Memory Cost Analysis for Sequential Logic Locking FSMLock

J. Evans, M. Łukowiak (Rochester Inst. of Techn., USA)

FSMLock is a memory-based finite state machine locking methodology that uses memory and private key cryptography to protect FSM-based IP. It was designed to counteract the several threats found within the IC design industry, and was assembled into its own toolset to be customizable according to provided parameters of a protected FSM. Though FSMLock has seen significant changes and improvements, including the addition of Finite State Machine Input Multiplexing (FSMIM), there are still several considerations related to its cost (size), performance, and usability. This paper provides detailed analysis of the theory behind memory-based FSM implementations, like FSMLock, to determine all important considerations and constraints for input FSM features based on a given memory size. Given that memory usage is a critical constraint on the usability of FSMLock, designing FSMs for optimized memory usage and utilization is key.