Claude Fable 5.1 Solves the Cyphral Distich, a 370-year-old cipher
The AI model Claude Fable 5.1 has successfully deciphered the 370-year-old Cyphral Distich, a cryptogram from Sir Thomas Urquhart’s Logopandecteision. The model solved the puzzle by identifying contextual clues in the author's surrounding text that human researchers had previously overlooked.
Why it matters
This demonstrates the growing capability of large language models to perform complex historical research and pattern recognition tasks that have stumped human experts for centuries.
We gave Claude Fable 5.1 an open task: solve Sir Thomas Urquhart’s Cyphral Distich. It appears to have actually solved it, and the solution is quite embarrassing for humans in hindsight.
At the end of Urquhart’s Logopandecteision is a cryptogram consisting of two lines of 32 numbers each, called the Cyphral Distich . A cryptogram is a short message deliberately encoded so it can’t be read without knowing the rule that produced it. Here the entire puzzle input is these 64 numbers, and the goal is to recover the hidden plaintext:
5.3.27.38.32.14.21.8.66.8.70.39.5.9.12.18.2.3.56.5.1.7.3.2.13.19.3.25.9.3.16.6. 25.15.13.6.11.20.5.1.2.12.1.20.20.49.20.20.35.33.4.6.8.35.5.33.5.5.18.10.3.11.32.42. This cipher has remained seemingly unsolved for centuries. It was posed as an open problem in Notes and Queries in 1899, appeared again in 20th-century cryptography literature, and was later listed by historical-cipher researcher Klaus Schmeh among his Top 50 unsolved encrypted messages.
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