Two frontier AI models helped decode German Army Enigma messages from July 1941 that had remained unsolved in the public Crypto Cellar collection since 2005. The first break, of message MVUEH, used OpenAI's GPT-6 Astra. Days later, Anthropic's Claude Opus 5 was used on another unsolved message.
The story received fresh coverage on Saturday, September 26, 2026, from Tom's Hardware, after TechCrunch on Friday and technical validation by the archive's curator.
What happened
On September 15, developer Carter Leffen asked GPT-6 Astra to try unbroken Enigma messages on Crypto Cellar's research page. According to Frode Weierud, the model picked MVUEH, an 82-letter message dated July 10, 1941, sent to an SS-Totenkopf radio station.
Astra linked it to the already solved neighboring message SIPVX, used the repeated place name ROSENOW ROSENOW as a crib, and wrote Enigma simulator and Bombe-style software in Python and C++. Weierud validated the key and plaintext. The text asks for a march route and an immediate radio reply.
On September 21, cybersecurity executive Jack Willis told Weierud he had used Claude Opus 5 to break another message, FMNGI, with more human guidance, including a known officer signature.
Why it matters
This is three-rotor Army traffic, not four-rotor naval Enigma. The ciphertext includes an encoding error (Btte instead of Bitte) and a rotor order that differs from other keys recorded that day. Even so, it is a concrete long-horizon agent case: archival research, a hypothesis, tool generation and a constrained search.
Weierud wrote that what Astra did in two days would take a human researcher weeks or months. He also noted uncertainty about log mentions of a private collection and Bundesarchiv files. It is not clear whether the model actually accessed those holdings.
What is still open
Emphasis differs. Weierud describes the MVUEH break as done entirely on its own from a generic prompt. Later write-ups note that the solver's own case study frames a researcher-led investigation. The plaintext and key, however, have been independently checked and are reproducible.
Weierud says seven Enigma messages remain unsolved in the collection, plus one with known plaintext and an unbroken cipher.
Sources
- The MVUEH Break — Crypto Cellar
- The FMNGI Break — Crypto Cellar
- TechCrunch
- Tom's Hardware
- Schneier on Security
Transparency: This content was created, edited or reviewed with the aid of artificial intelligence. Information was cross-checked with public posts on X and sources available on the internet. Consult the original sources for the full context.
Por GeekikiBot