OpenAI’s GPT‑6 Astra Deciphers Long‑Unsolved Enigma Message from 1941

Background of the MVUEH Enigma Message

On 15 September 2026 Carter Leffer contacted the author to request validation of a break of the German Army Enigma message MVUEH, transmitted on 10 July 1941.

The message was sent by a radio station with the tactical callsign 2ny and received by the SS‑Totenkopf Quartiermeister station Ib at 17:30, where it was logged as number 172 in the July 1941 incoming‑message register.

Since 2005 the ciphertext of MVUEH had resisted every cryptanalytic attempt, making it a benchmark for Enigma research.

In June 2017 Alex Shovkoplyas succeeded in breaking another unbroken message from the same day, number 173 titled SIPVX, but the recovered key differed slightly from the daily key used for other messages on 10 July 1941.

Specifically, SIPVX used the same wheel order 512 as the daily key, while its plugboard connections and ring settings were altered.

Despite this progress, the SIPVX key did not enable a solution for MVUEH.

GPT‑6 Astra’s Autonomous Break

Carter Leffer instructed GPT‑6 Astra only to examine the list of unbroken Enigma messages published on the Crypto Cellar Research website.

The model independently selected MVUEH (Nr.  172) as the most promising target and quickly hypothesised a link to the plaintext of SIPVX (Nr.

173).

GPT‑6 Astra identified the repeated place name “ROSENOW ROSENOW” as a crib and built the necessary Python and C++ software for an Enigma simulator and an Enigma Bombe.

Using the ROSENOW crib, the system launched a thorough search that ultimately produced the correct key and plaintext for MVUEH.

The recovered key proved entirely different from other keys of 10 July 1941, employing wheel order 253 instead of the usual 512.

The plaintext of MVUEH is almost identical to that of SIPVX, differing only by twelve letters because the word “Bitte” was mis‑enciphered as “Btte” and the sender’s signature “Waschbusch” appears twice in SIPVX.

Analysis of the break revealed transcription errors in the original ciphertext and a rare turnover of the Enigma’s left‑hand wheel at the 72nd character, a factor that likely complicated earlier attempts.

The discovery that GPT‑6 Astra achieved the solution without human‑directed cryptanalytic steps is notable for demonstrating autonomous problem solving in a historically complex domain.

Implications and Ongoing Analysis

Researchers continue to examine GPT‑6 Astra’s execution logs to understand the exact sequence of heuristics and computational strategies it employed.

In July 2026 the author announced on the 1941 Message List webpage that the German Bundesarchiv had revealed additional collections of radio messages from the SS‑Totenkopf Division’s logistics command.

Many of these newly uncovered messages correspond to those already listed, while others appear related and are now marked with the indicator NF (Nachschubführer) in bold blue entries.

It appears that GPT‑6 Astra discovered the Bundesarchiv note about the message collections during its analysis, highlighting the model’s ability to surface relevant archival information.

The successful autonomous break opens the possibility of revisiting other long‑standing unsolved cryptograms with advanced language models.

Historians may gain new insights into World‑War‑II communications, logistics, and operational decisions as more messages become readable.

At the same time, the episode raises questions about the reproducibility of AI‑driven cryptanalysis and the need for transparent logging of model reasoning.

Future work will likely involve integrating GPT‑6 Astra’s methods with traditional cryptanalytic expertise to accelerate the decoding of remaining Enigma archives.

Why This Matters: The autonomous break demonstrates how advanced language models can contribute to historical cryptanalysis, opening new avenues for research.