▸ Signal Path
Each keypress: Plugboard → Right Rotor → Middle Rotor → Left Rotor → Reflector → Left Rotor (back) → Middle Rotor (back) → Right Rotor (back) → Plugboard → Lamp.
▸ Double-Stepping Anomaly
A mechanical quirk: when the middle rotor is at its turnover notch, it advances itself AND the left rotor — so the middle rotor can step twice consecutively.
▸ Self-Reciprocal Property
If A enciphers to Z, then Z enciphers to A (same settings). The reflector guarantees this. Crucially: a letter NEVER encrypts to itself.
▸ Ring Settings (Ringstellung)
Offsets the internal wiring relative to the rotor's external alphabet ring. Adds a second layer beyond starting position.
▸ Plugboard (Steckerbrett)
Swaps up to 10 letter pairs before and after the rotors. The plugboard alone adds over 150 trillion possible configurations.
▸ Breaking Enigma
Alan Turing's Bombe exploited cribs (known plaintext) and the no-self-encryption rule to eliminate billions of settings rapidly.
TOTAL CONFIGURATIONS
≈ 1.58 × 10²⁰
158,962,555,217,826,360,000