Mar 6, 2017 | By Benedict

Engineers from the UK’s Government Communications Centre (HMGCC) are using 3D printing to recreate the Lorenz SZ42, an “unbreakable” cipher machine used by Hitler and the German Army during World War II. Only four of the machines still exist.

Lorenz SZ42, Hitler's "unbreakable" cipher machine

During the Second World War, various versions of the Lorenz cipher were used by the German Army to encrypt strategic communications. These machines, each of which contained 12 wheels with a different number of pins, were attached to standard teleprinters in order to turn readable German text into code. A duplicate Lorenz cipher fitted to a teleprinter at the receiving end would then turn the encrypted message back into German.

Originally considered unbreakable by the Germans, the Lorenz cipher was eventually cracked by British codebreakers at Bletchley Park, the UK’s central codebreaking site, in Buckinghamshire. Because the Lorenz ciphers were used by the Germans to encode extremely important strategic information, Britain’s decrypting of the machine’s messages was integral to the eventual Allied victory.

Around 200 units of the Lorenz SZ42, one of four versions of the machine, were used during the war, but only four survive. One of those four SZ42s, a machine that was used by the German Army in Norway, was recently given to the UK’s National Museum of Computing at Bletchley Park (TNMOC) on long-term loan from the Norwegian Armed Forces Museum. There, the machine will be receiving some important maintenance work. Because the cipher is missing some components, including a motor, engineers from HMGCC are using 3D scanning and 3D printing technology to rebuild it.

Lorenz teleprinter, wheel setting guide, and SZ42 cipher

UK veterans Betty O'Connell and Irene Dixon operated the Colossus to break Lorenz code during WWII

Lorenz SZ42 cipher in the USA with motor (top) intact

The exciting project will involve two key stages: first, using 3D scanning equipment to reverse engineer an existing Lorenz motor from a different machine, and second, 3D printing a replica of that motor which can then be fitted to the recently borrowed SZ42. “The HMGCC team will take three-dimensional images of an existing Lorenz motor and then reconstruct it using 3D printing techniques,” explained John Whetter of TNMOC. “Externally, the motor will be almost indistinguishable from an original.”

The Lorenz machine receiving 3D printing maintenance was seized by the Norwegian secret services following the conclusion of the war. Soon, with a 3D printed motor fitted to it, the machine will be used by staff at TNMOC to demonstrate how code from the Lorenz was eventually deciphered by the British codebreaking machine Colossus, which was designed by research telephone engineer Tommy Flowers and mathematician Max Newman, using contributions from cryptanalyst Alan Turing.

Wheels of the Lorenz SZ42

Ablesetafel 40 or Spruchtafel, used to determine Lorenz wheel settings

Lorenz teleprinters like these were linked to the ciphers

A HMGCC spokesman commented: “The wartime work at Bletchley Park, including breaking the Lorenz cipher, was instrumental in the birth of modern computing and the development of what we now call cyber security. HMGCC looks forward to its young apprentices reconstructing this machine in support of TNMOC's wider work to explain why Bletchley Park's legacy still matters today.”

According to TNMOC, the reconstructed Lorenz SZ42 cipher containing the 3D printed motor could be ready by summer 2017.



Posted in 3D Printing Application



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