SSTKR: Secure and Testable Scan Design through Test Key Randomization

Abstract

Scan test is the standard method, practiced by industry, that has consistently provided high fault coverage due to high controllability and high observability. The scan chain allows to control and observe the internal signals of a chip. However, this property also facilitates hackers to use scan architecture as a means to breach chip security. This paper addresses this issue by proposing a new method called Secure and testable Scan design through Test Key Randomization(SSTKR). SSTKR is a key based method to prevent hackers from stealing secret information. Linear Feedback Shift Register (LFSR) is used to generate authentication keys to be embedded in test vectors. Unique key is used for every test vector which prevents scan based side channel attacks effectively. Any attempt to steal secret information will lead to a randomized response. SSTKR has very low area and test time overhead without performance penalty. Our approach also facilitates in-field test of the chip.