History’s long-secret codes are being cracked by amateurs using AI
Nature, Published online: 16 October 2026; doi:10.1038/d41586-026-03338-y Cryptographers’ inboxes are being flooded with requests to validate cipher solutions.
Amateur codebreakers, using artificial intelligence tools like GPT-6 Astra, are cracking long-secret codes that had remained undeciphered for decades. Carter Leffen, who has no cryptography background, asked the AI model to decode a message from the German army that had been encrypted for 85 years. When he woke up the next morning, the AI had solved the code.
Similar efforts are being conducted by other non-experts, who use LLMs to rapidly deploy decryption algorithms and search the internet for additional historical documents or information. While cryptography specialists are thrilled with this surge of interest in codebreaking, they are also overwhelmed by a flood of requests to validate AI solutions, many of which can be incorrect.
In another instance, Carter Church, a staff engineer at SentinelOne, used GPT-6 Astra to decode a cipher sent by an Italian official to Napoleon's general in 1809. GPT-6 Astra found a partial key and used simulated annealing, an iterative decoding strategy, to crack the code. The AI significantly reduced the time and effort required to solve the cipher, which turned out to describe troop locations.
Written by urgent.news from Nature's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
