The Enigma Machine

[MelvinS4_]

This is very doable, however it would be a fairly big task. I would construct the rotors from a decoder, a counter and an adder. The decoder contains the cross-wiring inside the rotors, and the adder and counter combination represents the rotation of the rotor. You add the numerical value of the letter you want to encrypt to the value of the counter and then run it through the decoder.

I also believe this has already been done, but I don't have any reference to it.