https://cs.lozic.me/areas/security/Recent content in Security on CS TheoremsHugoen-usFri, 18 Jun 2027 12:00:00 +0100https://cs.lozic.me/posts/t063-the-byzantine-generals-problem/Fri, 18 Jun 2027 12:00:00 +0100https://cs.lozic.me/posts/t063-the-byzantine-generals-problem/<h2 id="symptom">Symptom</h2> <p>A node in your cluster is not down. It is worse than down.</p> <p>Its disk is returning corrupted blocks that pass the checksum because the checksum is corrupted too. Or a NIC with a firmware bug is duplicating and reordering frames. Or a bad memory module flipped a bit in a config value and the node now believes it owns a shard it does not. Or someone has root on one machine.</p>https://cs.lozic.me/posts/t011-rices-theorem/Fri, 16 Oct 2026 12:00:00 +0200https://cs.lozic.me/posts/t011-rices-theorem/<h2 id="symptom">Symptom</h2> <p>The security team asks for a scanner with no false positives and no false negatives. Every piece of malware caught, nothing legitimate quarantined.</p> <p>The platform team asks whether the analyzer can flag every function that performs I/O, so the pure ones can be cached automatically.</p>