A 20F 2/Bit Current-Integration-Based Differential NAND -Structured PUF for Stable and V /T V ariation-Tolerant Low-Cost IoT Security

Abstract

A current-integration-based differential NAND - structured physically unclonable function (PUF) with 20F 2 area per bit is proposed for low-cost IoT security. Current integration scheme with a capacitor is adopted to generate a response bit by comparing the delay of capacitor charging through pair of selected MOSFET transistors. For area-efficient implemen- tation, minimum-sized MOSFETs are selected from NAND -flash- like array structure. By operating selected MOSFET pairs in moderate inversion mode, higher sensitivity to threshold volt- age ( Vth) variation, and hence more stable response genera- tion, is achieved while keeping it faster than weak inversion operation. A stabilization scheme based on current integration is proposed by discarding or remapping the transistor pairs that generate small charging delay difference. The proposed current-integration-based differential NAND -structured PUF (CI NAND -PUF) achieved high V/T variation tolerance of 0.145%/0.1 V and 0.120%/10 ◦C while limiting 20F 2/bit area for 1-bit random response generation. With the proposed stabiliza- tion scheme, up to 11 × and 7.7× BER improvement is achieved for trimming and remapping, respectively.