Two cryptographers claim that, using large models from OpenAI and Anthropic, they have decrypted two long-unsolved Enigma ciphertexts. These ciphertexts originated from the Enigma machines used by Germany during World War II, and some archival information had remained unrecovered until now.
Astra first decrypts an old ciphertext.
Developer Carter Leffen said he tasked OpenAI’s latest model, Astra, with searching an Enigma ciphertext database for an unsolved message and attempting to decrypt it. Astra then completed steps including archival retrieval, identifying contextual clues, and building an Enigma simulator, ultimately recovering the plaintext.
The report mentions that this message has puzzled researchers since 2005. Leffen also used Astra to create an interactive website demonstrating the entire decryption process.
Validators claim efficiency far exceeds manual processes.
Frode Weierud, who maintains the cryptography website Crypto Cellar, subsequently verified the result. He has long compiled Enigma-related documents and message databases and said that this solution surprised him.
Weierud noted that Astra’s operational logs also referenced certain “private collections” not hosted on its website. He is still uncertain whether the model actually accessed these materials, speculating that the content may have come from publicly uploaded sources by other researchers or from publicly available German government archives.
Claude Opus 5 breaks another record
On September 21, another cryptographer, Jack Willis, contacted Weierud, stating that he had deciphered another encrypted message using Anthropic’s Claude Opus 5.
Compared to the Astra case, Willis provided more guidance to the model during the process. Ultimately, Claude used the known clue—the signature of a specific officer’s name—to reconstruct the message.
According to Weierud’s statistics, seven Enigma ciphertexts remain unbroken, and one message, although its plaintext is known, has not yet been fully deciphered in terms of its cryptographic process.