Schlüsselgerät 41

The Schlüsselgerät 41 (shown here at the Science Museum in London) was developed from 1941 under the direction of the German cryptologist Fritz Menzer. It was intended to replace the Enigma as Germany’s next-generation cipher machine. However, by the end of the Second World War only 1000 to 1500 units had been manufactured – far too few to replace the Enigma, which was deployed in tens of thousands.

Because of its hand crank, the Schlüsselgerät 41 (shown here without its protective cover) became popularly known as the “Hitler Mill” (Hitlermühle in German).

Unlike the Enigma, the Schlüsselgerät 41 did not rely on wired rotors. Instead, it used pin wheels with movable pins, a cryptographic principle that Fritz Menzer adopted from the cipher machines developed by Boris Hagelin.

Source: Niemann

Shown here is the bar basket, a characteristic feature of Hagelin’s C machines. The Schlüsselgerät 41 adopted this feature.

Source: Mattey

The Schlüsselgerät was also available in a version with a numeric keypad.

Source: Mattey

This specimen, too, on display at the Typewriter Museum Partschins in South Tyrol, features a numeric keypad.

The Schlüsselgerät 41 (shown here at the Charlotte Crypto Symposium 2026) was considerably more secure than the Enigma. With the cryptanalytic techniques and computing resources available during the Second World War, it was considered beyond practical attack.

To the best of current knowledge, it has not yet been thoroughly investigated whether modern cryptanalytic methods and computing power could break the system efficiently.

Source: Mattey

Today, the Schlüsselgerät 41 is a highly sought-after collector’s item. The example shown here is on display at the Typewriter Museum Partschins in South Tyrol.

Three Schlüsselgerät 41 machines were exhibited at the Charlotte Cryptologic Symposium in 2012 – an exceptionally rare sight, given the small number of surviving examples.

It is estimated that around 50 Schlüsselgerät 41 machines survive today. Many of them are heavily damaged, such as this example at the Typewriter Museum Partschins in South Tyrol.