Self-timed Sensors for Detecting Static Optical Side Channel Attacks

Sophisticated optical side-channel attacks such as Laser Logic State Imaging (LLSI) can destroy an entire system’s security by extracting static signals. LLSI is based on chip failure analysis (FA) techniques and is conducted from the backside of an IC. It provides unlimited number of probes to observe static signals in the hands of an attacker. Several countermeasures have been proposed to prevent optical probing techniques like LLSI, but they have limitations such as complex fabrication steps, large area, etc. which makes them difficult to verify and implement. In this paper, we propose self-timed, CMOS-compatible sensors for easy-to-implement countermeasures to thwart LLSI attack. To conduct LLSI attack, the attacker needs to freeze the clock at a point of interest and modulate the voltage supply line at a known frequency. With these two attack surfaces in mind, we design and simulate clock freeze and voltage modulation detection sensors that can detect LLSI attacks with very high confidence.
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