termigma

A terminal simulator of the Wehrmacht/Kriegsmarine Enigma machine — rotors, plugboard, lampboard, and a live signal-path monitor, all in your terminal.

pip install termigma
termigma

No dependencies on Linux/macOS (just the standard library's curses). On Windows, pip install termigma pulls in windows-curses automatically.

What it does

You type a letter, it lights up on the lampboard, and the signal path panel shows exactly how it got there: plugboard → entry wheel → through each rotor → reflector → back through the rotors → entry wheel → plugboard → lamp. The rotors step on every keypress, including the historically correct middle-rotor "double step," and there's no undo — same as the real machine.

It covers three points in the machine's history:

• Enigma I (Army/Air Force) — 3 rotors chosen from I–V
• M3 (Army/Navy) — 3 rotors chosen from I–VIII
• M4 "Shark" (U-boats) — adds a fourth, non-stepping Beta/Gamma wheel and a thin reflector

Plus a commercial-style mode that demonstrates the real quirk of commercial Enigmas: no plugboard, and an entry wheel wired in keyboard (QWERTZU) order instead of straight A–Z.

Controls

Terminal needs to be at least 108×34 or it'll ask you to resize.

Why it looks the way it does

Real Enigmas didn't have an undo button, a Ctrl-Z, or a way to peek inside while it ran. This tries to keep that feel — the rotors always turn, the plugboard is genuinely optional depending on which model you pick — while also showing you the one thing the real machine couldn't: what's happening electrically at every stage, for every keystroke.

Project layout

src/termigma/engine.py   the machine itself — no curses, fully unit-testable
src/termigma/tui.py      curses rendering and the input loop
tests/test_engine.py     pytest suite (reciprocity checks, stepping, etc.)
data/wiring_tables.json  the historical wiring data, with sourcing notes

Running from source

git clone https://github.com/rexackermann/termigma
cd termigma
pip install -e ".[dev]"
pytest
termigma

Accuracy

The rotor and reflector wiring (rotors I–VIII, the M4 Beta/Gamma wheels, and reflectors B/C plus their thin M4 counterparts) is the widely published historical data, checked here against a known reference test vector and a set of round-trip (reciprocity) tests — see tests/test_engine.py.

What's not included: exact wiring for the more exotic commercial and national variants (Enigma K, Enigma D, Swiss-K, Railway, Tirpitz, Norenigma, Sonder-Enigma, the Abwehr G-machines). This project doesn't have confidently sourced wiring for those, and a guess dressed up as fact is worse than an honest gap. The "commercial-style" preset demonstrates the real no-plugboard / QWERTZU-entry-wheel behavior of commercial machines but reuses the Enigma I rotor set rather than true K/D rotors. See data/wiring_tables.json for the full sourcing note, and cross-check the Crypto Museum's Enigma pages if you need one of those specific machines to be byte-exact.

Credits

• Inspired by Daniel Palloks' Universal Enigma, a browser-based simulator covering a much wider range of historical Enigma variants than this project attempts.
• Enigma explainer video: https://www.youtube.com/watch?v=JsBZOcqZerk — for inspiration.
• Built with help from Claude (Anthropic).

License

MIT — see LICENSE.