Biblio

The IEEE Std. 1687 (IJTAG) was designed to provide on-chip access to the various embedded instruments (e.g. built-in self test, sensors, etc.) in complex system-on-chip designs. IJTAG facilitates access to on-chip instruments from third party intellectual property providers with hidden test-data registers. Although access to on-chip instruments provides valuable data specifically for debug and diagnosis, it can potentially expose the design to untrusted sources and instruments that can sniff and possibly manipulate the data that is being shifted through the IJTAG network. This paper provides a comprehensive protection scheme against data sniffing and data integrity attacks by selectively isolating the data flowing through the IJTAG network. The proposed scheme is modeled as a graph coloring problem to optimize the number of isolation signals required to protect the design. It is shown that combining the proposed approach with other existing schemes can also bolster the security against unauthorized user access as well. The proposed countermeasure is shown to add minimal overhead in terms of area and power consumption.

The security of logic locking has been called into question by various attacks, especially a Boolean satisfiability (SAT) based attack, that exploits scan access in a working chip. Among other techniques, a robust design-for-security (DFS) architecture was presented to restrict any unauthorized scan access, thereby, thwarting the SAT attack (or any other attack that relies on scan access). Nevertheless, in this work, we successfully break this technique by recovering the secret key despite the lack of scan access. Our security analysis on a few benchmark circuits protected by the robust DFS architecture demonstrates the effectiveness of our attack; on average 95% of the key bits are correctly recovered, and almost 100% in most cases. To overcome this and other prevailing attacks, we propose a defense by making fundamental changes to the robust DFS technique; the new defense can withstand all logic locking attacks. We observe, on average, lower area overhead ( 1.65%) than the robust DFS design ( 5.15%), and similar test coverage ( 99.88%).

Digital fingerprinting refers to as method that can assign each copy of an intellectual property (IP) a distinct fingerprint. It was introduced for the purpose of protecting legal and honest IP users. The unique fingerprint can be used to identify the IP or a chip that contains the IP. However, existing fingerprinting techniques are not practical due to expensive cost of creating fingerprints and the lack of effective methods to verify the fingerprints. In the paper, we study a practical scan chain based fingerprinting method, where the digital fingerprint is generated by selecting the Q-SD or Q'-SD connection during the design of scan chains. This method has two major advantages. First, fingerprints are created as a post-silicon procedure and therefore there will be little fabrication overhead. Second, altering the Q-SD or Q'-SD connection style requires the modification of test vectors for each fingerprinted IP in order to maintain the fault coverage. This enables us to verify the fingerprint by inspecting the test vectors without opening up the chip to check the Q-SD or Q'-SD connection styles. We perform experiment on standard benchmarks to demonstrate that our approach has low design overhead. We also conduct security analysis to show that such fingerprints are robust against various attacks.