Defined model
Guess an Enigma M4 configuration with known rings
- Probability:
- 2.16 × 10⁻²¹%
- Odds:
- 1 to (4.63 × 10²²)
- dBan
- −226.7 dBan
The naval Enigma M4 adds a fourth rotor. With its ring settings known, the rotors, starting positions, and plugboard still leave a vast field of possible setups for one exact guess.
Calculation
N = [26! / (6! × 10! × 2¹⁰)] × P(8, 3) × 2 × 26⁴ = 46,289,896,079,431,036,032,000. p = 1/N
Assumptions
The reflector, wiring, and ring settings are known. The counted configuration contains three ordered rotors from eight, a Beta or Gamma Greek rotor, one of 26 starting positions for each of the four rotors, and exactly 10 plugboard cables that pair 20 letters. Six letters remain unplugged. The reflector is fixed. All mechanically possible rotor orders count, regardless of historical operating restrictions. Effective cryptographic strength also depended on attack methods and message context.