GPT-6 Astra Breaks a German Enigma Message Unsolved Since 2005

Summary

Crypto Cellar Research reports that GPT-6 Astra solved MVUEH, a German Army Enigma message sent on 10 July 1941 and unsolved since 2005. The report says Carter Leffer asked the model to examine unbroken messages, after which it selected message No. 172 and suspected a relationship with the already solved No. 173, SIPVX. GPT-6 Astra reportedly focused on the repeated place name “ROSENOW ROSENOW” as a crib, then developed Python and C++ software for an Enigma simulator and Bombe before finding the correct key and plaintext. The recovered key differs from the daily key used for other messages that day: it uses wheel order 253 rather than 512, and the plaintext is nearly identical to SIPVX. MVUEH contains 82 letters, compared with 94 for SIPVX; the report attributes the difference to a transcription or enciphering error in “Bitte,” producing “Btte,” and to a repeated sender signature in SIPVX. The analysis also exposed several ciphertext transcription errors and a rare turnover of the Enigma’s left-hand wheel at letter 72, both of which may have impeded earlier attempts. The author says GPT-6 Astra also identified relevant Bundesarchiv file references while investigating the surrounding message collections, although the original No. 172 image had not been located. Logs were still being analyzed, so the exact sequence of the model’s work and its archive access remained uncertain. The report presents the result as an autonomous AI cryptanalysis achievement, while the historical and technical claims come from the site’s account of the break.