01 The letter
| Shelfmark | BnF Dupuy 468 |
|---|---|
| Sender | Ernestus dux and Joachimus; probably Ernst of Brunswick-Lüneburg and Joachim von Maltzan |
| Recipient | Francis I, King of France |
| Date | Eve of Saint Paul, at five in the morning; no year. Context suggests c.1518–1520;1519 remains plausible. |
| Language | Latin |
| Report status | 2/3 pages transcribed; 1 more in part; 2/2 cipher pages deciphered |
| Ciphertext | 684 elements, 660 identified (96.5%) |
02 The key
30 symbols, 20 letter signs, 6 in nomenclature, 3 nulls?, 1 unidentified
03 The decipherment
f28r, final four cipher lines
Tunc optimum erit ut christianissimus hoc fedus petat velle inire; hoc modo etiam si aliquando noluissent esse in federe cu[m] christianissimo, hoc modo astricti erunt esse confederatores christianissimi.
Translation. Then it will be best for the Most Christian King to ask to join this alliance. In this way, even if some had not wished to ally themselves with him, they will be bound to become his allies.
04 Plaintext and other sources
Where a decipherment or clear copy already existed, as George Lasry gives it:
- Interlinear plaintext
- Interlinear decipherment accompanies most cipher runs on f28r–v,PDF65– 66/Gallica63–64.
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/btv1b10035959t/f63/full/1600,/0/default.jpg
- Folio matches the report: yes; cipher present: yes
- What we checked: f28r l.2 V.⊔.ч.4.V.T.cc.m -> i n o p i d u m = "in oppidum" (interlinear agrees); signs match his table (i=V,n=⊔,o=ч,p=4,d=T,u=cc,m)
- Verdict: confirmed (method key recovered based on adjacent plaintext, extent complete). The check is a sample, not a re-solution.
- Notes: Addressed Christianissime rex, signed Ernestus/Joachimus; interlinear on most runs; 96.5% identified, 2/2 cipher pages; 1 page only partly transcribed (clear text). Date c.1519 is his inference.
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. 77; his other items are listed on his contributor card.
- image checked in the spot-check
- The working folder:
targets/dupuy468/(his entry as extracted from the report, our spot-check,profile.json).