The AI model Claude Fable 5.1 has successfully deciphered the "Cyphral Distich," a code that had remained unsolved for over 370 years, found within the works of the 17-century writer Sir Thomas Arcat.
AI "Claude Fable 5.1" Deciphers 370-Year-Old Unsolved Code, Identifying Content Supporting Charles 2
This article is a translation. Read the Japanese original
This code consists of 2 lines of text located at the end of Arcat's work "Logopandecteision," with each line containing 32 numbers. According to verification by AI researcher Gebby Jaf and others, it was reported that Claude Fable 5.1 succeeded in deciphering the code after 44 minutes of processing and consuming 170,000 6,000 tokens.
The AI focused on the fact that the code was placed immediately following the phrase "32 Proquiritations (32 wishes)" and the notation that the book itself held the key to deciphering it. As a result, it discovered the decryption rule: "For the i-th number (n) in the ciphertext, take the first letter of the n-th word appearing in the i-th Proquiritation."
The deciphered message read: "O God, protect King Charles 2, and establish him as the supreme ruler of this land." This was a message supporting the restoration of the monarchy of that era, consistent with the historical fact that Arcat was a fervent Royalist.
Jaf analyzed this achievement, stating that rather than a special analytical capability, the key was the AI's "persistence" in continuing the search until it found the rules.
Sources
- Claude Fable 5.1が370年前の未解読暗号「Cyphral Distich」を1日足らずで解読 （GIGAZINE、2026-09-17）
- Geby Jaff氏のブログ