Tunny

German code device

Also known as: Schlüsselzusatz SZ40

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Last updated

July 19, 2026

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The Tunny machine was a sophisticated German cipher device used during World War II. It was a 12-wheel machine produced by the Lorenz company, requiring only one operator. Unlike the Enigma machine, Tunny did not use Morse Code and its encrypted output went directly to a radio transmitter. The British code-breaking operation at Bletchley Park, known as Ultra, successfully decrypted Tunny messages starting in July 1942. These decrypted messages provided crucial intelligence on German strategy, particularly regarding preparations for the Allied invasion of Normandy. Breaking Tunny messages led to the development of the world's first programmable electronic computer, Colossus, to handle the high volume of encrypted traffic.1

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Colossus
…that the British code-named “Tunny.” Tunny was the Schlüsselzusatz (SZ) cipher attachment, manufactured by Berlin engineering company C. Lorenz AG. Tunny sent its messages in binary code—packets of zeroes and ones resembling the binary code used inside present-day computers.
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…that the British code-named “Tunny.” Tunny was the Schlüsselzusatz (SZ) cipher attachment, manufactured by Berlin engineering company C. Lorenz AG. Tunny sent its messages in binary code—packets of zeroes and ones resembling the binary code used inside present-day computers.
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Ultra
Tunny
In 1940 the German Lorenz company produced a state-of-the-art 12-wheel cipher machine: the Schlüsselzusatz SZ40, code-named Tunny by the British. Only one operator was necessary—unlike Enigma, which typically involved three (a typist, a transcriber, and a radio operator). The Tunny operator simply typed in…
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In 1940 the German Lorenz company produced a state-of-the-art 12-wheel cipher machine: the Schlüsselzusatz SZ40, code-named Tunny by the British. Only one operator was necessary—unlike Enigma, which typically involved three (a typist, a transcriber, and a radio operator). The Tunny operator simply typed in…
Read More