A Homogeneous, Reconfigurable, and Efficient Implementation of PUF in 3-D Selector-Free RRAM

Hardware encryption primitives such as physical unclonable functions (PUFs) are used in power and cost limited Internet of Things (IoT) and computing on edge devices. Resistive random access memory (RRAM) PUF is proposed as an alternative to CMOS one. But due to the existence of transistors as selectors, it still shares the drawbacks of CMOS PUF. In this work, a homogeneous and efficient PUF was constructed out of 3-D selector-free RRAM. It is immune to ray attack and fault injection and features low power, thanks to the absence of transistors and high-resistance states of the RRAM cells. The inter-and intra-Hamming distances (HDs) are measured to be 50.02% and 0%, respectively, which well validates its uniqueness and reliability. Experimental results show that the proposed PUF can be operated with a low energy consumption of 144 fJ/bit, and a compact bit-cell area of 16 text F2/bit. The digital values in the cells can maintain for over 100 h at 85 °C, which is equivalent to 24 years under 40 °C. Besides, given that the selector-free structure renders the PUF instance homogeneous, the PUF instance has enhanced security performance against radiation.