01 The letter
| Shelfmark | BnF Français 5160 |
|---|---|
| Sender | de Loménie Brienne |
| Recipient | Servien |
| Date | 10 January and 1 August 1653; letter B undated in selected cipher pages |
| Language | French |
| Report status | 14/14 pages transcribed; 13/13 cipher pages deciphered |
| Ciphertext | 1,356 elements, 1,308 identified (96.5%); 40 nulls ?, 3 unidentified, 5 cancelled |
02 The key
136 symbols/codes: 25 letter signs, 101 in nomenclature, 7 nulls ?, 3 unidentified
03 The decipherment
f18r
Les sages en jugent autrement je m’en remettray à leurs sentimens. Pour avoir droit de se plaindre du duc de Mantoue des graces qu'il depart aux Espagnols, il faudroit l'en rechercher de semblables ou de quipolentes, et sy il s'y rendoit difficile on pouroit avec justice luy reprocher sa conduitte. Mais de luy imputer…
Translation. The wise judge otherwise; I will defer to their judgment. To complain about the Duke of Mantua’s favors to the Spaniards, one would have to ask him for similar or equivalent favors; if he proved reluctant, one could then justly reproach his conduct. But to impute to him…
04 Plaintext and other sources
Where a decipherment or clear copy already existed, as George Lasry gives it:
- Plaintext in another folio of the same volume
- Same volume: literal plaintext of letter B at f10r; literal plaintext of letter C at ff17r–v. Letter A uses the same key.
05 Our check
This result is George Lasry’s. This project did not re-solve the cipher: it checked one sample against the Gallica image and recorded what it found.
- Batch B. Image checked: https://openapi.bnf.fr/iiif/image/v3/ark:/12148/btv1b9060495t/f24/full/1600,/0/default.jpg
- Folio matches the report: yes; cipher present: yes
- What we checked: f9r (canvas 24) after "ordres que vous avez receu": 36 60 33 n 39 x 21 , 6 28 ... -> de la co-n-du-i-te , que vo... = "de la conduite que vo(us)" with his table (36=de,60=la,33=co,39=du,21=te,6bar=que,28bar=vo); fits the f10r plaintext context. Excerpt f18r not imaged by me.
- Verdict: confirmed (method key recovered based on adjacent plaintext, extent complete). The check is a sample, not a re-solution.
- Notes: Clear copies of letters B and C in same volume (f10r, ff17r-v). 96.5% incl. 40 probable nulls; several nomenclator values marked ?. 1653 consistent (Bordeaux fell Jul/Aug 1653).
06 Sources
- George Lasry, with ChatGPT Astra 6 and Anthropic Opus 5.5, BnF cipher research, 10 October 2026 (sent to Daniel Bourdeau on 13 October 2026 for publication here), p. 95; his other items are listed on his contributor card.
- image checked in the spot-check
- The working folder:
targets/brienne5160/(his entry as extracted from the report, our spot-check,profile.json).