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Nils Lehnen

IT security for critical healthcare infrastructure, and for the small businesses nobody else looks after. Since 2017, from Düsseldorf.

I work on the load-bearing parts: fail-closed defaults, audit trails that hold up under scrutiny, and software that runs inside your own network rather than somebody else's. Most of what I publish comes out of that work. If a tool has to be trusted with something that matters, it should be possible to read it and check it.

Current work

Flowfin

Native clients and server plugins for Jellyfin, held to a speed budget written as numbers a build can miss rather than as an intention. Twelve plugins, a shared design system, and colour presets for each form of colour vision deficiency rather than a single accessible mode.

jellyfin-plugin-sso · C#, .NET 9

Single sign-on for Jellyfin over OpenID Connect and SAML 2.0, with verified setup guides for Keycloak, Authelia, authentik, Dex, Pocket ID, Kanidm and Zitadel. A security-first continuation of the archived 9p4/jellyfin-plugin-sso.

cudec · C++, CUDA

GPU decompression that is auditable and fuzz-tested. LZ4 batch decoding on NVIDIA hardware today; Snappy, GDeflate and Zstd planned.

swarm.asm · x64 assembly

A particle-life engine written entirely in hand-written x64 assembly with AVX2. The target is a million particles at 60 frames per second, with no GPU, no dependencies and one small executable.

linux · C

Working tree for Linux kernel development and upstream contributions.

Languages

C, C++ with CUDA, C#, Rust, and x64 assembly. Different problems, the same habit: make the illegal state impossible to write down, then check that it is.

Support

If something here saved you time, you can buy me a coffee.

See NOTICE.md for the intended-use notice.

About

My GitHub profile README - security-first systems programming: fail-closed, auditable, self-hosted

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