Is Backside the New Backdoor in Modern SoCs?: Invited Paper

Modern integrated circuits (ICs) possess several countermeasures to safeguard sensitive data and information stored in the device. In recent years, semi-invasive physical attacks based on optical debugging techniques have proven to be capable of easily bypassing these security measures implemented in the chip. Optical attacks can reveal the data stored in memory, cache and register through various methods such as photon emission analysis, laser fault injection, laser voltage probing, and thermal laser stimulation. The above-mentioned methods, which employ laser scanning microscopy and photon emission microscopy, are effective because the silicon substrate is transparent to near-infrared (NIR) photons. Therefore, the most vulnerable part of an IC to optical attacks is the backside, where the chip's transistors can be accessed and probed with a NIR laser beam. Although different optical attack detection and avoidance mechanisms have been proposed, many can be circumvented and none are universal solutions for all types of optical attacks. In this study, we present a taxonomy of the different types of optical attacks and the security threats posed by each type. Then we discuss the existing prevention-detection based solutions to optical probing attacks which will set the future research direction.