A Twofold Clock and Voltage-Based Detection Method for Laser Logic State Imaging Attack

Powerful side-channel analysis (SCA) attacks based on failure analysis (FA) techniques can bypass conventional countermeasures on integrated circuits (ICs) and, therefore, break the entire system’s security. Laser logic state imaging (LLSI) from the IC backside is an example of such attacks, making the contactless probing of static on-die signals possible. Several countermeasures have been proposed to prevent optical probing attacks, such as LLSI. However, these schemes are designed according to the laser properties and its impact on transistors, and hence, they have complex fabrication steps and large area overhead. As a result, they are difficult to verify and implement. In this article, we propose a twofold detection self-timed sensor, which is the first attempt, to our knowledge, for an easy-to-implement circuit-based countermeasure to thwart LLSI attacks. To perform LLSI, the attacker needs to freeze the clock at a point of interest and modulate the voltage supply line at a known frequency to leak the state of transistors through laser light reflections. With these two attack requirements in mind, we design, simulate, and implement clock- and voltage-based sensors that can detect LLSI attacks with very high confidence.