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.

Reconfigurable Scan Networks (RSNs) are a powerful tool for testing and maintenance of embedded systems, since they allow for flexible access to on-chip instrumentation such as built-in self-test and debug modules. RSNs, however, can be also exploited by malicious users as a side-channel in order to gain information about sensitive data or intellectual property and to recover secret keys. Hence, implementing appropriate counter-measures to secure the access to and data integrity of embedded instrumentation is of high importance. In this paper we present a novel hardware and software combined approach to ensure data privacy in IEEE Std 1687 (IJTAG) RSNs. To do so, both a secure IJTAG compliant plug-and-play instrument wrapper and a versatile software toolchain are introduced. The wrapper demonstrates the necessary architectural adaptations required when using a lightweight stream cipher, whereas the software toolchain provides a seamless integration of the testing workflow with stream cipher. The applicability of the method is demonstrated by an FPGA-based implementation. We report on the performance of the developed instrument wrapper, which is empirically shown to have only a small impact on the workflow in terms of hardware overhead, operational costs and test time overhead.

The accessibility of on-chip embedded infrastructure for test, reconfiguration, or debug poses a serious security problem. Access mechanisms based on IEEE Std 1149.1 (JTAG), and especially reconfigurable scan networks (RSNs), as allowed by IEEE Std 1500, IEEE Std 1149.1-2013, and IEEE Std 1687 (IJTAG), require special care in the design and development. This work studies the threats to trustworthy data transmission in RSNs posed by untrusted components within the RSN and external interfaces. We propose a novel scan pattern generation method that finds trustworthy access sequences to prevent sniffing and spoofing of transmitted data in the RSN. For insecure RSNs, for which such accesses do not exist, we present an automated transformation that improves the security and trustworthiness while preserving the accessibility to attached instruments. The area overhead is reduced based on results from trustworthy access pattern generation. As a result, sensitive data is not exposed to untrusted components in the RSN, and compromised data cannot be injected during trustworthy accesses.