Editing Enigma machine (section)

=== Electrical pathway ===
[[File:Enigma wiring kleur.svg|thumb|left|upright=1.3|Enigma wiring diagram with arrows and the numbers 1 to 9 showing how current flows from key depression to a lamp being lit. The ''A'' key is encoded to the ''D'' lamp. D yields A, but A never yields A; this property was due to a patented feature unique to the Enigmas, and could be exploited by cryptanalysts in some situations.]]
An electrical pathway is a route for current to travel. By manipulating this phenomenon the Enigma machine was able to scramble messages.<ref name="Enigma History"/> The mechanical parts act by forming a varying [[electrical network|electrical circuit]]. When a key is pressed, one or more rotors rotate on the spindle. On the sides of the rotors are a series of electrical contacts that, after rotation, line up with contacts on the other rotors or fixed wiring on either end of the spindle. When the rotors are properly aligned, each key on the keyboard is connected to a unique electrical pathway through the series of contacts and internal wiring. Current, typically from a battery, flows through the pressed key, into the newly configured set of circuits and back out again, ultimately lighting one display [[Electric light|lamp]], which shows the output letter. For example, when encrypting a message starting ''ANX...'', the operator would first press the ''A'' key, and the ''Z'' lamp might light, so ''Z'' would be the first letter of the [[ciphertext]]. The operator would next press ''N'', and then ''X'' in the same fashion, and so on.

[[File:Enigma-action.svg|thumb|upright|The scrambling action of Enigma's rotors is shown for two consecutive letters with the right-hand rotor moving one position between them.]]
Current flows from the battery (1) through a depressed bi-directional keyboard switch (2) to the plugboard (3). Next, it passes through the (unused in this instance, so shown closed) plug "A" (3) via the entry wheel (4), through the wiring of the three (Wehrmacht Enigma) or four (''[[Kriegsmarine]]'' M4 and ''Abwehr'' variants) installed rotors (5), and enters the reflector (6). The reflector returns the current, via an entirely different path, back through the rotors (5) and entry wheel (4), proceeding through plug "S" (7) connected with a cable (8) to plug "D", and another bi-directional switch (9) to light the appropriate lamp.<ref name="Rijmenants">Rijmenants, Dirk; [https://www.ciphermachinesandcryptology.com/en/enigmatech.htm Technical details of the Enigma machine] Cipher Machines & Cryptology</ref>

The repeated changes of electrical path through an Enigma scrambler implement a [[polyalphabetic cipher|polyalphabetic substitution cipher]] that provides Enigma's security. The diagram on the right shows how the electrical pathway changes with each key depression, which causes rotation of at least the right-hand rotor. Current passes into the set of rotors, into and back out of the reflector, and out through the rotors again. The greyed-out lines are other possible paths within each rotor; these are hard-wired from one side of each rotor to the other. The letter ''A'' encrypts differently with consecutive key presses, first to ''G'', and then to ''C''. This is because the right-hand rotor steps (rotates one position) on each key press, sending the signal on a completely different route. Eventually other rotors step with a key press.