Astra and Claude Opus 5 Decode Long-Unbroken Enigma Messages

On September 21, Jack Willis utilized Anthropic's Claude Opus 5 to decode an Enigma message that had remained unbroken since 2005. This achievement leaves only seven unbroken Enigma messages, with one containing known plaintext but an unbroken code. Frode Weierud, a retired electrical engineer and maintainer of the Crypto Cellar website, noted that GPT-6 Astra demonstrated capabilities akin to a professional cryptanalyst, achieving results in two days that would typically require weeks or months of human effort. Weierud had spent several weeks researching the Bundesarchiv files referenced by Astra. The successful decoding by both models highlights significant advancements in LLM applications for cryptanalysis, potentially altering approaches to historical code-breaking tasks.