A 266F2 Ultra Stable Differential NOR-Structured Physically Unclonable Function With < 6×10-9 Bit Error Rate Through Efficient Redundancy Strategy

Abstract

This brief presents a NOR-structured physically unclonable function (PUF) tailored for low-cost Internet of Things (IoT) applications. The proposed NOR-structured PUF utilizes a single minimum-sized differential NMOS pair, capitalizing on threshold-voltage mismatch as the entropy source. Fabricated in 65nm CMOS, the basic PUF cell is a $58F^{2}$ differential NMOS pair, demonstrating a raw bit error rate (BER) of 0.31%. To further enhance the stability and achieve an ultra-low BER, we introduce an area-efficient redundancy strategy. By incorporating 4x redundancy cells ( $266F^{2}$ in total), the prototype chip achieves an ultra-low BER (zero error in 20M bits), over a wide temperature range (−20 to 125°C) and supply voltage variations (0.8 to 1.2V). The core energy consumption is only 63fJ/bit, offering a low-cost and highly stable solution for IoT applications.