OpenAI's Astra model decodes Enigma message unsolved since 2005

Developer Carter Leffen asked OpenAI's newest model, Astra, to search a database of Enigma messages for an unbroken message and decode it. The model carried out its own archival research, found contextual clues, built a simulator of the Enigma machine, and recovered the plaintext of a message that had remained unsolved since 2005. Leffen also used Astra to build an interactive website explaining the problem.

Enigma was an encryption device used by Nazi Germany during World War II. A handful of archival messages remain unbroken, often because of mistranscription or errors by the original encoders. Frode Weierud, a retired electrical engineer who maintains the cryptology resource site Crypto Cellar, validated Leffen's solution in September 2026. He said the result left him in 'awe' and described the model as behaving 'like a very professional cryptanalyst and archive researcher,' noting that what it achieved in two days would take a human researcher weeks or even months.

Weierud said Astra's logs included discussion of archived messages in a 'private collection' that are not hosted by him, and he is still unsure whether the model accessed them or found them elsewhere. He also noted that only seven unbroken Enigma messages remain, along with one message whose plaintext is known but whose code is still unbroken.