Enigma

A solution was already at hand to the Nazi Military and had been since 1918 when a machine called Enigma was invented by Arthur Scherbius to allow secure communications for the Financial Institutions. The banks never really got on with it but the Nazi Military pounced on Enigma as the solution to their communication problems for their fast moving war.

Enigma is a cypher machine.

Enigma was a unbelievably complex machine and thought to be absolutely secure by the Nazis. It consisted of 4 main parts.

1). Set of Rotors   2). Indicator Lights   3). Keyboard   4). Plug board

A lot of the complexity in the Enigma machine comes down to the interaction of the rotors. Each rotor is a tiny wiring loom with 26 inputs and 26 outputs, one for each letter. So an input on the 'A' channel might be an output of 'R'.

When a letter key is pressed a current passes through the three rotors on their wired paths, hits a bounce plate and then comes back through the rotors to light an indicator lamp.

Then the left rotor clicks on a position, on a full rotation of a rotor, the next rotor clicks on a position.

Each rotor has it's own 'random' wiring.