Reconfigurable Run-Time Hardware Trojan Mitigation for Logic-Locked Circuits

Globalized outsourcing of integrated circuit manufacturing has introduced potent security threats such as unauthorized overproduction and hardware Trojan insertion. An approach that is used to protect circuit designs from overproduction is logic locking, which introduces key inputs to a digital circuit such that only the correct key will allow the circuit to work properly and all others will cause unintended functionality. On the other hand, the majority of the existing methods to tackle hardware Trojans are in the realm of proactive prevention or static detection, but a more challenging problem, which is the run-time mitigation of the Trojans inserted in a zero-trust design flow, is yet to be solved. In this work, we look through the lens of logic locking with the goal of introducing online reconfigurability into a design and apply the fundamental principles of fault tolerance and state traversal to create an effective mitigation tactic against hardware Trojans. Redundancy is inserted at low-controllable states to create trap states for the attackers, and key inputs are added to select the active path. The strength of our proposed approach lies in its ability to circumvent Trojan payloads transparently at run-time with only a slight overhead, as demonstrated by experiments run on over 40 benchmarks of varying sizes. We also demonstrate viability when combined with secure logic locking methods to provide multi-objective security.