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 "leur" 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.

A Code of Count of Maurepas, Secretary of State of the Navy (1733)

I uploaded "A Code of Count of Maurepas, Secretary of State of the Navy (1733)", which is based on letters and reconstruction provided by Alexandre Pillon. He is a collector of ciphers and has kindly provided me with a lot of materials about ciphers of Louis XIV, delegates for peace negotiations, Torcy/Gualterio, and Georg Adam Starhemberg. 

 

A Power from Prince Philip Arrived in Cipher (1554)

Simon Renard mentioned yesterday was a familiar figure to me as the "bad guy" in Jane Grey's story I read as a child (Ainsworth's The Tower of London adapted for junior readers) or in a 1986 film "Lady Jane".

I mentioned some episodes related to him from CSP in "Ciphers during the Reign of Emperor Charles V". At one time, Renard was puzzled because he received a power from Prince Philip but it was in cipher.

While writing these letters I received a packet from his Highness dated November 12th. The courier was delayed 40 days at the port of Plaisance. I have no news of the other three who passed this way. His Highness's letters confer upon me full power to promise whatever is necessary for the marriage, but as they are in cipher, I do not see how I can use them. I will inform the Queen, however, the better to confirm her in her resolve.
(Renard to Charles V, 18 January 1554) (CSP Spain)

The Spanish ambassadors in England had been negotiating for the marriage with authorities from the Emperor, but the English required a power signed by Prince Philip himself because they wanted to be assured that the Prince would not repudiate the agreement to restrict his power in England.

I suppose the problem here was not about cryptography but that the original power in clear (rather than decipherment) should be presented to the English government.

Soon after this, the Emperor in Brussels signed the agreement and required the Prince in Spain to ratify it and return it with powers for the contraction of the marriage (CSP Spain).

Three Ciphers Used in Correspondence between Granvelle and Simon Renard

Antoine Perrenot de Granvelle, a trusted secretary of state of Emperor Charles V, and Simon Renard, ambassador to England, used three ciphers, according to Eva Pich-Ponce (2023a), "Les messages secrets d'Antoine Perrenot de Granvelle à Simon Renard : la question du mariage de Marie Tudor", Thélème 38(2) (DOI: https://doi.org/10.5209/thel.90555 ), a study of volumes of "Collection Granvelle" in the Besançon Municipal Library (esp. ms. 73). (Their letters per se are familiar to historians (e.g., CSP Spain). They are in French because both were from Burgundian families.)

The first cipher is the one used by Jean de Saint-Mauris as early as 1544, reported separately in Eva Pich-Ponce (2023b), "La cifra secreta de Carlos V y la subida al trono de María Tudor", C&eacyte;dille (DOI: ttps://doi.org/10.25145/j.cedille.2023.24.22 ). This particular cipher attracted attention by a discovery by Pierrot, Gaudry, Zimmermann, and Desenclos in 2022 and had also been reported in my article, "Ciphers during the Reign of Emperor Charles V".

It was used in more than 100 letters until 1554 by the Emperor, Saint Mauris, Simon Renard, the Bishop of Arras (Granvelle), Mary of Austria, the Bishop of Luxeuil, Francisco de los Cobos, and Ferdinand (brother of the Emperor). In particular, the Emperor used this in 1553 in his letters to ambassadors in England about the succession (Jane Grey, "Nine Days Queen", was on the throne in July 1553) and the marriage of Mary Tudor with his son Philip. Between Granvelle and Renard, this cipher was used from December 1553 to May 1554.

The second cipher was only used between Granvelle and Renard, in contrast with the wide usage of the first cipher. It was used in Granvelle's five letters from August to November 1553. This cipher is the focus of Pich-Ponce (2023a).

The third cipher was used from 1549 to 1554 by the Emperor, Mary of Austria, Nicolas Perrenot and Antoine Perrenot, and Renard (with a less wide distribution than the first cipher).

The second cipher is much simpler than the first. In particular, it lacks syllables as found in the first cipher. Moreover, the second cipher was only used sparingly. The longest passage in this cipher I spotted is "s-o-n i-n-c-l-i-n-a-c-i-o-n e-t c-o-n-t-e-n-t-e-m-e-n-t" (f.40). This is in contrast to the first cipher, wihch was used to encipher the substantial portion of the whole letters, apparently by a professional secretary. The third cipher (to be treated in Pich-Ponce's coming paper) seems to be closer to the first cipher both in structure and use.

Why did this second cipher have to be introduced, when the first and third ciphers were already available? It was not that the latter ciphers were obsolete or compromised, given that they continued in use after the span of the second cipher. Pich-Ponce considers it was because of the Emperor's desire for strict secrecy, without even letting his closest circle know the content (p.116-117). Her explanation of the historical situation (the Emperor had to be sure of Mary Tudor's inclination before formally broaching the subject of her marriage to Philip) is very interesting. But given the weak nature of the second cipher (both in structure and use), there might have been other factors. (I'd like to know in what situation the Emperor (or Mary of Austria on his behalf) directly wrote to Renard (by a secretary) and in what situation Granvelle wrote to him (personally?).)

The vocabulary of the nomenclature seems to indicate the cipher was prepared for the issue of Mary Tudor's marriage. 40 (étranger) and 45 (mariage) are used to express "mariage étranger" (foreign marriage), as opposed to marrying an Enlishman (such as Edward Courtenay, a great-grandson of Edward IV).

Her study revealed 1553 was a year when the lifespans of the three ciphers overlap. I look forward to her coming paper about the third cipher.

A Cipher Used by Margaret of Austria (1508) (Not Properly Scanned)

Speaking of Mary of Austria, the Governor of the Netherlands before her, Margaret of Austria, also used ciphers. I mentioned a very simple one in "Ciphers during the Reign of Emperor Charles V". Correspondence de Marguerite d'Autriche (Google) also records use of cipher in her correspondence. It has an appendix of cipher, but regrettably the fold-out is not properly scanned (in all the copies I found).

It should include:

N^o. I. Chiffre latin de l'empereur Maximilien et d'André de Burgo. V. les lettres N^o. 45 et 49.
N^o. II. Chiffre français de Jean de Courteville. V. les lettres N^o. 2, 10, 15, 16, 18.
N^o. III. Chiffre gueldrois de Jean van der Horst. V. la lettre N^o. 155.
N^o. IV. La lettre N^o. 155.

The cipher no. I should be the one used in the letter from Emperor Maximilian to Margaret dated 23 July 1508 (N^o. 49).

The transcription of IV allows reconstruction of the cipher III used by Jean van der Horst (who is considered to be an "officier" of Charles, Duke of Guelders.)

 

A Cipher Used by Mary of Austria (1546)

I mentioned ciphers used by Mary of Austria, Governor of the Netherlands and sister of Emperor Charles V, in "Ciphers during the Reign of Emperor Charles V" but have not seen an actual specimen. A cipher used in two letters from her to [Nicolas Perrenot de] Granvelle in 1546 is reconstructed in Francisco Javier Reales Pérez (2025), "Déchiffrer l'histoire : présentation et description d'un chiffre employé par Marie de Hongrie dans sa correspondance en langue française", Estudios Románicos, vol. 34, pp.159-177 (DOI: https://doi.org/10.6018/ER.614131 ).

The cipher has a homophonic substitution alphabet, symbols for double letters, nulls, syllables, and words. Syllables such as ba, be, bi, bo, bu are generally represented by some base symbol plus an indicator to distinguish the vowels. However, unlike the regular vowel indicators in Spanish ciphers under Philip II, the indicators are not regular. This is a characteristic (better than in the next reign!) also seen in other Spanish ciphers during the reign of Charles V (see my article quoted above).

An Undeciphered Letter from Henrietta Maria (1648)?

It appears odd pieces of letters related to Charles I are preserved in many local arcihves in Britain (I reported one such case some years ago.)

Sixth Report of the Historical Manuscripts Commissions (1877) has a section "Second Report of the Manuscripts of His Grace the Duke of Argyll, K.T. By William Fraser, Edinburgh" (p.606 ff.), in which no.25 may be an undeciphered letter of Queen Henrietta Maria to a recipient written in cipher (p.612). The record reads:

no.25 Henrietta Maria, Queen of Charles the First: Addressed in ciphers thus : 109. q. O : 303. 13. 502.
St. Germain, 22 January 1648. This letter is written chiefly in ciphers, and subscribed "votre affectionne cousine et amie. / Henriette Mame E."

This is a period during which no letters are known in the collection of her letters (Internet Archive).

I wonder where the letter is now archived. I think it's somewhere around Campbell faimly, Dukes of Argyll, Papers, but I could not locate it in the catalogue. If someone finds its current location (or better still, solve it), please let me know.

An Imperial Diplomat Resists Updating Ciphers (1646)

An episode of an Imperial resident in Constantinople, Alexander von Greiffenklau zu Vollrads (1643-1648), who resisted updating ciphers, is mentioned in a paper in German,

Würflinger, C. (2020), "Die Verschlüsselung der Korrespondenz des kaiserlichen Residenten in Konstantinopel, Alexander von Greiffenklau zu Vollrads (1643-48)", Chronica. Annual of the Institute of History, University of Szeged, 2020(19), 6-23. https://ojs.bibl.u-szeged.hu/index.php/chronica/article/view/34020

From the first, his reports enciphered only small portions of his letter. In one instance (27 September 1643), only numbers coressponding to the alphabet were used, without using numbers for whole words. (p.18-19)

In a letter of 22 September 1646, he appears to resist updating the cipher. While saying he would be happy to use the new cipher and would accommodate himself when necessary, he explains that the updating would cause him "irreparable confusion and hindrance" because, in view of the available transport means, the time would not allow him and his copyist to use ciphers other than those they were accustomed to. He warns the home ministry that otherwise he would need to write in clear or omit sensitive matters. (p.13-14, n.46; "ablehnte" on p.15).

The new cipher provided for homophones, while the alphabet of the old one was monoalphabetic (Table 1, 2). Code words were changed (p.15). (In the end, Greiffenklau appears to have used the new cipher, because Table 3, apparently belonging to the new cipher, shows code words used in his correspondence. But I'm not sure of this partly because I rely on machine translation.)

The key ("die Schlüssel") is in the archives (n.53, catalogue page).

Greiffenklau is mentioned in Birkner (2015) quoted in the paper (and also by me), but his cipher is not among the eight discussed therein. Birkner (p.178) gives an example encipherment in the cipher (1643) of Greiffenklau's predecessor, Johann Rudolf Schmidt, Baron von Schwarzenhorn, which (in my interpretation) is: 64(Ko)22(n)27(s)166(ta)22(n)168(ti)104(no)127(pe)20(l) 157(se)17(h)107(en) 68(lie)142(be)22(n) 258(und) 27(S)167(te)26(r)137(be)22(n). The same cipher was given to Hermann Graf Czernin von und zu Chudenitz in 1645.

I believe Greiffenklau's cipher also included numbers for syllables like this.

French Ciphers for German Affairs

Two reconstructed ciphers for ambassadors to the Emperor are presented in a new article, "French Ciphers for German (and Eastern) Affairs".
There is also another cipher used in letters to the King of Poland, who was soon to return to France be crowned as Henry III. This turned out to be the cipher used by an ambassador to Constantinople I reconstructed before!

French Numerical Ciphers from the 1570s

I uploaded a new article "French Numerical Ciphers from the 1570s". My first plan was just to present two reconstructed ciphers but the result is more focused on a brief overview of French numerical ciphers, collecting what I have mentioned in various places.

Reconstruction of a Cipher used by Charles de Danzay, French Ambassador to Denmark

A letter from Danzay, French ambassador to Denmark, to Henry III (1574) includes a undeciphered paragraph, which has been on my list of unsolved ciphers here. It may have been too short to solve analytically, but Sergey Ryabov succeeded in reconstructing the cipher by finding another letter (1578) with decipherment in the margin. Now I updated the record.

To me, Danzay is interesting because of his unparallelled long tenure from 1548 to 1589. Comparison of ciphers used during his career may shed light on practices of French cryptography at the time. For the time, I found one from 1557.

I uploaded a new article "Danzay's Ciphers: Ciphers of a French Diplomat with a Long Tenure" to report Danzay's ciphers from 1574-1578 and 1557.

Vigenere's Cipher That Allows Two Readings

I uploaded a new article, "Vigenere's Chiffres à Double Entente", which allows two readings of a ciphertext.

I have been interested in such a cipher that allows disclosing one of the two plaintexts but not the other and I was aware that Vigenere deals with "chiffre a double sens" as of my blog post in 2021.

Now I've studied the relevant pages in Vigenere's work.

In my understanding, Vigenere's chiffre à double entente or double sens works in a manner similar to a running key cipher, in which a first plaintext is combined with a second plaintext instead of a key text. Since the key text is not given for deciphering, each cell of the square table provides two letters instead of one. So, seen end-to-end, it is effectively a digraphic cipher.

Although the scheme may not provide effective protection against pressure from a tyrannical government, I find it interesting enough to be used in a detective story or film.

Factor Exponent Cipher (from TV Series "Hard Nuts")

A simple cipher used in a Japanese TV series is described in a new article in Japanese 「ハードナッツ」の暗号（素因数分解指数暗号）. It is basically simple substitution, but involves an additional layer of factorization/exponentiation. Try to decipher the following:

110487239481514742664955700062500000.

The key is written below in white, which you can see by selecting.

Factor the ciphertext:

110487239481514742664955700062500000=2^5*3^14*5^9*7^7*11^13*13^1

(It was interesting to see that AI failed in this simple task.)

The exponents represent letters in the alphabet:

5(E) 14(N) 9(I) 7(G) 13(M) 1(A).

Solution of My Running Key Challenge

The running key challenge I posted the other day has already been solved by Matthew Brown. He reavealed a lot more than 20 consecutive words I required. He is confident that he could eventually retrieve the entire message, though it would be quite time consuming.

His solution by a dictionary attack (importantly, using only long words) to find candidates followed by manually extending the fragments obtained would be the best practical approach for the time. Congratulations!

For more details, see the updated article, "Solving Running Key Ciphers (Manually/Digitally)".