroke below in BnF fr.3022, f.16; "s", "3", "v" with two additional lines in BnF fr.3022, f.26). Although this worked for Mary-Grange Cipher (1571) (see here), there's some chance that I simply overlooked this time. If someone finds a match, please let me know.

NB. BnF fr.3022 also includes other ciphers:
f.12 (no.5) Perez to Charles V, Rome, 24 September 1527 (the same cipher as in BnF Clair.326): George Lasry solved this. I also found it matched a cipher I reconstructed. The cipher corresponds to one of Kolosova's reconstructions (Ko.1).
f.16-f.17 (no.6) Report to Charles V, unsolved (see above).
f.20 (loose sheet) The same cipher as f.12.
f.26-28 (no.10) Marquese del Gasto to Charles V, Ysola, 27 September 1527, unsolved (see above).
f.39 Belong to the following?
f.40 Marquese del Gasto to Charles V, Rome, 6 November 1527, unsolved (see above).
f.44 Memoire in Italian, Madrid, 11 April 1528, unsolved (see here). The symbols with superscript figures look like those in Lu.6 (used by Andrea Doria and Charles V in 1537) reconstructed by Luo (2021) but the range of figures does not match at all.
f.48 Jargon in Italian (ibid.)
f.50 "Aditione del zifra" (ibid.)

Recent Studies on Ciphers in the Reign of Emperor Charles V

When working on some recent posts, I noticed there has been active research about ciphers in the time of Emperor Charles V in the past few years. I outlined them in a new article, "Scholarly Studies on Ciphers in the Reign of Emperor Charles V" with some observations from cryptographer's perspective.

Most of the many ciphers reconstructed by scholars from archival materials are not covered in my article, "Ciphers during the Reign of Emperor Charles V", while my article also has some not covered by their work. In a few cases where we work on the same cipher, independent reconstructions will supplement each other.