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AI & Machine Learning
Sep 13, 2026

Claude Fable 5.1 Deciphers 370-Year-Old Cyphral Distich Cipher

Sep 13, 2026
AI Summary

Claude Fable 5.1 has successfully solved the Cyphral Distich, a cryptogram created by Sir Thomas Urquhart in the 17th century. The solution reveals a royalist prayer for Charles II, highlighting the model's ability to tackle historical cryptographic challenges that have stumped humans for centuries.

The Cyphral Distich consists of 64 numbers and has remained unsolved for over 370 years.

Claude Fable 5.1 solved the cipher in 44 minutes by recognizing that the key was embedded within Urquhart's own text, specifically the 32 Proquiritations.

The solution revealed a prayer for Charles II, aligning with Urquhart's royalist sentiments.

Fable 5.1 also deciphered a larger related cryptogram, the Cyphral Octastich, using a similar method based on the structure of Urquhart's work.

The successful decryption demonstrates the potential of AI models in solving historical mysteries that have previously challenged human cryptographers.

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