Researchers used simulated annealing to decrypt a 500-year-old cipher from a 1542 letter sent by Cardinal Alessandro Farnese to the papal nuncio Giovanni Poggio. The letter, stored in the Vatican Archives, contained a polyalphabetic substitution cipher that had remained unsolved until computational methods were applied to recover the key and plaintext.
Claude Fable 5.1 solved the Cyphral Distich, a 370-year-old cipher by Sir Thomas Urquhart that had remained unsolved for centuries. The solution uses the 32 Proquiritations in Urquhart's text as a key, where each number in the cipher line indexes a word whose first letter reveals the hidden message: a royalist prayer for King Charles II. Fable 5.1 also deciphered Urquhart's larger Cyphral Octastich using the same principle with numbered pages.
Claude Fable 5.1 solved a 370-year-old cipher in forty-four minutes, demonstrating AI capability in search-heavy cryptanalytic tasks. The achievement is presented as evidence of how modern AI excels at problems requiring extensive searching and testing.