Blog · page 9
Notes on engineering, design, and everything in between.
How a CDN puts your content next door
A site hosted in Virginia can serve you images from a machine in your own city. This covers the three jobs of a CDN, why cache hit ratio is the only metric that really matters, what else edge nodes do, and why CDNs fight to get into internet exchanges.
Three ways classical cipher tools go quietly wrong
Caesar, Vigenere and Atbash all look like table lookups, but case handling, non-letter characters and key alignment each fail silently when done wrong.
Where a data center's power comes from
The thing a data center fears is not downtime, it is a blackout. This covers the full chain from the utility feed to the rack, the three UPS topologies, why a diesel generator must carry load within ten seconds, and how the PUE number gets gamed.
Debian DSA-6045: a poisoned resolver can also break DNSSEC
Debian issued DSA-6045-1 for pdns-recursor, fixing CVE-2026-52690 and related issues. An attacker can forge answers so the resolver marks an authoritative server as EDNS-incapable, which makes DNSSEC validation fail.
NTP and time sync: the internet's heartbeat
How far apart can two clocks be before things break? This covers how NTP derives an offset from four timestamps, why stratum measures distance rather than accuracy, why leap seconds are so awkward, and what happens when time gets poisoned.
Photolithography: printing circuits onto silicon
The smallest features on a modern chip are a few nanometres across, smaller than most viruses. They are not carved but printed with light. This covers the four-step cycle, the Rayleigh criterion, the multi-patterning era, and why EUV is so hard.