Silicon Proven 1.29 m x 1.8 m 65nm Sub-Vt Optical Sensor for Hardware Security Applications

Optical fault injection is a type of attack vector targeting cryptographic circuits where the adversary injects faults during system operation to bypass defenses or reveal secret information. Since preventing this kind of attack is generally impractical, most known countermeasures focus on indirect (logic based) or direct detection. Indirect detection mechanisms monitor the effects of optical fault injections in a circuit, whereas direct sensors track the illumination itself. In this paper, we present a compact 1.29 mu m x 1.8 mu m direct optical sensor implemented in 65nm CMOS technology located inside the digital logic fabric. Because it is based on standard CMOS technology, it can be implemented using standard design flow. Measurements on four dedicated chips showed high sensitivity to fault injection attacks: the sensor was 2 to 6 times more sensitive than the combinational logic it protects. As a result of the sub-Vt operation of the transistors, these sensors exhibited post-attack self-recovery ability and high reliability, with a false positive rate under PVT of less than 10(-7).