AI model GPT-6 Astra cracks 217-year-old Napoleon cipher

SentinelOne engineer Carter Church used OpenAI's GPT-6 Astra to break an unsolved cipher from a letter sent on Napoleon's orders in 1809, completing the task in six hours. The model worked from a low-resolution 1969 journal scan and a partial code table by historian Daniel Tant.

• The 1809 letter from Eugène de Beauharnais to Marshal Marmont held 1,300 signs across 155 symbols
• GPT-6 Astra cracked it in six hours from one prompt and one image
• The model found Tant's partial table covering a third of the cipher and decoded the rest
• Historians call the method a kind of Rosetta Stone for historical ciphers