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Lukáš Czerner
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Posts

Notes on systems, security, and how trust fails.

2026 4 posts
Oct 10 Tailscale Behind OPNsense: Why Everything Goes Through DERPTailscale starts every connection on a DERP relay and then tries to upgrade it to a direct WireGuard path. Behind OPNsense that upgrade kept failing in my lab, and the reason was the way pf picks the outside port for UDP. This is how the hole punching works, and the three NAT modes that make or break it.
cybersecurity tools
Feb 27 Sovereignty Cannot Be OutsourcedDigital sovereignty cannot mean strategic decisions influenced from outside Europe. Open source is part of the solution - but sovereignty requires control, ownership, and leadership rooted in Europe.
Europe geopolitics open source
Feb 17 The Long Road to Fixing TLS Certificate RevocationFor most of the web's history, revoking a compromised TLS certificate was theoretically possible but practically useless. This is the story of how every attempted fix failed - and how a clever combination of data structures and Certificate Transparency finally made revocation work.
cybersecurity
Feb 8 How Modern Wars Are Really Won: Lessons from O'Brien's War and PowerModern wars aren't won on battlefields - they're won in factories, ports, and alliances. Insights from Phillips Payson O'Brien's War and Power on systemic warfare.
geopolitics
2024 1 post
Dec 27 AGI and Paperclips in 2025Sam Altman says AGI is coming next year, but also that it won't matter much - a convenient pivot from world-changing singularity to incremental product update that raises questions about whether we're getting the future we were promised, or just another subscription service.
AI
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