Researchers at Crypto Cellar report that ChatGPT-6 Astra has decrypted an Enigma-encoded German Army message from 1941, known as MVUEH. The 82-letter ciphertext was sent to the SS-Totenkopf Division on July 10, 1941, and had been shared with the cryptanalysis community online in 2005 without being solved.
According to the researchers, Astra picked the message itself from a list of unbroken Enigma transmissions on the Crypto Cellar website. It hypothesized that the repeated place name "ROSENOW ROSENOW" was a probable plaintext clue, then wrote its own Python and C++ code to simulate an Enigma machine and a Bombe. The decrypted text reads as a request for the route of march, with the sender reporting their location in Rosenow and asking for an immediate radio reply.
The Crypto Cellar team notes that what Astra accomplished in two days would take a human researcher weeks or months, and that the AI did it "entirely on its own." They are still reviewing logs to understand how it worked so quickly. The feat follows a similar success last week, when Astra cracked a 108-year-old WWI ADFGVX cipher, suggesting a growing pattern of autonomous codebreaking by large language models.