A LITTLE MACHINE FOR SECRETS
One letter in. Another letter out.
But with every keypress, the rules change.
Turn the rotors. Send a secret.
Follow the electricity.
Swipe the diagram to follow the full circuit ↔
THE SECRET IS IN THE MOVEMENT
Enigma was an electromechanical cipher machine. Instead of replacing A with the same letter every time, it sent an electrical signal through moving, wired wheels.
The right rotor steps before each letter is encoded. At a notch, it advances the middle rotor. The middle rotor’s own notch makes it and the left rotor step together, so the middle rotor can move on two consecutive keypresses.
The reflector sends the signal back through the rotors along a different path. One consequence: a letter can never encrypt to itself. Try a string of A’s and look for an A in the result.
Reset to the same starting positions and keep the same plugboard. Type the ciphertext, and the original message comes back. “Decode this result” does exactly that for you.
The starting positions matter. Continuing from the final rotor positions won’t decode your message.
This toy uses the Enigma I wirings for rotors I–II–III, reflector B, an identity entry wheel, and authentic double stepping. Rotor order and ring settings (AAA) are fixed; starting positions and plugboard pairs are adjustable. The signal diagram is a schematic, not the physical layout of the machine.
For readability, spaces and punctuation are preserved and do not move the rotors. The historical machine enciphered only letters. Everything is processed in your browser. This is an educational historical cipher, not modern secure encryption.
Explore the rotor wiring documented by David Hamer, Virtual Enigma’s technical explanation, and Hamer’s explanation of double stepping (PDF).