Jacques Bongars (Wikipedia) represented Henry IV around 1593-1611 at the courts of imperial princes, striving to curtail the influence of the Hapsburgs.
BnF fr.7125-7132 ("Mémoires de Jacques Bongars") comprise papers related to Bongars. (I came to know of this by BnF's video on BnF fr.7129, "Le secret diplomatique en Allemagne au tournant du XVIIe siècle" (YouTube).)
For the interest of cryptography, the series is summarised as follows: BnF fr.7125 (no cipher found), BnF fr.7126 (many letters in cipher from 1594-1599), BnF fr.7127 (a few letters in cipher), BnF fr.7128 (no cipher found), BnF fr.7129 (many letters in cipher from 1600-1604, three original ciphers), BnF fr.7130 (no cipher found), BnF fr.7131 (many letters in cipher from 1605-1611, many original ciphers), BnF fr.7132 (no cipher found).
The present article describes many ciphers preserved in the series (called Bongars' Collection and numbered no.1, etc. herein for convenience's sake).
Full two pages of code words for names and common words.
This is used in a letter of 23 July 1609 of Henry IV (countersigned "Brulart", who succeeded Villeroy in 1606) in BnF fr.7131, f.120 ("Salomon" for "l'Arch. Albert", "Charlesmagne" for "le pape", "henry second" for "L'Empereur", "adrian" for "la maison d'Autriche", "Marin" for "les princes protestants", "Mathuu" for "le Roy d'Angleterre", "Robert" for "le Roy d'danemark", "Jocobabel" for "les Estats", "Babel" for "Les archiducs de flandres", etc.) along with the cipher of no.3 below. (I could not find "Senque" for "Neubourg", "Birthelmy" for "Brandenburg", etc. in the list. There may be addenda to the list.)
This is also used in Bongars' own letters including BnF fr.15579, f.104 along with the cipher of no.3 below. Entries such as "Adrian" for "la maison d'Autriche", "Henry troisieme" ["henry iiie" in the nomenclature] ("Roy d'Espagne"), etc. are used. "P. de Lippes" ("le roy de hongrie") may be included in addenda.
Cipher alphabet with Arabic figures and Latin letters. Two-digit figures with one dot below or two dots above for double letters (aa, bb, ...), syllables, and names. Use of two-digit figures with diacritics for syllables is a feature seen in Spanish cipher Cg.13 used around 1587-1592 (see another article).
Substitution alphabet includes "k", unlike many French ciphers, (but lacks "n"!). (In many handwriting specimens at the time, "5" is written in a single stroke like "S", but it is written in two strokes in this cipher.)
I have not seen an actual use of this cipher. According to Desenclos and Vial (2014) (n.4), this cipher was used at least in the first letters of Henry IV in 1594.
Cipher alphabet with Latin letters and other symbols. Graphic symbols, Latin letters with an umlaut, Arabic figures (6-99; 1-43 with an overbar) for names and common words.
Nulls. Symbols for doubling the preceding letter. Symbols for cancelling the preceding character. Symbols for cancelling characters inbetween. ("Chacun de ces caracteres doublera son prochain precedent." "Ceulx y l'adnulleront." "Et tout ce qui sera entre ces deux y sera nul.")
Variant forms to represent different letters in the substitution alphabet may confound (even authentic) decipherers. Someone (Bongars' clerk?) noticed this and created a table assorting similar symbols (BnF fr.7131, f.228).
This cipher is used in letters from Villeroy (Wikipedia) to Bongars in July to November 1604 (BnF fr.7129, f.253-f.268) and October 1605 to August 1611 (BnF fr.7131, f.19-f.219) and also in Bongars' letters (BnF fr.15579, f.104; BnF fr.15580 f.139, f.148, f.152, f.171, f.172).
This cipher can solve an undeciphered letter, dated 2 November 1604 and signed by Villeroy, in BnF fr.7129, f.268 (see below).
Symbols for words and names.
List of code words. "Le Cousin" for "Le Roy", "Lelio" for "Schonberg", "Lodvico" for "Fresnes", etc. (Apparently, f.226 was edited into f.225.) F.226v bears an endorsement "Chifre avec Mr Lobbetis[?]." (It is noteworthy that a list of code words without a cipher alphabet was called "chifre.")
Cipher alphabet with Arabic figures and some symbols. Symbols for names (Arabic figures 62-99, Capital letters, and other symbols).
Not only the cipher alphabet, but also the nomenclature provides for homophones ("62", "63", "64" for "Le Roy").
A deciphering aid (sorted by symbol similarity) for no.3 above.
Cipher alphabet with Arabic figures and other symbols. Symbols for names.
This was updated into no.17.
Symbols for some names.
The following lines (book titles?) are noted:
Code names in Latin.
Figure cipher (some figures with an overbar or an umlaut). Substitution alphabet with homophones for vowels. Nomencalture for names 34-99.
Cipher alphabet with symbols and Arabic figures. Nomenclature for names/titles (vi-xxiiii) and place names and common words (Arabic figures and symbols).
Symbols for doubling the preceding letter. Symbols for cancelling the preceding character. Nulls. Symbols for cancelling characters inbetween.
F.239r is a simple substitution alphabet (graphic symbols). Incorporated into no.15/no.26.
Symbols written in the margin seem to be meaningless. (One portion reads "xts/rqo/mig/eca," a reverse alphabet without BDFHLNPUYZ. Another portion includes some symbols not in the cipher alphabet.)
F.239v is a figure cipher (some figures with an overbar or an overdot). Each letter is assigned one figure, one figure with an overbar, and one symbol. Syllables with two-digit figures (with diacritics). Words and names. Some similarity with no.15/no.26.
This seems to be a pairing-based cipher alphabet (like one described by Porta) with a keyword "BONGARS". 2, 3, 4, 5, 6, 7, 8, 9 are nulls.
Cipher alphabet with symbols and Arabic figures. Each letter is assigned one figure, one figure with an overbar, and one symbol. Syllables with two-digit figures (with diacritics). Words and names. Compared with no.13, the nomenclature is similar (not the same), but more complete.
This appears to have developed from no.13 (substantially similar to f.239v, in which the symbols are replaced with those of f.239r and the syllables are reassigned).
Below is my reconstruction of this cipher made before I found the original cipher. This may serve as a (partial) deciphering table.
This cipher is used in many letters in 1594-1603 (BnF fr.7126, f.61-f.308 (1594-1597, 1599); BnF fr.7127, f.15, f.17 (duplicate) (1596), f.354 (1601?); BnF fr.7129, f.6-f.239 (January 1600 to January 1603). Of these, most are from Villeroy or Henry IV, but a few are from Henry de la Tour (Wikipedia) (BnF fr.7126, f.79, f.229, f.231, f.244) or Sancy (BnF fr.7126, f.85). The same cipher is also used in Bongars' own letters of 1602 in BnF fr.15577 (Gallica) (f.75 (not signed?), f.77, f.175, f.185, f.247, f.296, f.300, f.322, f.330) (Actually, I first used these letters for my reconstruction.).
The ciphertext BnF fr.7126, f.81 and f.83, which turned out to be duplicates of f.134 and f.136, look dissimilar to others because the spacing between digits is relatively even, making the units of two digits less visible.
No.26 is a cleaned version of this cipher.
Cipher alphabet with symbols and Arabic figures. Names and words. Nulls. A symbol to double the preceding letter and a symbol to cancel the preceding character.
Used in an unsolved ciphertext in BnF fr.7131, f.256, dated 8 February 1603 and signed Beaumont (see below).
Cipher alphabet with symbols and Arabic figures. Syllables with Arabic figures (some are with an overbar). Symbols for names and a few words.
A note on f.246v "faict le 26 Nouembre, 1590 / stile antien" must be referring to the portion without the syllables, which are added in the margin.
Some symbols in the nomenclature are re-assigned names. For example, "Mareschal de Biron" is struck out and replaced with "Administration de Magdebourg." No.8 is the version before these changes and the addition of the syllable table. No.18 and no.23 are the version that reflects these changes.
Used in BnF fr.7126, f.21 and f.22 (f.22 is a duplicate of f.21, but is differently enciphered), dated 7 March 1594, and BnF fr.7131, f.583, dated 15 February 1594. The undeciphered portion of the latter (of which I cannot read the signature) can be read "ce quil tient de le...", "deux cent mille flori..." etc.). This shows the cipher of no.8 in the ancient style made in 1590 had been updated into no.17 at least as early as 1594.
Moreover, this can solve an undeciphered letter, dated 8 February 1603 and signed Beaumont, in BnF fr.7131, f.256 (see below).
Cleaned version of no.17.
List of code names.
List of code names.
A few lines of note?
Figure cipher. Syllables. Nomenclature for some names.
The endorsement on f.253v partially reads "Fresne." That on f.254 reads something like "avec Mons. de Sancy".
Cleaned version of no.17.
A letter mostly in cipher (no.16), undeciphered. See below.
Figure cipher. Syllables and some short words are assigned two-digit figures with a middle dot or an underdot. For example, "49" is "i", but "4.9" with a middle dot is "de" and "49" with an underdot is "pri."
F.257v is a small nomenclature with names.
Substitution alphabet includes "k", unlike many French ciphers.
Cleaned version of no.15.
List of code words.
Figure cipher. Each letter is represented with a single digit (with an additional stroke). Figures 21-76 with a tilde represent names.
The instruction tells the digits should be written in groups of two (presumably to mislead would-be codebreakers).
The instruction also advises inserting Latin words for further dissimulation.
Cipher alphabet, with each letter represented with a single digit with various diacritics. Syllables with 10-99. Double letters and diphthongs are provided. More than a full page of nomenclature mostly with arbitrary symbols.
A duplicate of f.21, though differently enciphered.
This turned out to be a duplicate of f.134 (deciphered).
This turned out to be a duplicate of f.136 (deciphered).
There are a few symbols. It is not clear whether they are ciphers.
Dated 2 November 1604 and signed by Villeroy.
Can be deciphered with Bongars' cipher no.3.
Dated 8 February 1603 and signed Beaumont. Addressed to Bongars in Frankfurt. Can be (for the most part) deciphered with Bongars' cipher no.16. (From the few interlined letters, someone must have been aware that the symbol for "r" is unique to this cipher.)
One portion of the plaintext turned out to be a Latin phrase "Sabini sumniant quad volunt" (The Sabines dream what they will.).
Dated 15 February 1594. (I cannot read the signature. It's not De Neufville.) Cipher (no.17) is very modestly used.
Some portions can be read "ce quil tient de le...", "deux cent mille flori..." etc.).
S. Tomokiyo, "Development of Ciphers under Henry IV of France: A Case of Jacques Bongars: 1590-1611" (Academia.edu), which focuses on some ciphers used between Bongars and the court, is an initial attempt to contextualize Bongars' ciphers.
After uploading this article, I found the follownig scholarly treatment of the same materials:
Camille Desenclos and Charles-Éloi Vial (2014), "La parole diplomatique sous Henri IV à travers les mémoires de Jacques Bongars", Revue de la Bibliothéque nationale de France (Academia.edu)
The following (which is cited in the above article, but which I have not seen) also seems relevant.
C. Desenclos, "Les mots du pouvoir: la communication politique de la France dans le Saint-Empire au début de la guerre de Trente Ans (1617-1624)", th. de doct., histoire, sous la dir. d'O. Poncet, École nationale des chartes / Paris IV-Sorbonne.
Later on (August 2020), I found further details are described in Camille Desenclos, "Transposer pour mieux transporter, Pratiques du chiffre dans les correspondances diplomatiques du premier xviie siècle", in Matière à &ecute;crire (2017)