Working notes · September 2026

Unsolved ciphers

Attempts on historical ciphers that are short, context-rich, and listed as unsolved. Started after Vals AI reported Claude Fable 5.1 reading Thomas Urquhart's Cyphral Distich; the question was whether the same approach, an agent plus a person checking its work, gets anywhere on the rest of the list.

Ferdinand correspondence

Brussels / Vienna, 16 November 1635 and 22 February 1640

Substantially deciphered · residual gaps

Winter quarters at Trier, recruitment in Westphalia, and a request for 100,000 florins. A known Latin draft supplies the 1635 alphabet; a separate syllable supplement extends the reading through both 1640 pages. Uncertain glyphs and copying errors remain explicit.

Ciphertext, Latin and English

Readings, key evidence, transcriptions and decoder.

Carta en cifra de Venecia

Ottobon to Mocenigo, 27 April 1589 · BNE Mss/994, ff. 34–38

Substantially deciphered

A Venetian dispatch to the ambassador in France, with the enclosed reply to Henri III's envoy Gondi, who had come to ask for aid and a league. The Republic's surviving key, Ziffra prima, reads all seven cipher pages. Intercepted in Savoy in 1589 and broken then by Philip II's cipher secretary, whose working was lost.

Page-by-page reading

Manuscript images, Italian and English side by side. Write-up, transcription, key excerpt and decoder.

Les voyes de prudence

Sir Richard Forster, 13 May 1644 · AD Val-d'Oise, 68 H 8

Deciphered

A ciphered passage in a letter by the treasurer of Henrietta Maria's household: counsel that preserving one's life is no failing before God. Mixed letter-and-number homophonic substitution, 207 symbols, three repairs. George Lasry and Norbert Biermann had read it earlier, and Robert Pitt published a key on 14 September 2026.

Ciphertext, French and English

With the 37 cipher words and the key. Write-up, solver and verification.

The Regent's postscript

Moray to John Wood, Edinburgh, 13 July 1568 · BL Add MS 32091 f. 213v

Substantially deciphered

Four ciphered lines at the foot of a letter to the Regent's agent at Elizabeth's court, on the day Mary was moved out of Carlisle: her being allowed to stay there, and the sending home of Lord Fleming, "hes done greit evil"; the warning about her return remains partly unread. The conjectural ending “as our friends know” requires an unexplained sign to be omitted. A simple substitution with homophones and word-signs, read from the page image; two person-signs and the last word open.

Cipher, Scots and English

Write-up, transcription, key, verification.

Chiffre aus Paris

Starhemberg, Paris, 23 May 1758 · Cryptiana transcription

Partially deciphered

A numerical cipher letter from Austria's ambassador at Versailles on drawing Spain into the Seven Years' War: the memorandum handed to Wall, Minorca as the price, a courier named Zinner. The 1752 Prima/Secunda key (DECODE R1695, R1698) gives connected German across the letter, but with no image of the original several joins do not parse and the exact full text is open.

Cipher rows, German and English

With the baseline key output, the proposed repairs and the checks. Write-up, keys, scripts and audit.

Also in the repository