From Vals · · 3m
A 370-year-old cipher, cracked in 44 minutes
Sir Thomas Urquhart hid a royalist prayer in his own book, and everyone spent centuries looking for the key outside it.
In brief
Sir Thomas Urquhart hid a royalist prayer in his own book, and everyone spent centuries looking for the key outside it. The bottleneck on old unsolved puzzles was never cleverness, it was attention. That bottleneck is going away. Originally reported by Vals.
Sixty-four numbers, no answer
At the end of Urquhart's Logopandecteision sits a cryptogram: two lines of 32 numbers. The whole puzzle input is those 64 digits, and the plaintext was lost.
Unsolved since 1899
It was posed as an open problem in Notes and Queries in 1899, resurfaced in 20th-century cryptography books, and made Klaus Schmeh's list of the top 50 unsolved encrypted messages.
Every method failed
Codebreakers threw frequency analysis, substitution and homophonic substitution at it. None of them moved. They were all missing one easy clue.
Forty-four minutes, no help
Claude Fable 5.1 was given an open task and left alone. It burned 176k tokens, tried several approaches, and got there with zero interjections from the human.
The number 32, twice
The cipher is printed right after Urquhart's 32 Proquiritations, and he makes a point of stressing that number. Thirty-two paragraphs, 32 numbers per line.
“there can no number like that of two and thirty … be pitched upon”
The poem said wishes
The verse beside the cipher promises an honest reader will find "his own heart's wishes." The Proquiritations each end with "is the desire," "wish," or "hope of."
“his own heart's wishes, and the Author's minde”
The key was the book
Everyone assumed the key was an external cipher alphabet to be reconstructed. It wasn't. The i-th number means: go to the i-th Proquiritation, count that many words in, take the first letter.
A prayer for the king
Out comes a rhyming couplet: O GOD UPHOLD KING CHARLS THE SECOND AND / MAKE HIM THE SUPREME RULER OF THIS LAND. Exactly 32 letters a line, and-land rhyme intact.
It checks itself
The fit is self-verifying. The letter counts match, the lines rhyme as a distich should, and Urquhart was a committed Royalist, so a hidden prayer for Charles II fits his politics.
Then the bigger one fell
Urquhart left a second cipher in The Jewel (1652): 285 numbers, also unsolved. The Jewel has 284 numbered pages. Same trick, pages instead of paragraphs. Fable solved all but nine letters.
The gaps, stated plainly
Nine letters in line 5 decode to nonsense that no shift or lattice fixes, and "Irish" is spelled IRSH. Settling those needs a physical 1652 copy, since no free page images exist.
How it was elicited
Months of prompting other frontier models produced no verified solve. The winning nudge: aim at ciphers that are verifiable, skip the ones the CIA has already chewed on, think creatively.
Persistence, not genius
No extraordinary cryptanalysis happened here. The clue was simple and the model just kept looking until it found it. These puzzles were bottlenecked on human attention, and that bottleneck is lifting.
The headline
The bottleneck on old unsolved puzzles was never cleverness, it was attention. That bottleneck is going away.
