Ultra-Low Power Physical Unclonable Function with Nonlinear Fixed-Resistance Crossbar Circuits

The proliferation of networked mobile devices and smart gadgets in the IoT landscape has accelerated the demand for lightweight, low power and operationally compatible cryptographic solutions. As a result, emergent hardware-intrinsic security architecture must demonstrate manufacturability, power efficiency and platform compatibility, in addition to robust security performance. Here we present a novel design of physical unclonable function, called VRPUF, and prototype it using unformed 4K-ReRAM passive crossbar circuits fabricated with a CMOS-compatible process, suitable for the back-end-of-line (BEOL) integration. The architecture utilizes intrinsic process variations in crossbar circuits, manifested as variations in device I-V nonlinearities and the leakage currents, and allows for extremely large (~10
²⁵
) number of challenge-response pairs (CRPs). The VRPUF design does not require forming/programming crosspoint devices, which simplifies peripheral circuits, leading to ~ 4× better density compared to the architectures which rely on switching the states of ReRAM devices. Moreover, uniform I-Vs of the virgin-state devices, coupled with lower conductance and stronger static nonlinearity, allow for ~100× improvement in power consumption and more robust security metrics. The intrinsic reliability of VRPUF primitives is also ~4× better compared to CMOS architectures, which can be further improved via selective de-enrolling of worst-case CRPs prior to deployment.