O'clock: lock the clock via clock-gating for SoC IP protection

Existing logic locking techniques can prevent IP piracy or tampering. However, they often come at the expense of high overhead and are gradually becoming vulnerable to emerging deobfuscation attacks. To protect SoC IPs, we propose O'Clock, a fully-automated clock-gating-based approach that 'locks the clock' to protect IPs in complex SoCs. O'Clock obstructs data/control flows and makes the underlying logic dysfunctional for incorrect keys by manipulating the activity factor of the clock tree. O'Clock has minimal changes to the original design and no change to the IC design flow. Our experimental results show its high resiliency against state-of-the-art de-obfuscation attacks (e.g., oracle-guided SAT, unrolling-/BMC-based SAT, removal, and oracle-less machine learning-based attacks) at negligible power, performance, and area (PPA) overhead.