01 The letter
| Shelfmark | BnF Français 3758 · Châtillon, 3 August 1635 |
|---|---|
| Sender | Châtillon |
| Recipient | Servien |
| Date | 3 août 1635 |
| Language | French |
| Report status | 10/10 pages transcribed; 4/4 cipher pages deciphered |
| Ciphertext | 666 written positions, 624 identified (93.7%); one group boundary uncertain. |
02 The key
78 signs: 56 letter signs, 20 in nomenclature, 2 repeat controls.
03 The decipherment
f127v, cipher continuation
Cette consideration les pourra empescher de s’engager si avant, mais Je Vous respon que nous ne jouons point de ruse cete fois, mais nous passons le Rhin pour nostre plus grande seurete afin d’avoir se grand fleuve entre les ennemis et nous.
Translation. This consideration may prevent them from advancing so far; but I assure you that we are playing no trick this time. We cross the Rhine for our greater safety, in order to have this great river between the enemy and ourselves.
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
- Plaintext in the same volume: f123v for f124r; f126r for f126v–127r; f127r for f127v.
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: none (no Gallica link in dossier; fr. 3758 ark not found offline, gallica.bnf.fr behind Cloudflare)
- Folio matches the report: unclear; cipher present: yes
- What we checked: his f127v crop: clear "mais Je Vous respon que" then 95(nous)...46(ennemi)...33(de)... codes consistent with his table, but sign-level read of 8+ symbols from the small crop was not reliable
- Verdict: partly confirmed (method key recovered based on adjacent plaintext, extent partial). The check is a sample, not a re-solution.
- Notes: Plaintext of the same letters elsewhere in the volume (f123v, f126r, f127r). 93.7% identified. Repo CATALOGUE lists Chatillon-Servien fr. 3758 nos.100,104 (ark btv1b9059471x?).
06 Notes and corrections
Fr. 3758 is also part of targets/rohan1636.
07 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. 86; his other items are listed on his contributor card.
- The working folder:
targets/chatillon1635/(his entry as extracted from the report, our spot-check,profile.json).