Spectre and Meltdown: when speed became a side channel

How it worked

A processor guesses which way a branch will go and runs ahead. If the guess is wrong, it discards the results — but not the cache lines it loaded. By timing memory access afterwards, an attacker can tell which data was touched, and so reconstruct secret values byte by byte.

Why it mattered

This was a class of flaws in how CPUs are designed, not a bug in one product. Mitigations cost performance and were added at every layer — microcode, kernels, compilers, browsers — and the field of microarchitectural attacks grew out of it.

Our reading

Analysis — Altumptic's interpretation of the sources below.

• Isolation that relies on hardware doing only what the specification says is weaker than it looks.
• Shared hardware is a shared risk: multi-tenant clouds felt this first.
• Performance optimisations deserve the same threat modelling as security features.

What it means for you

1. Keep microcode and kernels current; side-channel fixes arrive through both.
2. Do not run untrusted code on the same physical cores as secrets when you can avoid it.
3. Use constant-time cryptographic libraries maintained by people who follow this research.