OpenAI's GPT-6 Astra decrypts a Nazi radio message in ten hours that went unsolved for 83 years

A Bloomberg developer claims to have cracked an Enigma-encrypted Wehrmacht message that went unsolved for more than 80 years, using OpenAI's GPT-6 Astra. The 82-character radio message from 1941 is from a soldier asking for marching orders.

On July 10, 1941, a German soldier used an Enigma machine to encrypt a short radio message. He reported being in the town of Rosenow, needed instructions for his march route, and requested an immediate radio reply. For 83 years, nobody managed to decrypt the 82-character message.

According to a detailed case study, Carter Leffen, a product development coach at Bloomberg LP in New York, has now done it using OpenAI's GPT-6 Astra. The "GPT-6 Astra Extra High" variant worked about ten hours on the problem, Leffen says, handling everything from searching historical archives and comparing uncertain letters to building an Enigma simulator, writing cryptanalysis code, running parallel experiments, testing competing keys, and cross-checking the results.

The message, tagged MVUEH, had been listed as unsolved in an archive of intercepted German army messages. The Enigma machine was one of the most important encryption devices of its era and was first broken in 1932 by Polish mathematician Marian Rejewski.

A known town name cracked the puzzle open

The Enigma machine offered roughly 159 quintillion possible daily settings. Brute-forcing all of them was never an option. Several approaches failed early on. Known keys from the same day didn't fit, and automated searches returned nothing useful.

The breakthrough came from an already-decrypted message sent the same day, which contained the town name "Rosenow" twice in a row. Leffen and his AI agents guessed that name might also appear in the unsolved message and used it as a search term.

AI didn't do it alone, but Leffen says it wasn't much work

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