Fundamentals of Logic Locking

Logic locking is an active IP protection technique that has been widely used during the last two decades as one crucial step of the IC supply chain to provide protection against threats like RE, IP piracy, and even hardware Trojan insertion. When logic locking is in place, the targeted design will go under some modifications, including having additional gates inserted into the design and controlled by a new set of inputs, having additional sequences of operations needed for the logic locking part, and having different operational modes (locked vs. unlocked). For a logic-locked design, the functionality will become hidden from any untrusted entity throughout the IC supply chain, and it requires activation before releasing in the market or in the field. This chapter covers the fundamentals of logic locking, how it can be implemented, how it works, and how the activation will be done. Additionally, this chapter covers how logic locking may be targeted by adversaries to circumvent the protection provided by this approach. The purpose of this chapter is to provide fundamental information about logic locking, giving readers insight into the mechanisms that can be used for logic locking once we move forward.