A 1542 papal letter from Cardinal Alessandro Farnese to nuncio Giovanni Poggio, containing a cipher section of 6,577 digits across multiple pages, was cracked using simulated annealing after remaining unsolved for decades on cipher puzzle platforms.
Researchers successfully decrypted a German Army Enigma message from July 10, 1941, requesting a route of march and immediate radio response. The message was recovered by identifying repeated plaintext phrases and machine settings, revealing the sender's location as Rosenow and signature as Waschbusch.
Researchers using Claude solved the century-old Chinese gold bar cipher mystery by proving the 1933 Shanghai bars were never encrypted at all—the 263 letters were deliberately arranged with perfectly uniform frequency distribution, which no actual cipher could produce. The case, unsolved for 30 years on cryptography lists, demonstrates statistical analysis can identify non-ciphers.
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.