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Enigma Code-Breaking Machine Rebuilt at Cambridge

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Polish cyclometer replica

The 1930s Polish cyclometer replica is currently on display at King's College, Cambridge.

University of Cambridge alumnus Hal Evans has built a fully-functioning replica of a 1930s Polish cyclometer — an electromechanical cryptologic device that was designed to assist in the decryption of German Enigma ciphertext.

Work on the hardware-based replica began in 2018. The aim was to investigate further into cryptologist Marian Rejewski's cyclometer — an early forerunner to Cambridge University mathematician Alan Turing's machine, known as the Bombe, which was used to crack the German Enigma code during the Second World War.

Evans says the cyclometer was the very first machine used to assist the decryption effort. To his knowledge, the replica is the first fully-functioning hardware-based electromechanical cyclometer to exist since before World War II. The original machines were destroyed in 1939 to prevent them from falling into the hands of German invaders.

Researching Rejewski and his colleagues' work showed "quite how advanced the Poles were in their understanding of Enigma compared to the British in 1939," Evans says. "The Poles were, in fact, the first to crack the Enigma code prior to the start of the War . . . and laid the foundations for the Allies' later success at Bletchley Park."

From University of Cambridge
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