For the past ten years I’ve been working on Virtual Colossus, a long‑term digital‑preservation project to recreate early computing and cryptographic machines as interactive, historically accurate simulations. My latest piece is a fully interactive 3D reconstruction of the SG‑41 (“Hitlermühle” or Hitler Mill) using three.js. It’s a cipher machine that doesn’t get much attention compared to Enigma, partly because so few survived and partly because its internal mechanics are… complicated.
I wanted to create something that wasn’t just a visual model but a functional reconstruction:
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every wheel, lever, and pawl is animated based on the real mechanism
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the stepping logic is implemented from historical documentation
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you can type plaintext and watch the machine encrypt in real time
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the whole thing runs in the browser with no plugins
This project started as a way to understand how the SG‑41 actually worked, and it turned into a deep dive into mechanical cryptography, wartime engineering constraints, and some surprisingly elegant design choices.
If you’re curious about cipher machines, mechanical logic, or just like seeing obscure historical tech brought back to life, you can try it here:
https://sg41.virtualcolossus.co.uk/VirtualSG41
or find out more about the technical details or other simulations
