Infra-Red, In Situ (IRIS) Inspection of Silicon « bunnie's blog

How can you know that the integrated circuits you are buying do not have malicious code in them, at a hardware level? This is a devilishly hard problem to deal with.

IRIS is a necessary complement to logic-level hardening methods, because logic-only methods are vulnerable to bypasses and emulation. In this scenario, a hardware trojan includes extra circuitry to evade detection by spoofing self-tests with correct answers, like a wolf carrying around a sheep’s costume that it dons only when a shepherd is nearby. Since IRIS can constrain meso-scale to macro-scale structure, we can rule out medium-to-large scale circuit modifications, giving us more confidence in the results of the micro-scale verification as reported by logic-level hardening methods.

It is one thing to source your chips from places you trust, but it is still relying on trust. How can you validate the integrity of every instance of a chip for high-security use cases?