GPT-6 Astra Successfully Deciphers Unsolved ADFGVX Cipher from World War I

Cases have been reported where the GPT-6 Astra model deciphered messages that had remained unsolved for decades among the ADFGVX ciphers used by Germany during World War I.

Decryption Process and Results

• Target Message: An unsolved ciphertext transmitted on November 27, 1918, which was included in Scienceblogs.de's list of '50 Unsolved Ciphers'.
• Recovered Content: Military operational information stating that "the British cruiser HMS Canterbury has arrived in Sevastopol, followed by the Allied fleet."
• Key Used: The model inferred and used the encryption key word 'TRUPPENVERSCHIEBUNG'.
• Verification: Original logs of HMS Canterbury matching the decrypted content were confirmed, proving the accuracy of the decryption.

Technical Background and Significance

• ADFGVX Method: A method that substitutes characters with two-letter combinations using a 6x6 grid, where the grid contents change according to the key word.
• Reason for Being Unsolved: Although records indicate that the key was used starting December 9, 1918, the actual message was transmitted in November, prior to that date, suggesting it remained undeciphered due to a key mismatch.
• Significance: By resolving the key mismatch issue that previous cryptographers had overlooked through reasoning, the LLM demonstrated its capabilities in complex pattern recognition and logical reasoning.