Enigma (step-by-step)

World War 2 rotor encryption machine

Inspect the encryption and decryption of the Enigma cipher machine step by step.

The configuration of the Engima cipher machine has three parts:

  1. The wheels with overflows and offsets (via the whell rings),
  2. The reflector wheel, and
  3. The plugboard.

Parts of the configuration can be treated as public knowledge or as part of the key.

Each wheel is the permutation of the letters. There are five permutations provided but you can create your own as long as it is a real permutation (doing so you leave the default executions of the historical Enigmas). The permutation can be offset to increase the number of possible wheels to use (instead of 5 you have 5 × 26).

Additionally you must specify at which letter an overflow to the next wheel will happen.

The offset allows to rotate the permutations relative to the alphabet. With offset 1 no shifting takes place. With offset 2 B will be used instead of A, C instead of B and so on.

The reflector wheel must map each letter to a different one. Otherwise all encryption steps will be undone on the way back.

You can swap additional letters.