  This paper introduces the Infra-Red, In Situ (IRIS) inspection method, which
uses short-wave IR (SWIR) light to non-destructively "see through" the backside
of chips and image them with lightly modified conventional digital CMOS
cameras. With a ~1050 nm light source, IRIS is capable of constraining macro-
and meso-scale features of a chip. This hardens existing micro-scale self-test
verification techniques by ruling out the existence of extra circuitry that can
hide a hardware trojan with a test bypass. Thus, self-test techniques used in
conjunction with IRIS can ensure the correct construction of security-critical
hardware at all size scales.
