SIGABA Machine Simulator
Simulate SIGABA online: configure all 15 rotors, encrypt and decrypt with CSP-889 or CSP-2900, and inspect the irregular stepping. Educational wiring is disclosed.
Open
- free
- no sign-up
- on device
Enigma Machine Simulator
Simulate Enigma I, M3 and M4 encryption and decryption in your browser — free, with no sign-up, and a visible signal path for each letter. Set the full key, type a message and follow each keystroke through the rotors and reflector.
Machine setup
IA01
IIA01
IIIA01
Reflector: B · Plugboard pairs: 0
Encode or decode
Enigma is reciprocal: use the same initial settings to decipher the output. It cannot recover an unknown key.
0 / 5000
0 letters
Follow the signal
Inspect each keypress: wheels step first, then current flows through the plugboard, rotors and reflector, and returns to the lamp.
Type a letter above or use the keyboard below to see its electrical path.
Try the lampboard keyboard
All processing happens in this tab. Messages are not uploaded or saved. Enigma is a historical cipher, not safe for modern secrets.
Historical wiring and stepping references: Crypto Museum · David Hamer
How it works
- Choose the machine and keySelect Enigma I, Naval M3 or M4. Set distinct rotors from left to right, their ring settings and starting windows, the reflector and up to ten plugboard pairs.
- Type or paste a messageThe simulator transforms A–Z as you type. Punctuation and spaces can stay visible, be omitted, or the letters can be grouped in fives. Only A–Z advances the wheels.
- Trace or reverse itStep through the signal path and final windows. To decrypt, restore exactly the same starting key and enter the ciphertext; the same machine operation reverses it.
Questions
What is an Enigma machine simulator?
It is a browser model of the German military rotor cipher machine. This page reproduces Enigma I, Naval M3 and Naval M4 using their documented rotor and reflector wirings. You can enter your own text, configure the key and inspect the signal path instead of just reading a historical description.
How does the Enigma machine encrypt a letter?
Before each A–Z keypress, the right rotor advances and sometimes moves its neighbors; the middle rotor can advance on two successive presses (double-stepping). Current travels through the plugboard, the rotors from right to left, the reflector, back through the rotors and the plugboard, then lights a letter. The changed wheel positions make repeated letters encrypt differently.
How do I decrypt an Enigma message?
Use the same model, reflector, rotor order, ring settings, plugboard pairs and initial window positions used for encryption. Enter the ciphertext from the beginning of the message. Enigma is reciprocal, so the encrypt and decrypt operations are identical; changing even one setting gives different text. This simulator does not discover an unknown key or crack intercepted messages.
What is the difference between ring setting and rotor position?
Ringstellung moves the alphabet ring relative to the rotor's internal wiring; it changes the electrical offset. Grundstellung is the visible starting letter in each window before the first keypress. Both are part of the key. This page shows ring settings as 01–26 and A–Z, and the window letters separately.
What are the plugboard and reflector for?
The plugboard (Steckerbrett) swaps up to ten disjoint pairs of letters before and after the rotor path. The reflector (Umkehrwalze) returns the signal through the rotors in reverse, which makes encryption reciprocal. With the standard military reflectors, a letter can never encrypt to itself.
What changes in the four-rotor Enigma M4?
Naval M4 adds a thin Beta or Gamma wheel at the left and uses a thin B or C reflector. That Greek wheel has a settable ring and starting position but never steps during a message; the three ordinary rotors still step, including the middle rotor's double-step. M3 and M4 can choose among rotors I–VIII; Enigma I uses I–V.
Why does spacing or punctuation not change the result?
The historical keyboard enciphered letters A–Z. In this tool, spaces, digits, punctuation and non-Latin letters either remain untouched or are hidden by the output format, and they never advance a rotor. For a historically styled transmission, choose letters only or groups of five. Accented letters are not transliterated automatically.
Who broke Enigma, and is it secure today?
Polish mathematicians Marian Rejewski, Jerzy Różycki and Henryk Zygalski made foundational breakthroughs; Allied teams, including Bletchley Park, later expanded the work. The tool simulates known-key operation, not cryptanalysis. Enigma is historically important but entirely unsuitable for protecting modern secrets.
Is this tool free?
Yes. This tool is free, with no sign-up and no daily limits.
Do I need an account?
No. You can use this tool without an account.
Is my input sent anywhere?
No. This tool runs in your browser. Your input and results never leave your device unless you choose to share them.
Related tools
Fialka M-125 Simulator
Simulate the Fialka M-125 online: set 10 wheels and a punched card, encrypt or decrypt Cyrillic text, and inspect every rotor step.
Open
Text Encryptor
Encrypt and decrypt messages in any language with a random 256-bit key. Copy readable Base32 ciphertext; everything runs in your browser.
Open