A 445F2 leakage-based physically unclonable Function with Lossless Stabilization Through Remapping for IoT Security

Abstract

With the advent of the IoT era, billions of devices are connected to networks, and assuring sufficient security at low cost is a critical concern. Physically Unclonable Functions (PUFs) have drawn increasing attention as key security building blocks for authentication since each PUF circuit has unique challenge response pairs (CRPs). Such uniqueness is achieved by maximizing the effects of process variation using process-sensitive circuits, i.e. PUF cells. Recently reported PUF cell types include cells based on a two-transistor amplifier [1], NAND gate [2], ring oscillator [3], current mirror [4], back-to-back connected inverters [5], and inverter [6]. Regardless of the variation source, PUFs inevitably include CRPs that respond inconsistently when the process variation of the compared element in the CRP is small compared to noise. For example, if the output of a two-transistor amplifier in [1] is near the switching threshold, the output can be inconsistent, resulting in bit error and an unstable CRP. Thus, efforts have focused on stabilizing unstable CRPs. The most straightforward stabilization scheme is temporal majority voting (TMV) [1,5], but the improvement in bit error rate (BER) and stability is limited since it does not directly address the instability of a given CRP. Trimming [2,3,5,6], another widely used approach, improves BER/stability by discarding unstable CRPs. However, stability evaluation is not very accurate, so the number of discarded CRPs can be significant (up to 30% in [3]), increasing the required silicon area for additional CRP generation and making it prohibitive for cost-sensitive IoT applications. This is especially true for weak PUFs. In this paper, a leakage-based PUF that allows lossless stabilization through remapping of unstable PUF cell pairs is presented. BER and stability comparable to, or better than, trimming stabilization method are achieved without discarding CRPs.