Like other rotor machines, the Enigma machine is a combination of mechanical and electrical subsystems.

Several inventors had similar ideas about the same time, and rotor machines were patented four times in 1919 .

A rotor machine, the device used eight rotors each with a tyre ring and an insert.

Friedman realized that the new rotor machines would be important, and devoted some time to analysing Hebern's design.

Friedman used his understanding of rotor machines to develop several that were immune to his own attacks.

The system is a rotor machine, and would appear to have used 10 rotors.

They were large, two rotor machines, painted all black and wearing no markings.

Friedman went on to design a much more secure and complex rotor machine for the US Army.

So while such a single rotor machine is certainly easy to use, it's no more secure than any other partial polyalphabetic cipher system.

The concept of a rotor machine occurred to a number of inventors independently at a similar time.