Feedback Based Supply Voltage Control for Temperature Variation Tolerant PUFs

Physical Unclonable Functions (PUFs) are on-chip identifiers which have found many applications related to security. However, such devices suffer from instability due to time varying noise. Variation in operating temperature is a chief contributor to instability in PUFs. In this paper, we propose two different approaches to increase the stability of the popular ring oscillator PUFs against variations in temperature. The first approach involves using non-feedback based optimization of key circuit topologies including the drive strength of transistors and the stage length of the ring oscillators. However, to improve the stability even further, we propose a feedback based supply voltage control scheme. In this scheme, the supply voltage of the PUF is varied based on the operating temperature of the PUF IC. The optimal supply voltage to be applied to the PUF at each of the operating temperature is identified during the evaluation stage of the PUFs and is stored in the form of a micro-code. Also, a novel architecture supporting this scheme is proposed. Experimental results show that a 40% reduction in hardware is achieved by using this novel architecture.