⚙️ Enigma Simulator

A universal Enigma simulator: 17 historical models (Wehrmacht I, Navy M3, U-boat M4, Norenigma, Sonder-Enigma, commercial D and K, Swiss-K, Railway, Tirpitz, KD with rewirable UKW-D, Zählwerk A28/G31 and the Abwehr G machines), a Custom mode, the Swedish Enigma B (A-133) and the numbers-only Enigma Z30. Use the model menu on every tab. Everything runs in your browser.

Model

Plugboard

Plugs active

Current rotor positions

Result

Group in blocks of 5

The Enigma machine

Enigma is the most famous electromechanical cipher machine and was used extensively by Germany in World War II. It is a rotor machine for polyalphabetic substitution: the substitution changes with every key press because the wheels advance stepwise, the right one on each keystroke and, at certain positions, the neighbour to its left, like a mechanical counter. Inside a wheel each contact is wired to another one; the whole wiring can also be turned against the outer index ring and the turnover notch (the ring setting). Some models add a plugboard that swaps pairs of letters.

Signal path

A key press first moves the wheels. The current then passes the plugboard (if present), the fixed entry wheel (ETW), the rotors and the reflector (UKW), returns by a different route through the rotors, the ETW and the plugboard, and lights a lamp. A letter is never encrypted as itself

Enigma's most serious weakness

and the symmetric path means the same settings decrypt a message.

The family of models

Enigma I (Army, Air Force), M3 (Navy) and M4 “Shark” (U-boats, with a Greek 4th wheel and thin reflector) form the military M-line with plugboard, as do the Norwegian N and the Sonder-Enigma. The commercial line (D, K, Swiss-K, Railway “Rocket”, T “Tirpitz”, KD with rewirable UKW-D) has no plugboard but a settable reflector. The Zählwerk A28/G31 and the Abwehr G machines are gear-driven, with several notches per wheel and a rotating reflector. Special machines are the Swedish Enigma B (28 letters) and the numbers-only Z30.

Wheel drive

Lever-driven machines (pawls and ratchets) show the double-stepping anomaly of the middle wheel; gear-driven machines step regularly like a counter. Rotors VI–VIII have two turnover notches, the T rotors five, the KD rotors nine and the Zählwerk rotors 11 to 17.

Simulator features

17 model presets plus a Custom mode that freely combines entry wheel, wheels, reflector, drive and plugboard, and the maintenance wheel Arb.W. Two input modes: a clickable keyboard with lampboard, where the machine keeps its state and you can re-adjust the wheels in the middle of a message, and a text field that re-encodes the whole text. Ring settings (including the “trivial” ring setting of Enigma D, A-133 and Z30), the same rotor several times, a deactivable plugboard, a rewirable UKW-D for KD and Custom, and a monitor with the signal path. The Enigma-Uhr is not included.

Key and coding procedure

The daily key is the wheel order, ring settings, plugboard and UKW-D wiring. The message key is the start position, chosen for each message. To send it: set the daily key, choose arbitrary start positions (for example WPOS), type the message key (for example CODE) and send WPOS and the output in front of the message. The recipient reverses the steps. Only letters are encrypted: numbers were spelled out, X served as a full stop and “ch” became Q. A message was limited to 250 letters per message key.

Interoperability

Enigma I and M3 are compatible when rotors I–V are used; reflector A was used only in the Enigma I until 1937. An M4 emulates an M3 with reflector B thin and wheel Beta on A/01, or reflector C thin and Gamma on A/01.

Swedish Enigma B and Enigma Z30

The Swedish Enigma B (A-133) has 28 keys including Å, Ä and Ö, no W (written VV) and three wheels. The Enigma Z30 encrypts only digits with wheels of 10 positions. Both use a “trivial” ring setting, where the index ring moves together with the wiring and notch and therefore adds no security. The Z30 Mk II is simulated with gear drive.

Questions and answers

Which model for a puzzle with a three-wheel key? Use M3; for four wheels use M4 (an M4 also works for M3 keys with the combined reflector).

I pasted text but nothing happens. Use the text field mode, which re-encodes the whole content.

Decryption does not match: check that every setting is identical, including plugs, rings and start positions; digits, umlauts and punctuation are not encrypted.

My key uses numbers for the letters: A=1, B=2 … Z=26.

Is it safe for real secrets? No, Enigma is historic and was broken.

Sources and credits

Wiring data come from the Crypto Museum (cryptomuseum.com/crypto/enigma/wiring.htm) and the work of D. Hamer, G. Sullivan, F. Weierud, P. Marks, A. Wik and others. The model list and features are modelled on Daniel Palloks’s “Universal Enigma” JavaScript simulators (people.physik.hu-berlin.de/~palloks/js/enigma/). This is an independent implementation, not a copy of that code.

Enigma Simulator

Parts of the machine

Enigma I

The standard German Army and Air Force machine: three rotors chosen from five, reflectors A, B or C and a plugboard.

I · II · III · UKW-B · AAA: HELLOWORLD → ILBDAAMTAZ

Enigma M3

The Navy version with three rotors chosen from eight (I–VIII) and reflectors B or C.

I–VIII · UKW-B / UKW-C: HELLOWORLD → ILBDAAMTAZ

Enigma M4

The U-boat machine with a fourth, non-stepping Greek rotor (Beta or Gamma) and thin reflectors.

Beta · I · II · III · UKW-B thin · AAAA: HELLOWORLD → ILBDAAMTAZ

Rotor

Rotors are wired discs that scramble each letter. The right one steps on every key; notches carry the movement to the next, including the famous double step.

I: EKMFLGDQVZNTOWYHXUSPAIBRCJ (Q)

Reflector

The reflector sends the signal back through the rotors by another path, so encrypting twice restores the text and no letter can become itself.

B: A↔Y, B↔R, C↔U, D↔H …

Plugboard

The plugboard swaps up to 10 pairs of letters before and after the rotors, adding most of the machine's possible settings.

AB CD EF: A↔B, C↔D, E↔F

Ring setting · Start position

The ring setting shifts the wiring relative to the alphabet ring; the start position is the letter shown in each window at the start of the message.

01 · A / A / A

When to use

Learning how the WWII cipher machine worked
Solving puzzles, escape rooms and CTF challenges
Teaching cryptography and history
Checking messages from historic examples

How to use

Choose the model, rotors, ring settings, start positions, reflector and plugboard
Type on the virtual keyboard or into the message field
Read the result; the lamp shows the last output letter
To decrypt, enter the same settings and type the ciphertext

FAQ

How does the Enigma machine work?

Each key press first moves the rotors, then sends current through the plugboard, three or four rotors, the reflector and back. The result lights a lamp. Because the rotors move on every key, the same letter is encrypted differently each time.

Why can no letter be encrypted as itself?

The reflector pairs every letter with a different one, so the signal can never return to the same letter. This weakness helped codebreakers at Bletchley Park.

How do I decrypt a message?

Enigma is reciprocal: set the machine to the same rotors, rings, start positions and plugboard, and type the ciphertext. The plaintext comes out.

How many settings did Enigma I have?

With three of five rotors, start positions and a 10-cable plugboard there are about 1.59 × 10²⁰ combinations, not counting the ring settings.

Is this simulator accurate?

Yes. It models the real wiring of rotors I–VIII, Beta, Gamma and reflectors A, B, C and thin B and C, including the double-stepping anomaly. It reproduces published test vectors.

Is my text sent to a server?

No. Everything is calculated in your browser.