Researcher Carter Leffen used the GPT-6 Astra model to decrypt a German military radio message from July 10, 1941. The message, identified as MVUEH, remained unsolved in the CryptoCellar archive since 2005 and contains 82 encrypted characters.
The process took place between September 14 and 15. Astra and several AI agents autonomously searched archives, compared ambiguous characters, and wrote cryptanalysis code in Python and C++. The system tested approximately 4.29 billion combinations of crib positions and rotor settings.
The team utilized a previously decrypted message from the same day, SIPVX, as a reference. By assuming the sequence ROSENOWROSENOW was present in the MVUEH message, they narrowed down the search parameters. Researchers identified 12 points in the original document where handwritten letters were unclear.
Following the identification of a candidate key, the system verified approximately 14.8 million physical keys. The final parameters included rotor order II-V-III, ring settings H-M-F, initial positions R-W-D, and ten plugboard connections. Two independent Enigma simulations confirmed the result.
The decrypted text indicates the sender was located in Rosenow and requested immediate radio instructions regarding their route. Enigma expert Frode Weierud verified the findings, noting that the key differs from other known keys from that date. The authors clarified that this was a specific decryption task rather than a general breach of the Enigma cipher.
