A previously unsolved 1941 German Army Enigma radio message has been decrypted for the first time after OpenAI’s GPT-6 Astra autonomously cracked the cipher in roughly ten hours of model time[2][6][13]. Carter Leffen, a product development coach at Bloomberg, instructed the system only to look for unsolved Enigma traffic and attempt a break; the model independently selected the intercept catalogued as message 172 with indicator MVUEH from the Crypto Cellar Research archive and proceeded without further human guidance[6][8][9].
According to accounts of the project, GPT-6 Astra analyzed the set of unbroken messages and quickly hypothesized that the plaintext for message 173, tagged SIPVX, might be related to the MVUEH traffic, suggesting a shared context or location[8][9]. It identified the repeated place name ROSENOW ROSENOW from already-decrypted messages as a promising crib, then generated its own Python and C++ implementations of an Enigma simulator and virtual Bombe to search keyspace, ultimately running on the order of tens of millions of key checks before converging on a solution[3][8][11]. Researchers at Crypto Cellar report that the AI handled the entire workflow—from corpus triage and crib selection to code synthesis and key testing—without being given specialized cryptanalytic algorithms in advance[8][9].
The recovered plaintext is routine operational traffic, but its brevity and errors are exactly what had stymied human codebreakers for decades[2][13]. Multiple write-ups describe the 82-character Wehrmacht message, sent on July 10, 1941 during the German advance into the Soviet Union, as reading in essence: Please specify route of march. I am in Rosenow, Rosenow. Immediate reply by radio.[2][13][14] Cryptographers note that the short length, operator typos, and lack of obvious standard phrases made traditional crib-based attacks difficult, even with knowledge of Enigma’s design flaws, leaving the intercept marked as “unsolved” in archives for more than 80 years[2][8][15].
Technical details published after the break show that the solution fits cleanly within the German Army’s July 1941 keying procedures and Enigma configuration, including rotor selection, ring settings and plugboard wiring reconstructed from historical records[11][15]. Enigma’s architectural weakness—that no letter ever encrypts to itself because of the reflector wiring—combined with the repeated place name crib allowed GPT-6 Astra to prune impossible positions and dramatically reduce the search space, a strategy long used by human codebreakers but here rediscovered and operationalized by an AI agent[8][13][14]. Crypto Cellar has since updated its July 1941 key listings to include the recovered settings for MVUEH, effectively closing a long-standing gap in the historical record[8][15].
Beyond its historical interest, the episode is being watched closely by security practitioners as a concrete demonstration of how large, tool-using AI systems can autonomously orchestrate multi-step cryptanalytic campaigns[6][11]. Case studies describe GPT-6 Astra’s “extra high” variant spinning up parallel specialist agents, searching historical archives, synthesizing and debugging code, running competing experiments, and cross-checking candidate keys against plausibility criteria before presenting a final plaintext and key schedule[6][11][13]. While Enigma is a broken and obsolete cipher, the workflow on display—automated reconnaissance, environment modeling, and iterative attack refinement—maps closely onto modern offensive security tasks such as protocol reverse engineering and exploit development.
Cryptographers caution that the successful attack on an already-insecure World War II cipher does not imply that contemporary algorithms like AES or modern public-key schemes are suddenly vulnerable, but the MVUEH break underscores how quickly AI capabilities are moving toward automating complex analytical work once reserved for human specialists. Researchers at Crypto Cellar and security commentators such as Bruce Schneier say they are still combing through GPT-6 Astra’s logs to understand precisely how it chose its strategy and managed the search, and intend to publish further technical analysis of the run[8][9][13]. For defenders, the story is a reminder that the same autonomous reasoning and tooling that can resurrect a forgotten Enigma intercept can also be directed toward bug hunting and protocol abuse, reinforcing the need to harden systems, monitor AI-assisted threat activity, and invest in equally capable defensive automation.
References
- GPT-6 Astra cracks a 1941 Enigma message that had …
- OpenAI’s GPT-6 Astra Cracked a Nazi Enigma Message in 10 Hours: Is Bitcoin Next?
- OpenAI’s GPT-6 Astra decrypts a Nazi radio message in ten …
- The MVUEH Break – Crypto Cellar Research
- history of cryptography Archives – Schneier on Security –
- The MVUEH Enigma break, read as a gate-design case ¶
- Singularity Moments
- How GPT-6 Astra Solved Historical Ciphers
- Frode Weierud’s CryptoCellar | Enigma Keys – July 1941
