Reconfigurable physical unclonable cryptographic primitives based on current-induced nanomagnets switching

Abstract

Hardware security primitives that preserve secrets are playing a crucial role in the Internet-of-Things (IoT) era. Existing physical unclonable function (PUF) instantiations, exploiting static randomness, generate challenge-response pairings (CRPs) to produce unique security keys that can be used to authenticate devices linked to the IoT. Reconfigurable PUFs (RPUFs) with dynamically refreshable CRPs can enhance the security and robustness of conventional PUFs. The in-plane current-driven perpendicular polarized nanomagnet switching via spin-orbit torque (SOT) possesses great potential for application to memory and logic, as the write-current path is separate from the read-current path, which naturally resolves the write-read interference. However, the stochastic switching of perpendicular magnetization, without an additional symmetry-breaking field, would significantly hinder the technological viability of commercial implementations. Here, we report an initialization-free physical RPUF implemented by SOT-induced stochastic switching of perpendicularly magnetized Ta/CoFeB/MgO nanodevices. Using a 15 × 15 nanomagnet array, we experimentally demonstrate a security primitive that offers a near-ideal 50% uniqueness over 100 reconfiguration cycles, as well as a low correlation coefficient between every two reconfiguration cycles. Our results show that current-induced nanomagnets switching paves the way for developing highly reliable and energy-efficient reconfigurable cryptographic primitives with a smaller footprint.