Virtual SG-41 project brings Nazi cipher machine to life in the browser

What showed up in the browser

An enthusiast has recreated the WWII SG-41 cipher machine as an interactive 3D model you can run in a web browser. It has been reported that Martin Gillow describes the work as "part digital preservation, part engineering archaeology, and part 'how on earth did this thing even work?'" The Virtual SG-41 lets users flip switches, inspect cams and levers, and watch enciphering logic play out — not a museum diorama, but close enough to make the hair stand up on an archivist's neck.

Engineering, not exact physics

The SG-41 — the Schlüsselgerät 41, allegedly nicknamed "the Hitler Mill" for its side crank — was intended as an Enigma successor and could print plaintext and ciphertext on twin paper tapes. Gillow began with a 3D scan from the Deutsches Museum and leaned on research from Crypto Museum; he even compared his simulation to a real SG-41 at GCHQ in 2025. He’s candid about limits: "the gears aren't actually turning each other," he says, but the model reproduces the stepping and cam logic by mapping teeth counts and cam shapes so the final enciphering matches physical behaviour.

Why this matters

This is about more than toys and curiosities. Gillow’s work follows his Virtual Colossus and Virtual Lorenz projects and speaks to a larger problem: digital preservation. It has been reported that he’s already planning for longevity, worried about software rot and the fate of browser-based simulations decades from now. The emotional core is clear — a private hobbyist staring at a wartime device and deciding to rescue both its look and its logic for anyone curious enough to click. Who knew that preserving history would end up looking like modern web dev?

Sources: The Register