Bias PUF based Secure Scan Chain Design

Abstract

Scan chains increase the testability but decrease the security. Attackers may use scan chains to steal key data. To prevent attackers from controlling and observing the data of scan cells, this paper proposes a novel Bias Physical Unclonable Function (PUF) based secure scan chain design. The Bias PUF, which is driven by low speed clock and produces response bit 1 in rare challenges, is proposed. For attackers, without right challenges, data cannot be shifted in or shifted out from scan chain. Moreover, to reduce the negative effect on test time, multiplexers are designed to control the data flow along the scan chain. Experimental results and analysis show that, the proposed scan chain design can resist existing attacks without sacrificing the testability. In comparison with previous works, the hardware overhead is less and the test time is shorter.