How to Use the Enigma M3

Initial Setup

  1. Choose rotor types (I-V) for each of the three rotors
  2. Set the ring settings (A-Z) for each rotor - this affects internal wiring but doesn't change the displayed position
  3. Configure the plugboard by connecting up to 10 pairs of letters

Encryption/Decryption

  • Type or click letters to encrypt/decrypt
  • The illuminated lamp shows the encrypted/decrypted letter
  • The rotors will advance automatically with each keystroke
  • The encrypted/decrypted message appears in the panel on the right

Important Notes

  • The Enigma is reciprocal - the same settings decrypt what they encrypt
  • A letter can never encrypt to itself due to the reflector
  • Plugboard connections swap letters both before and after the rotor encryption
  • Record your settings - you'll need the same ones to decrypt the message

How the Enigma Machine Works

Basic Principle

The Enigma machine is an electro-mechanical device that performs polyalphabetic substitution - each letter is encrypted differently depending on its position in the message. This was revolutionary because simple substitution ciphers (where A always becomes X, for example) are easily broken.

Encryption Path

  1. Plugboard (Steckerbrett): When a key is pressed, the electrical signal first passes through the plugboard. If the letter is connected to another letter, they swap. This happens both at the start and end of the encryption process.
  2. Rotors (Walzen): The signal then passes through three rotors from right to left. Each rotor performs a simple substitution, but because the rotors move, this substitution changes with each keystroke. The right rotor steps with each key press, the middle rotor steps when the right rotor completes a revolution, and the left rotor steps when the middle rotor completes a revolution (similar to an odometer).
  3. Reflector (Umkehrwalze): After passing through all three rotors, the signal hits the reflector, which performs another fixed substitution and sends the signal back through the rotors in reverse. This is why the Enigma is reciprocal - if A encrypts to X, then X will encrypt to A with the same settings.
  4. Return Path: The signal travels back through all three rotors from left to right, but following different paths due to the rotor wiring. Finally, it passes through the plugboard again before lighting up the lampboard.

Key Components

  • Rotor Selection: Each rotor has different internal wiring. The M3 had five possible rotors (I-V) to choose from for the three positions, creating 60 possible rotor arrangements.
  • Ring Settings (Ringstellung): Each rotor's wiring can be rotated relative to its alphabet ring, adding another layer of complexity. This affects when the next rotor will step.
  • Starting Positions: Each rotor can be set to any starting position (A-Z), providing the initial state for the message.
  • Plugboard: Up to 10 pairs of letters can be swapped, adding an enormous number of possible configurations. This was unique to the military version and significantly increased the machine's security.

Security Features

  • No letter can encrypt to itself due to the reflector's design - this was actually a weakness that helped codebreakers.
  • The encryption changes with each letter due to the rotor movement, creating an extremely long cipher period.
  • With all possible settings combined (rotor selection, ring settings, starting positions, and plugboard), the M3 had approximately 158,962,555,217,826,360,000 different possible configurations.