A Secure Scan Controller for Protecting Logic Locking

The globalized supply chain in the Integrated Circuit (IC) industry raises several security concerns such as overproduction, IP piracy and Hardware Trojan insertion. Logic locking has emerged as a potential countermeasure to address these issues. However, its efficiency is challenged by various attacks, especially oracle-guided attacks based on Boolean Satisfiability (SAT) solvers. These attacks rely on the possibility for an attacker to control and observe in the field the internal state of a functional IC, which acts as an oracle. This ability to control/observe the IC states is offered by scan chains, typically used for IC production testing. In this paper, we propose a method, complementary to logic locking, to prevent such attacks. This method introduces a scan chain controller with a key-based authentication mechanism, in order to prevent unauthorized access to the scan chains once the IC is deployed in the field. The solution can be coupled with any logic locking technique at the cost of negligible area overhead. Furthermore, it is secure against state-of-the-art attacks and supports full testing.