Enigma message crack honours pioneering Polish codebreakers

Plus: The Reg chats to wartime Bombe operator Ruth Bourne

Enigma machine Shutterstock

The Bombe team at The National Museum Of Computing (TNMOC) has succeeded in breaking an Enigma-encrypted message in a live Poland-to-England demo.

The demonstration was described by TNMOC as a tribute to Polish cryptographers and wartime Bletchley Park staff.

The reconstructed Turing-Welchman Bombe at TNMOC in Bletchley Park found the settings and key needed to break an Enigma message. The techniques used were the same as those used by the WWII codebreakers.

Ruth Bourne, a wartime Bombe operator, was at hand to verify the authenticity of the exercise. The reconstructed Bombe was “clean and new” as opposed to the “battered and chipped” drums that Bourne remembers from her wartime service.

Nonetheless the authenticity was there. “I could operate it now and could plug it up,” Bourne told El Reg about the reconstructed machine. “It’s all very familiar.”

The TNMOC Bombe Team identified the decryption key of an English language Enigma-encrypted message sent from the World Computer Congress in Poznan, Poland during a live exercise today. The exercise took place alongside regular conference proceedings, which are being live-streamed, and featured presentations on cryptography, the Bombe and famous codebreaker Alan Turing.

The exercise on Friday demonstrated all the key phases of breaking an intercepted Enigma-encrypted message: from working out the wheel settings of machines used to send the message all the way through to the production of the plain text of encrypted messages. During WWII the German army changed the wheel settings and plug board settings every day. More advanced four- and five-wheel machines came into service as hostilities progressed.

Work by Polish mathematicians on early three-wheel versions of the Enigma laid the groundwork for the celebrated efforts of Turing and Gordon Welchman at Bletchley Park. It was the Poles who first broke the Enigma before the war began. Improved OpSec by Germany after hostilities broke out meant Wehrmacht telegram operators stopped sending the preamble to messages twice, so the crib needed for the device to work on Enigma-encrypted messages was no longer available.

The Bombe created at Bletchley Park was named in tribute to the less advanced Polish Bomba, a somewhat similar electro-mechanical device developed by Poland to crack German Army versions of the Enigma. The Turing-Welchman Bombe partially automated the decryption of Enigma-encrypted messages during WWII.

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The reconstructed Bombe was a labour of love put together by the team of enthusiast engineers using scavenged and spare parts that took more than eight years to build - longer than World War II itself - and completed in 2007, Bombe team member Paul Kellar told The Reg. The model contains 36 Enigma equivalents, each with three drums and wired to mimic the same enciphering process as real Enigma cipher machine motors.

The reconstructed Bombe was moved to The National Museum of Computing earlier this year following a successful crowdfunding effort and has been open to public viewing in a gallery since June. The museum also features a reconstruction of the wartime code-breaking Colossus, the forerunners of which were used to break the Lorenz cipher used by German High Command. ®

Bootnote

A new book by Alan Turing's nephew, Dermot Turing, called X, Y and Z: The Real Story of How Enigma Was Broken, covers the sometimes overlooked but crucial role of Polish codebreakers in cracking the Enigma. The author was a guest speaker at the World Computer Congress.




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