Decipherment of Hitherto Unsolved Historical Ciphers (by George Lasry)

I collect unsolved historical ciphers in a separate article, to which I receive or find solutions from time to time. In May 2022, I received solutions of no less than 10 ciphers from George Lasry, a computer scientist and expert in cryptanalysis, who has solved many historical ciphers (some of which I mentioned). (It seems his solver can readily solve any cipher mainly based on letter-by-letter substitution, even with many homophones. I guess the most time-consuming process in his codebreaking is preparing a transcription to be fed to the algorithm, for which he developed a tool to assist manual work.) While there remain some unknown or uncertain symbols, his decipherments seem to generally make sense.

The following presents his solutions (key & decipherment) in chronological order.

(Within a month after the first batch, I received additional solutions (also included in the following), which doubled the number to 21.)

Francis I

See another article for ciphers during Francis I's reign.

Bayonne's Cipher (1528-1529)

BnF Clair. 329(Gallica), f.9 is annotated as Bayonne's. As seen in the images below, it uses a cipher different from a known cipher used by Bayonne in f.139 (1529).

The same key also fits Clair. 328, f.291 (Bayonne to Montmorency, 28 October 1528). Since this letter is printed in Ambassades en Angleterre de Jean Du Bellay (from BnF fr.3077, p.145-147; the beginning of f.291v corresponds to the last paragraph on p.432 of vol.1 (Google)), comparison may reveal more symbols.

I could not find the letter of Clair. 329 in the printed edition. But since the editor was aware of Clairambault 330 (p.7, n.3; p.118, n.2), it may be simply that I overlooked it.

Grammont's Cipher (1529)

BnF Clair.330 (Gallica), f.53 is a letter from Mr. de Gramont, Bishop of Tarbe (Wikipedia), to Montmorency (Rome[?], 5 October 1529). It uses a cipher different from a known cipher used in 1530.

(In 1525, the Bishop of Tarbe had been despatched by Queen Regent, Louise of Savoy, (mother of Francis I) to obtain the freedom of the king in captivity in Spain. Then, he was sent to England to encourage Henry VIII to divorce Catherine of Aragon. Then, he was sent as ambassador to Rome.)

French Marshals and Charles Hémard de Denonville (Bishop of Mâcon)

BnF fr.3081 (Gallica), f.41, is a letter wholly in cipher ("Dupplicata des articles envoyez par messrs les marechaulx françoys au roy"). It is solved as follows.

George found the same key is applicable to BnF Dupuy 265 (Gallica), f.132, which is a letter from Bishop of Mâcon to the king (29 May 1535) according to catalogue information. Its beginning can be read as follows.

Although the marshals' letter is filed with letters from the 1520s, it may also be from ca. 1535. Mâcon was ambassador in Rome from 1534 to May 1538. I wonder whether it has something to do with the Italian War of 1536-1538 (Wikipedia). Historian's help is needed to find out how the same cipher came to be used by the marshals and the bishop.

Henry II

See another article for ciphers during the reign of Henry II of France.

?Cipher of Philibert de Babou de la Bourdaisiere with His Son

BnF Dupuy 44 (Gallica) has a ciphertext (f.39), which, according to the catalogue information, corresponds to a decipherment (f.40), a letter of Philibert Babou de la Bourdaisiere (c. 1484-1557) (Wikipedia) from his son, Philibert (made cardinal in 1561) (Wikipedia).

With this pair of ciphertext and plaintext, I could not reconstruct the cipher. To me, the plaintext (containing about 3000 letters according to my very rough counting) seemed too long for the neatly written ciphertext (about 1000 letters). George Lasry's solution now made it clear that the ciphertext is independent from the plaintext letter. Now it is interesting to see to whom the ciphertext should be attributed.

Charles Marillac - Du Bellay (Bayonne) (1550)

BnF Dupuy 265 (Gallica) contains several cipher texts, which Paul Friedmann used to reconstruct some ciphers (see another article). George Lasry noted the cipher f.101 is left undeciphered and solved it as follows. According to catalogue information, it is a letter of Charles Marillac, ambassador in Germany, to cardinal Jean Du Bellay (Bishop of Bayonne), Augsburg, 18 November 1550.

Montmorency - Du Bellay (Bayonne)

BnF Dupuy 265 (Gallica) also contains an undeciphered letter from Montmorency to cardinal Du Bellay (f.228-238). It is solved as follows. (This may be the same as f.231 in Paul Friedmann's list.)

Nicolas Raince - Du Bellay (Bayonne)

BnF Dupuy 265 (Gallica) also contains an undeciphered letter from Nicolas Raince, resident in Rome, to cardinal Du Bellay (f.336) (not in Paul Friedmann's list). It is solved as follows despite the shortness of the ciphertext. The cipher turned out to be monoalphabetic.

Claude de la Guiche, Bishop of Mirepois (1551)

BnF fr.3138 (Gallica), f.59, is a letter from Claude de la Guiche, Bishop of Mirepois, to Montmorency (Rome, 22 November 1551) (which was not in my list). The cipher is solved as follows.

The volume contains more ciphertexts already deciphered.

Charles IX, Henry III

See another article for ciphers during the reigns of Charles IX and Henry III.

Hurault, Ambassador in Venice (ca.1564?)

A letter (BnF Colbert 395, p.335) from Jean Hurault[?], French ambassador in Venice, is solved as follows. (As it turned out, the plaintext is in p.337, which generally proves the accuracy of the solution and will allow identifying a few more symbols.)

Charles IX to Philibert du Croc (1565-1567 or 1572)

A letter in cipher from Charles IX to Philibert du Croc is reproduced in Paul Destray (1924), Un diplomate français du XVIe siècle: Philibert du Croc (Gallica) (p.80 and the next leaf). Although the letter is not dated, the endorsement indicates Philibert du Croc was then ambassador in Scotland. See another article for contemporary ciphers.

This is solved as follows.

A Letter to the King in BnF fr.3254

A letter "to the King" in BnF fr.3254 (Gallica), f.76, is almost entirely in cipher. (This was not in my list.) The volume contains many letters of Charles IX or Catherine de Medicis to Matignon and others from 1570-1573 and a copy of one letter of François de Cornelian, bishop of Roddez from 1583.

This is solved as follows.

Duke of Guise? in BnF fr.15564 and fr.15565

There are letters to Mr de Mercoeur probably from the Duke of Guise in BnF fr.15564 (Gallica), f.27, f.78, f.119, f.142 The same cipher is used in letters "probablement de princes de la maison de Guise" in BnF fr.15565 (Gallica), f.105, f.122.

The solution is as follows. (The nomenclature symbols appear to be Roman numerals.)

Other Letters in BnF fr.15565

The cipher used in letters in BnF fr.15565, f.7, f.62, and f.91 are deciphered as follows.

A Letter in BnF fr.15566

(Gallica), f.50, is solved as follows. (The solution is preliminary because the ciphertext is too short.)

Villeroi to Henry III (1577)

A letter in cipher from Villeroi to Henry III of France was sold at an auction. It is wholly in cipher except for the complimentary ending: "Sire ie prie dieu conserver vre mté en parfaicte santé / De Bergerac ce viiie jour de sepbre 1577" and the signature "Vre très humble très obéissant & très obligé subjet & serviteur. Deneufville" in Villeroi's hand. (The date is shortly before the Treaty of Bergerac (Wikipedia) was made between the King and the Huguenot princes.)

This is solved as follows. (I had made a try by using some interlinear decipherment, but was unsuccessful (my blog).

An Unsigned Letter in BnF fr.15572 (1586)

An unsigned letter, wholly enciphered, dated January 1586 is in BnF fr.15572, f.43 (see another article). It is solved as follows.

BnF fr. 15573

The cipher used in a letter of Duval to Villeroi in f.127 of BnF fr.15573 (Gallica) is solved as follows. It appears to be a sequel of f.124 (the intervening f.126 is another letter), which is by René Duval, Sr de Stors according to catalogue and in which the key below reveals words such as "j'estim", "promect", "au[x] les forces leur ... agreable".

A Letter to(?) Pasquier in BnF fr.4712 (1592)

A letter partly in cipher to(?) "Monsieur Pasquier Lrre[?] des finances" (?Wikipedia) (1592) is in BnF fr.4712, f.35 (see another article). (According to catalogue information, this is no.26 "Fragment de notes et reflexions sur la conduite a tenir par Henri III pour abattre "les huguenots".) It is solved as follows.

Louis XIII

See another article for ciphers during LouisXIII's reign.

Melchior de Sabran (1631)

BnF Baluze 155 (Gallica), f.79, contains a letter, dated Dijon, 28 March 1631, of Louis XIII (undersigned Bouthillier) to Melchior de Sabran, a diplomat then resident in Genoa (1630-1637). It has a paragraph in cipher. It is solved as follows.

George Lasry confirmed this cipher is also used for many letters of Sabran in BnF fr.4134 and fr.4135.

?Odoardo Farnese, Duke of Parma (1637)

BnF Baluze 156 (Gallica), f.40, is wholly enciphered, undeciphered. It seems to be an enclosure of a letter (in French) of Odoardo [Édouard] Farnese, Duke of Parma (Wikipedia), to Sabran, dated Plaisance, 27 May 1637. It is solved as follows.


See another article for contemporary Spanish ciphers.

An Unidentified Cipher

A letter in cipher in BnF Espagnol 318 (Gallica) (f.122, no.95, 8 January 1497) is solved as follows (it is "approximate").

©2022 S.Tomokiyo
First posted on 29 May 2022. Last modified on 15 June 2022.
Articles on Historical Cryptography
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