GPT-6 Astra cracks 217-year-old Napoleonic military cipher
Astra analyzed a 1,300-symbol ciphertext from 1809, reconstructed the key and solved it with simulated annealing; a cryptographer has confirmed the historical cipher as solved.
GPT-6 Astra cracked a 217-year-old Napoleonic military cipher. The encrypted letter dates to March 1809 and was sent to Napoleon’s marshal Auguste de Marmont, shortly before Austria invaded France’s sphere of influence. Astra reportedly analyzed the 1,300-symbol ciphertext, reconstructed the missing key from historical material and used simulated annealing to solve it. The decoded message contains military intelligence on troop positions and Austrian movements. Cryptographer Satoshi Tomokiyo reviewed the solution and marked the previously unsolved cipher as solved, although five symbols remain uncertain.