French Ciphers during the Reign of Francis I

French ciphers during the reign (1515-1547) of Francis I (François Ier) are described. His reign is interesting for the study of French ciphers because the earliest known French ciphers date from this period.

Throughout the reign, Francis was engaged in a series of wars with Holy Roman Emperor Charles V in the Italian Peninsula. Francis met a devastating defeat at the Battle of Pavia in February 1525, in which even the king himself was captured. It was only in March 1526 that he was released in exchange for his two sons. The first known specimens of French ciphers date from this period. (Of course, there would have been earlier use not yet found.)

Many of the letters mentioned below are addressed to Anne de Montmorency (1493-1567) (Wikipedia). He was a Marshal of France since 1522. He was captured at the Battle of Pavia with the King, but was released for ransom and negotiated for the settlement (Wikipedia) with the Emperor. On 26 March 1526 (right after the King's release), he was made Grand Master of France responsible for the supervision of the royal household and the king's private service. In 1538, he was made Constable of France (Wikipedia).

Jump to: BnF Clair.325 (1526), BnF fr.2984 (1526), BnF Clair.328 (1528), BnF Clair.329 (1529), BnF Clair.330 (1529), BnF Clair.331 (1530), BnF Clair.333 (1530), BnF Clair.312, BnF Clair.313, BnF fr.3005, BnF fr.2980 (1530), BnF fr.3019, BnF fr.3045 (1528, 1536), BnF fr.3053 (1535-1537)

BnF Clair.325 (1526)

The earliest use of cipher in France that I have found thus far is in BnF Clair.325 (Gallica), which is a volume for 1525-1526.


A postscript to a letter dated 25 September [1525 or 1526?] from Jean de Calvimont to Antoine Duprat (Wikipedia), chancellor of France and prime minister, is in an unsolved cipher.

Jean de Calvimont (Wikipedia) was sent as ambassador to Spain in 1526 to negotiate the ransom of the King's sons held in Spain as hostages in exchange for the King. (The content and the placename before the date ("Pallence"?) may help identify the year.)

In 2021, Norbert Biermann solved this cipher. Basically, it is a simple monoalphabetic substitution cipher. It revealed that f.65 of the same volume is the plaintext.


One passage in a letter dated 5 January 1526 from Bayard (?some relative of Chevalier Bayard, who had died in 1524 (Wikipedia)?) to Marechal de Montmorency is in an unsolved cipher. (The marginal note "jay respondu que je navoye veu icy nul homme de par vous"[?] seems irrelevant to the cipher.)

BnF fr.2984 (1526)

BnF fr.2984 (Gallica) contains letters in cipher dating from May to December 1526 by Nicolas Raince. These are the earliest specimens found in the French National Library (BnF) by Desenclos (2018), "Unsealing the Secret: Rebuilding the Renaissance French Cryptographic Sources (1530-1630)."

Raince was a secretary at the French embassy in Rome from ca. 1521 to 1537 (Jan Pendergrass (ed.), Jean de Pins, Letters and Letter Fragments (Google)) and acted like an ambassador (Catherine Fletcher, The Divorce of Henry VIII: The Untold Story from Inside the Vatican (Google)).

The cipher can be reconstructed as follows.

BnF Clair.328 (1528)



This is a letter dated Montcallier (Moncalieri?), 28 July [1528], from Guillaume Bochtel (Wikipedia) to Montmorency. The cipher used can be reconstructed as follows.


This is a letter dated Poudris[?], 28 October [1528], from Bishop of Bayonne to Montmorency. The cipher (called "Bayonne's Cipher (1528)" herein) was identified by George Lasry in 2022 (see another article).

Jean du Bellay, Bishop of Bayonne (Wikipedia), was ambassador to England in a series of missions in 1527-1534.

Bayonne's correspondence is compiled in Correspondance du cardinal Jean du Bellay, vol.1 1527-1529 (Google), vol.2 1535-1536 (Google), vol.3 1537-1547 (Google). This letter is printed in vol.1 (from BnF fr.3077, p.145-147; the beginning of f.291v corresponds to the last paragraph on p.432). Comparison may reveal more symbols..

BnF Clair.329 (1529)


F.9 is annotated as Bayonne's. In 2022, George Lasry solved the cipher (see another article), presented above as "Bayonne's Cipher (1528)."

F.10, mostly in cipher, can be read with Bayonne's Cipher (1529) below.

F.139, Bayonne's letter dated 30 June 1529, can be read with Bayonne's Cipher (1529).

BnF Clair.330 (1529)


The following three letters can be read with Bayonne's Cipher (1529).

f.16 (18 September 1529) Bishop of Bayonne to Montmorency

f.71 (London, 17 October 1529) Bishop of Bayonne to Montmorency

f.85 (London, 27 October 1529) Bishop of Bayonne to Montmorency (deciphered on the previous pdf page)

Gramont's Cipher (1529)

F.53 is a letter from Mr. de Gramont, Bishop of Tarbe (Wikipedia), to Montmorency (Rome[?], 5 October 1529). The cipher was broken by George Lasry in 2022 (see another article).

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.

f.206 (24 December 1529) Conte Guy [Guido] Rangone (British Museum) to Montmorency

BnF Clair.331 (1530)


There are three undeciphered letters in Italian.

f.15 (10 February 1530) Count Guido Rangone to Montmorency, 10 January 1530 (The cipher seems to be the same as the one used in BnF Clair.330 above.)

f.149 (13 March 1530) Signor Joachim to Montmorency

f.156 (15 March 1530) from London to the King or Montmorency

The third one is in a different style from others presented in this article. It is wondered whether Italian ciphers were shared with the French court at this time. The content seems to be a list of sums.

BnF Clair.333 (1530)


F.24 and f.27 are letters from Bishop of Bayonne to Montmorency (June 1530) in Bayonne's cipher (1529). (I mainly used these in my reconstruction above.)

BnF Clair.312 (undated pieces)


F.325 (London, 15 December) is a letter from Bishop of Bayonne to Montmorency in Bayonne's Cipher (1529).

BnF Clair.313 (undated pieces)


F.339 (London, 15 June) and f.343 are letters from Bishop of Bayonne to Montmorency in Bayonne's Cipher (1529).

BnF fr.3005


f.61 (no.25)

Letter of Bishop of Lodi, Murano (Wikipedia), 14 June 1529

The Bishop of Lodi at this time was Gerolamo Sansori from 1519 to 1536 according to The Hierarchy of the Catholic Church and Wikipedia, but Wikipedia says Ottaviano Maria Sforza was Bishop of Lodi from 1527 to 1530. It is necessary to read the text in Italian to determine which is the author of this letter.

In the following reconstruction, the three symbols for "m" would be variants in handwriting. That is, the substitution is monoalphabetic.

f.107 (no.44)

Letter about the project of marriage of Duke of Orleans (future Henry II) and madam d'Urbin (Catherine de Medici). The offer was made early in 1533 and the marriage took place in October 1533 (Wikipedia).

In the following reconstruction, the second symbols for "l", "p", "s" indicate double letters. The second symbol for "u" is a variant in handwriting.

f.165 (no.67)

Letter, dated London 22 October, of Bishop of Bayonne to Montmorency. Unsolved. In Bayonne's Cipher (1529).

BnF fr.2980 (1530)


f.29 (no.21) is a letter dated Rome, 20 May [1530], from Cardinal Gabriel de Gramont, Bishop of Tarbe, to Jean Breton, seigneur de Villandry, conseiller du roi, secretaire des finances (Presses universitaires de Rennes).

f.30 (no.22) is a letter dated Rome, 20 May 1530 from Cardinal Gabriel de Gramont, Bishop of Tarbe.

These undeciphered letters can be read with Gramont's cipher (1530) below.

BnF fr.3019


f.20 is a letter from Gabriel de Gramont to Grand Master, dated Rome, 31 August. The cipher (called Gramont's Cipher (1530) herein) can be reconstructed as follows.

f.73 is a letter Hieronimo Ranzo (see another article).

f.97 is catalogued as "GEORGES D'ARMAIGNAC, evesque de Roudez, DE SELVE, evesque de Lavaur... De Venze, ce XVIe novembre mil V.C.XXXVI", with a few words in cipher (Selve's cipher below).

BnF fr.3045 (1528, 1536)


f.28 (no.24)

Galeaz Vesconte [Galeazzo Visconti] to Angelo Bolano, dated Alexandria, 12 October 1528. Italian. Undeciphered. This looks different from other French ciphers. It may be an Italian cipher.

f.38 (no.29)

Robert Cenalis, Bishop of Avranches (Wikipedia), to Francis I, Venice, 13 October 1528

The cipher can be reconstructed as follows.

f.42-49 (no.31)

Georges de Selve, Bishop of Lavaur (Wikipedia), to Francis I, Venice, 5 July 1536

Selve was ambassador in Venice in 1535-1536.

The cipher can be reconstructed as follows.

BnF fr.3053 (1535-1537)

BnF fr.3053 (Gallica) contains many letters (1535-1537) partially in cipher from Charles de Hémard de Denonville , Bishop (Cardinal) of Mâcon [Mascon] (Wikipedia), ambassador in Rome, to Montmorency. (F.67 is from "messrs de Roudez et Lavaur" in Venice to the Cardinal of Macon, dated 9 February 1536.)

One fragment on f.85 uses a different cipher (deciphered on f.86).

(This is one of the first ciphers I reconstructed some years ago from BnF. It took some time to find a clue in this reconstruction. As always, reading the handwriting of the plaintext was the first obstacle. I barely recognized "vos mains" and "choses" near the end of the plaintext. Of these, "choses" also appears near the beginning of the plaintext. I looked for similar symbols around where the word "choses" should occur. Then, I found two succeeding symbols in common. Were these "ch", "ho", "os", "se", or "es"? Then, the next symbol to these near the ending was found to be the same as what should be "o" in "vos mains". This seemed promising. Now, I had "choses qui pas (some letters illegible to me) et vos mains." This revealed "toutes choses" near the beginning. After this, there was no real difficulty in the reconstruction.)

Another cipher of Cardinal of Macon, reconstructed below, is used in a letter from the cardinal to the king dated Rome, 15 February 1536 in BnF Dupuy 44 (Gallica) (f.30-38; f.31 is a decipherment of f.31bis; f.33 is a decipherment of the ciphertext starting from the second ciphertext block of f.32; f.35 is a decipherment of f.36; f.37 is a decipherment starting from the second ciphertext block of f.38).

Mascon's cipher from this period was also used by Jean de Langeac, Bishop of Limoges (Wikipedia), ambassador to Ferrare, in writing to Jean de Bellay, Bishop of Bayonne, who could ask Mascon to have it deciphered.

Le chiffre de la presente est celuy de monsr de Mascon; il luy plaira commander a son secretaire qu'il les dechiffre.
19 November 1535, Ferrare, Jean de Langeac to Jean de Bellay (BnF Dupuy f.96-98, BnF fr.19577, f.11) from Correspondance du Cardinal Jean du Bellay, vol.2, p.156

BnF fr.3081 (1520s/1530s?)

BnF fr.3081 (Gallica), f.41, is a letter wholly in cipher ("Dupplicata des articles envoyez par messrs les marechaulx françoys au roy"). George Lasry solved it in 2022 (see another article).

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.

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.

Further Sources

After posting this article, I found Paul Friedmann conducted similar reconstruction work. His keys are now preserved as NAF 4206 (which I have not seen). According to catalogue information, it covers the following:

Claude Dodieu de Vely, 1529 (ms. français 3020, fol. 103)

Le même, 1535 (Dupuy, 265, fol. 48)

Je. Joaquin de Vaulx, Gasparo Sarmanno, etc., 1528-1530 (ms. français 3096, fol. 113)

Je. Joaquin et l'évêque d'Avranches avec François Ier, 1529 (ms. français 3000, fol. 74)

Jean du Bellay et Anne de Montmorency, 1529 (ms. français 3077, fol. 114)

Jean du Bellay et Montmorency, 1534 (Dupuy 265, fol. 231)

Jean, cardinal du Bellay, et François Ier, 1535 (Dupuy, 265, fol. 253)

L'évêque de Limoges et le cardinal du Bellay (Ibid., fol. 97)

Le cardinal du Bellay et l'évêque de Mâcon, 1535 (Ibid., fol. 211)

Les mêmes, 1536 (Ibid., fol. 170)

Le cardinal de Gramont

L'évêque de Rodez et de Selve, évêque de Lavaur, avec François Ier, 1536, (ms. français 3019, fol. 97)

L'évêque d'Avranches, 1528 (ms. français 3045, fol. 38)

L'évêque de Mâcon et François Ier, 1534 (ms. français 3020, fol. 87)

François de Dinteville, évêque d'Auxerre, et Montmorency, 1533 (Dupuy, 547, fol. 97)

L'évêque d'Auxerre et Gilles de La Pommeraye, 1532 (Dupuy, 547, fol. 171)

L'évêque d'Auxerre et Lazare de Bayf, 1532 (Dupuy, 547, fol. 215.)

L'évêque d'Auxerre et le marquis de Saluces, 1532(Dupuy, 547, fol. 157)

Le cardinal de Ferrare et Henri II, 1549 (ms. français 3126).

See also my related articles:

French ciphers during the Reign of Henry II of France

©2020 S.Tomokiyo
First posted on 2 November 2020. Last modified on 11 June 2022.
Articles on Historical Cryptography
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