Artificial intelligence deciphers 200-year-old Napoleonic-era encrypted letter

Artificial intelligence deciphered a letter written by the order of Napoleon Bonaparte for the first time in more than 200 years.

Carter Church, an engineer working at the cyber security company SentinelOne, wrote on social media that OpenAI's GPT-6 Astra model decrypted an encrypted letter dated 1809 and that this letter was sent to French General Auguste de Marmont.

This document was not a letter written directly by Napoleon, but an encrypted troop instruction prepared at the headquarters of the Italian Governor-General Eugène de Beauharnais and transmitted to the French General Auguste de Marmont by Napoleon's order.

According to Church, the artificial intelligence model converted the image into text in about six hours to crack the password.

NO RESEARCHER HAS BEEN ABLE TO SOLVE IT FOR YEARS

"Astra divided the 1202 x 1836 plate into lines, read the signs, determined which of the 175 hand-drawn signs were the same sign written twice, and only then began to decipher," Church said in his blog post.

Numerous researchers have attempted to reconstruct the contents of the document over the decades, but none have published a full analysis.

The text laid out the positions of the Bavarian, Polish and French forces.

While Europe was on the brink of war in 1809, Austria was preparing to fight with France, and a large part of the French forces were still held in Spain. Commanding French troops in Dalmatia, Marmont risked being isolated if Austria attacked.

On 16 March, Napoleon ordered Eugène to report to Marmont the positions of the main French and allied forces, specifically stating that the message should be “written in code” and carried by a trusted officer.

The document states, "The Russians marched against Austria and the Friuli army consists of eighty thousand people today."

On the other hand, some of the statements in the encrypted message were as follows;

"Add the Dalmatian corps and you will see that Austria will be attacked from all directions at once, even without counting the reserves organized everywhere behind. As a result, she is rapidly moving towards her own destruction. When you receive the marching orders, you must not fear that there are a few troops or a rabble gathering."

APPROVAL FROM JAPANESE RESEARCHER

Using deciphered troop numbers, officer ranks, and unit locations, Church dated the document to late March 1809, approximately two weeks before Austrian forces launched their offensive.

On September 18, Church published his complete research record, including transcription, password tables, and scripts that enabled others to replicate this result.

According to Church, Tokyo-based researcher Satoshi Tomokiyo, who runs the Cryptiana site, reviewed the solution and marked the entry as “solved.”