01 The letter
| Shelfmark | BnF Dupuy 155 |
|---|---|
| Sender | Francesco Guicciardini? |
| Recipient | Ferdinando I de Medici, Grand Duke of Tuscany |
| Date | 10 May 1597 |
| Language | Italian |
| Report status | 2/9 pages transcribed; 1 more in part; 2/9 pages deciphered; 1 more in part |
| Ciphertext | Transcribed passages: 1,952 elements, 1,946 identified |
02 The key
41 codes: 20 letter signs, 19 in nomenclature, 2 unidentified
- Key elsewhere
- Different volume: Dupuy 63, f48 (23 April 1597). Cryptiana's reconstructed key matches 27 values in the two transcribed pages.
03 The decipherment
f41r, rows9-14
[ante]cessore et nel mio. Et se Vostra Altezza nel principio fusse contentata di por quel luogo in mano di una terza persona confidente anbe le parti, perche lo conservassi a che fusse stato legitimo et Catolico Re di Francia, come da Sua Maesta ella ne fu richiesta, che si saria rimediato a molti inconvenienti et non sariano nati li a[ccidenti].
Translation. ...my predecessor and in my own time. And if Your Highness had initially agreed to put that fortress in the hands of a third person trusted by both sides, to preserve it for whoever became the legitimate Catholic King of France, as His Majesty had requested, many difficulties could have been remedied and those incidents would not have arisen.
04 Plaintext and other sources
Where a decipherment or clear copy already existed, as George Lasry gives it:
- Interlinear plaintext
- Interlinear Italian plaintext on the same pages.
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 A. Image checked: https://gallica.bnf.fr/ark:/12148/btv1b10034035f/f77.item
- Folio matches the report: yes; cipher present: yes
- What we checked: f41r "Inserto alla lettera de X di maggio 1597", numeric cipher with full interlinear Italian: "et se V.A. nel principio si fusse contentata di por quel luogo in mano di una terza persona confidente ad ambe le parti perche lo conservassi a chi fusse stato legitimo et Catolico Re di Francia" = his excerpt; numbers not re-decoded
- Verdict: confirmed (method key recovered based on adjacent plaintext, extent partial). The check is a sample, not a re-solution.
- Notes: Full contemporary interlinear decipherment on the page, plus Cryptiana key (Dupuy 63) - essentially an existing decipherment. Only 2/9 pages done. Sender "Guicciardini?" uncertain.
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. 55; his other items are listed on his contributor card.
- The working folder:
targets/dupuy155/(his entry as extracted from the report, our spot-check,profile.json).