Claude Fable 5.1 Solves 370-Year-Old Cyphral Distich Cipher in 44 Minutes
The solve leans on an internal clue Urquhart wrote into his own book rather than on external cryptanalysis, which is the kind of contextual reading that stalled human cryptographers on this text since it was posed as an unsolved problem in 1899.
Reporting from 1 source: GIGAZINE.
The AI model Claude Fable 5.1 deciphered the Cyphral Distich, a two-line cipher that had gone unread for over 370 years, in 44 minutes and 176,000 tokens. Researcher Gabe Jaffe wrote up the method. The cipher sits at the end of Sir Thomas Urquhart's 17th-century Logopandecteision, after a list of 32 "Proquiritations," and the model found the key in that number and the word "wish."
The rule Claude Fable 5.1 landed on: for the i-th number in the ciphertext, go to the i-th Proquiritation and take the first letter of the word at position n. The first number is 5, and the fifth word of the first Proquiritation is "of," giving "o."
Two findings drove the solve. The ciphertext sits directly after Urquhart's phrase "32 Proquiritations," and the number 32 recurs, so the model treated it as a key. The poem next to the cipher says an honest reader will find there "the wishes of his own heart and the author's thoughts," which pointed the search inside the book instead of outside it.
Synthesized by Yomimono from the 1 cited source below, including Japanese-language reporting where cited, then editorially reviewed before publishing.