Claude Fable 5.1 Cracks a 370-Year-Old Cipher in 44 Minutes That Stumped Humans for Centuries
zainhas · x · 2026-09-14
Claude Fable 5.1 independently solved the Cyphral Distich, an unsolved 370-year-old cipher
Vals.ai gave the model an open task: decode the two-line, 64-number cryptogram Sir Thomas Urquhart left at the end of his Logopandecteision. The cipher was posed as an open problem in Notes and Queries in 1899 and later listed in Klaus Schmeh's Top 50 unsolved encrypted messages; human attempts using frequency analysis, substitution, and homophonic substitution all failed.
How it cracked it:
- 44 minutes, 176k tokens, zero human interjection
- Key realizations: the cryptogram sits right after Urquhart's "32 Proquiritations," with the author pointedly emphasizing the number 32, plus a textual hint in the accompanying poem
- The clues were "surprisingly easy" — humans had simply missed them, making the solution embarrassing in hindsight
Related event: Claude Fable 5.1 Cracks 370-Year-Old Cipher(4 posts)→
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