PASS: Pattern-Sequence-Authentication-Based Secure Scan Against Reverse Engineering Attacks

Scan-based testing is a widely used design for testability method to ensure the ease of testing. In this method, the enhanced observability and controllability provided by the inserted scan chains significantly improve the ability to analyze circuit data. However, since the enhanced testability can be exploited by malicious users as a backdoor for attacks, countermeasures need to be implemented to prevent scan chain access by unauthorized users. Although much research on secure scan designs has been conducted, most proposed methods are vulnerable to architecture exposure by reverse engineering. Moreover, even the latest proposed methods are affected by issues related to untrustworthy test engineers. This study proposes a pattern-sequence-authentication-based secure scan that not only defends against reverse engineering-based attacks but also prevents test engineers from launching attacks using additional patterns other than the given pattern. The proposed method effectively addresses the issue of secret key leakage through valid test patterns by untrustworthy test engineers, which is a limitation of the existing methods. The experimental results show that the proposed method effectively defends against existing attack techniques and ensures high security performance.