Documents of Turing’s method of cracking Enigma found under roof

Notes for cracking the Nazis’ Enigma code appear to have been found while restoring a codebreaking facility in England’s Bletchley Park. The codebreakers used the papers as insulation material under the roof.

The documents appear to have been found as early as 2013 during the restoration of Hut 6, codenamed Station X, in Bletchley Park near the city of Milton Keynes, The Times reports. The paperwork had been frozen for conservation ever since and has now been restored for display in a month’s time. After the war, all the papers of the codebreakers were destroyed, but the now restored works were preserved because they were placed under the roof and in walls by the intelligence staff for insulation.

Among the papers are notes made in pencil, but there is also a Banbury Sheet, the only copy that still exists. With these sheets, the letters of the encrypted text were perforated, after which different sheets were placed over each other and slid. Then the holes that overlapped each other were counted.

A high result could be taken into account in a hypothesis about the settings of the rotors of an Enigma machine, which the Germans used in World War II to encrypt messages. The information could thus possibly speed up the cracking of intercepted messages that day. This technique was developed by Alan Turing and is also known as Banburismus. The name refers to Banbury, where the cards were printed.