GPT-6 Astra cracks 83-year-old Enigma message, says Bloomberg developer

The message itself is modest — a German soldier in 1941 reporting he was in Rosenow and asking for his march route. What makes the case notable is the method. Leffen and several specialized AI agents ran the search end to end: combing historical archives, comparing uncertain letters, building an Enigma simulator, writing cryptanalysis code, and cross-checking results. The Enigma offered roughly 159 quintillion possible daily settings, so brute force was never viable; the winning shortcut was a town name, "Rosenow," that also appeared in an already-decrypted message from the same day.

The work builds on prior cryptanalytic contributions by Frode Weierud, Geoff Sullivan, and Olaf Ostwald. Leffen points to the typos in the recovered text — "BTTE" instead of "BITTE" — as evidence of authenticity, since a fabricated answer would more likely be error-free.

Whether this holds up hinges on independent review of the published materials. As the article notes, the released packages verify the calculations but not the message's historical identity or that the solution is the only possible one — so experts will decide whether this becomes a template for AI-assisted cryptanalysis or a well-documented one-off.