Fable 5.1 Solves 370-Year-Old Cyphral Distich Cipher in 44 Minutes

The Unsolved Cyphral Distich

Sir Thomas Urquhart’s Cyphral Distich, a cryptogram consisting of two lines of 32 numbers each, has remained unsolved for centuries. It was presented as an open problem in 1899 and listed among the Top 50 unsolved encrypted messages by historical-cipher researcher Klaus Schmeh. Previous attempts by human cryptographers using methods like frequency analysis and substitution were unsuccessful.

Fable 5.1's Breakthrough

Fable 5.1, an AI model, was given the task of solving the cipher. After 44 minutes and processing 176,000 tokens, the AI arrived at a solution without human intervention. The AI's success stemmed from two key realizations that human attempts had missed.

Identifying the Internal Key

The first realization was the significance of Urquhart's '32 Proquiritations', which immediately preceded the cryptogram. Urquhart himself emphasized the number 32. The second clue came from a poem accompanying the cipher, which suggested the reader would find 'his own heart’s wishes, and the Author’s minde', aligning with the 'wish' or 'desire' formulations in the Proquiritations.

These clues led Fable 5.1 to deduce that the key was not an external cipher alphabet but was embedded within the book itself. The rule was to take the i-th number in a cipher line, go to the i-th Proquiritation, use that number as a word index, and extract the first letter of that word.

Significance for Cryptography and AI

The successful decryption by Fable 5.1 highlights the AI's ability to identify subtle contextual clues and patterns that eluded human analysis for hundreds of years. This demonstrates the potential of AI in historical cryptography and complex problem-solving where traditional methods have failed.