Defined model
Guess an Enigma I configuration with two unknown rings
- Probability:
- 9.31 × 10⁻²²%
- Odds:
- 1 to (1.07 × 10²³)
- dBan
- −230.3 dBan
Leave two Enigma I rotor rings unknown and two more hidden settings multiply an already vast field of rotor and plugboard possibilities. One guess has to find the exact combination.
Calculation
N = 158,962,555,217,826,360,000 × 26² = 107,458,687,327,250,619,360,000. p = 1/N
Assumptions
The left rotor ring is fixed to a known reference because its equivalent offset is absorbed into the starting-position convention. The middle and right rings each have 26 settings. The reflector and wiring are known. The rest of the counted configuration contains three ordered rotors from five, one of 26 starting positions for each rotor, and exactly 10 plugboard cables that pair 20 letters. Six letters remain unplugged. All mechanically possible rotor orders count, regardless of historical operating restrictions. Effective cryptographic strength also depended on attack methods and message context.