Fable 5.1 Apparently Cracked a 370-Year-Old Cipher in 44 Minutes
A 370-year-old cryptogram of 64 numbers, solved in 44 minutes by Fable 5.1 — with a hedge in the write-up that makes the claim worth checking.
Two lines of 32 numbers each, 64 in total, sit at the end of Sir Thomas Urquhart’s Logopandecteision, and had gone unread for 370 years. Claude Fable 5.1 finished the puzzle in 44 minutes on 176k tokens, with zero interjections from the person who set the task. The solution, they say, is embarrassing for humans in hindsight.
The Cyphral Distich was posed as an open problem in Notes and Queries in 1899, appeared again in 20th-century cryptography literature, and was later listed by Klaus Schmeh among his Top 50 unsolved encrypted messages. Frequency analysis, substitution, homophonic substitution — all tried, none worked. Fable 5.1 got there through two observations. The cryptogram is printed immediately after Urquhart’s 32 Proquiritations, a count he goes out of his way to stress. And the poem accompanying the cipher promises that an honest reader will find in it his own heart’s wishes and the author’s mind, while the Proquiritations themselves keep concluding on desire, wish, or hope.
The second observation is a reading of the preface, not a break in the arithmetic. That is also why the claim wants a second pair of eyes: the write-up hedges in its own summary sentence, saying the cipher appears solved. A 370-year-old puzzle that gives way to close attention on the page it sits on is exactly the kind of result worth reproducing before it hardens into trivia.
What surprised me is the shape of the solve — the hint was in plain print beside the numbers the whole time, and a century of substitution tables missed it. Write out the 64 numbers, read the 32 Proquiritations, and see whether the same rule falls out.