In this paper, we introduce DFSSD, a novel logic locking solution for sequential and FSM circuits with a restricted (locked) access to the scan chain. DFSSD combines two techniques for obfuscation: (1) Deep Faults, and (2) Shallow State Duality. Both techniques are specifically designed to resist against sequential SAT attacks based on bounded model checking. The shallow state duality prevents a sequential SAT attack from taking a shortcut for early termination without running an exhaustive unbounded model checker to assess if the attack could be terminated. The deep fault, on the other hand, provides a designer with a technique for building deep, yet key recoverable faults that could not be discovered by sequential SAT (and bounded model checker based) attacks in a reasonable time.
@article{arxiv.2002.07857,
title = {DFSSD: Deep Faults and Shallow State Duality, A Provably Strong Obfuscation Solution for Circuits with Restricted Access to Scan Chain},
author = {Shervin Roshanisefat and Hadi Mardani Kamali and Kimia Zamiri Azar and Sai Manoj Pudukotai Dinakarrao and Naghmeh Karimi and Houman Homayoun and Avesta Sasan},
journal= {arXiv preprint arXiv:2002.07857},
year = {2020}
}