BYTETOOLS

Enigma Machine Simulator

A working Enigma I / M3 simulator with rotors I–V, reflectors A, B and C, ring settings, start positions and a full plugboard. Runs in your browser.

Encryption and decryption are the same operation on an Enigma, so pasting the output back in with identical settings returns the original text. Everything runs locally in your browser. This is a historical curiosity, not a way to protect anything — Enigma traffic was being read routinely by 1941.

Wheel order (left to right, as seen from the front)

Rotor I steps the next wheel on Q→R; rotor II steps the next wheel on E→F; rotor III steps the next wheel on V→W.

Ring settings (Ringstellung)

The ring rotates the alphabet against the internal wiring without moving the turnover notch, so it shifts where in the message each carry happens.

Start positions (Grundstellung)

Output

Type a message above. With the default settings, twenty-five letter A keypresses come out as BDZGOWCXLTKSBTMCDLPBMUQOF.

How a keypress travels

  1. The wheels step first — the right wheel every time, the others when a notch lines up.
  2. The plugboard swaps the letter if a cable is attached to it.
  3. The current crosses the right, middle and then left wheel.
  4. The reflector sends it back through a fixed set of pairings.
  5. It returns through the left, middle and right wheel, then through the plugboard again.
  6. Because the reflector never pairs a letter with itself, no letter can ever encipher to itself — the flaw Bletchley Park built its cribs on.

Self-test passed: wheels I II III with UKW-B at AAA turn twenty-five A's into the published BDZGOWCXLTKSBTMCDLPBMUQOF.

What is the Enigma Machine Simulator?

The ByteTools Enigma Machine Simulator recreates the German Army Enigma I and its naval three-rotor sibling, the M3.

  • Rotors I–V with authentic wiring and turnover notches
  • Reflectors UKW-A, UKW-B and UKW-C
  • Ring settings, start positions and up to 13 plugboard pairs
  • Correct stepping, including the middle-rotor double step
  • Output also grouped in fives, as radio operators transmitted it
  • Random day settings, a copyable settings sheet and a live rotor position readout

How to use the Enigma Machine Simulator

  1. 1

    Pick the three wheels in the order they sat in the machine, left to right — each must be different.

  2. 2

    Choose a reflector, then set the ring settings and the start position for each wheel.

  3. 3

    Add plugboard pairs such as 'AM FI NV', or leave the box empty for no cables.

  4. 4

    Type your message; only letters are enciphered, exactly as on the real machine.

  5. 5

    Copy the output and the settings summary — you need both to decrypt it later.

About the Enigma Machine Simulator

The ByteTools Enigma Machine Simulator recreates the German Army Enigma I and its naval three-rotor sibling, the M3. Choose any three of rotors I to V with their published wiring alphabets and turnover notches, pick reflector A, B or C, set the Ringstellung and start positions, and wire up to thirteen plugboard pairs. Each keypress steps the wheels — including the famous middle-rotor double step — before the current is routed through the plugboard, all three rotors, the reflector and back again.

Because the reflector is a set of fixed pairings, encryption and decryption are the same operation. Feed the output back in with identical settings and your plaintext returns, which is exactly how a receiving operator worked. It is also why no letter can ever encipher to itself — the flaw Bletchley Park built its cribs on, and the reason this is a fascinating machine rather than a secure one.

Everything runs 100% locally in your browser, so nothing you type is uploaded. The simulator is verified against documented historical messages, including the 1930 Enigma Instruction Manual example and the first Operation Barbarossa signal of 1941, both of which it decrypts correctly.

Frequently asked questions

How do you decrypt an Enigma message?

With the same settings you encrypted it with. The reflector makes the machine its own inverse, so typing the ciphertext into a machine set to the original wheel order, rings, start positions and plugboard gives you the plaintext back.

What is the Ringstellung and how is it different from the start position?

The ring setting rotates the alphabet ring against the wheel's internal wiring without moving the turnover notch, so it shifts where in the message each carry happens. The start position is simply which letter is showing in the window when you begin.

What is the Enigma double step?

When the middle wheel is sitting on its own turnover notch, the next keypress advances the middle and left wheels together — so the middle wheel moves twice in consecutive presses. It is a quirk of the pawl mechanism, and any accurate simulator has to reproduce it.

Why can a letter never encrypt to itself on an Enigma?

The reflector pairs letters, so the current always comes back on a different wire than it went out on. That single property gave codebreakers a reliable way to rule out crib positions, and it was central to how Bletchley Park attacked the traffic.

Is the Enigma cipher secure today?

Not remotely. Its whole key space is smaller than a modern 80-bit key and is searched in seconds on a laptop. Treat this simulator as a history lesson and a puzzle tool, never as a way to protect real information.

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