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.

Nanoscale Vector Magnetic Sensing with Current‐Driven Stochastic Nanomagnet

“…This stochastic switching feature has been confirmed and used for nanomagnetic logic and true random number generators in previous work. [17,18] Besides H z , a z-component effective field H z,eff generated by the IP current with a collinear magnetic field through SOT can also determine P up , making it feasible to detect an IP field with the proposed sensor. H z,eff is written as a function of the current density along the x-(or y-) direction J x(y) and the normalized magnetization m x(y) caused by its corresponding collinear magnetic field H x(y) :…”

Reconfigurable Multilevel Optical PUF by Spatiotemporally Programmed Crystallization of Supersaturated Solution

“…[36] At the same time, these PUFs may not be an optimum solution as an ephemeral key for shortterm credentials, since the conventional PUF does not allow reconfiguration of the original cryptographic keys and this leads to the disposal of a PUF as waste after a corresponding session. [37][38][39] As a potential solution to these problems, we developed a reconfigurable optical PUF based on controlled crystallization of supersaturated solution that provides multilevel cryptographic keys to enable a reusable and more time-efficient authentication system. For a representative supersaturated solution, sodium acetate is selected, which is commonly used in industry to store solar energy [40] and also in heating pads for everyday use.…”

“…[ 36 ] At the same time, these PUFs may not be an optimum solution as an ephemeral key for short‐term credentials, since the conventional PUF does not allow reconfiguration of the original cryptographic keys and this leads to the disposal of a PUF as waste after a corresponding session. [ 37–39 ]…”

Spintronic Physical Unclonable Functions Based on Field‐Free Spin–Orbit‐Torque Switching

“…Spintronics that utilizes electron spin in solid‐state devices [ 22,23 ] has also been employed for hardware security primitives. [ 24–30 ] For example, the spintronic PUFs utilize the distribution of the magnetization switching current or perpendicular magnetic anisotropy as the entropy source to create unique CRPs. [ 26,27 ] Like other spin‐based devices, spintronic PUFs can have the benefits of low power consumption, non‐volatility and high endurance.…”

“…[ 26,27 ] Like other spin‐based devices, spintronic PUFs can have the benefits of low power consumption, non‐volatility and high endurance. [ 31,32 ] Note that some spintronic PUFs are capable of generating digital outputs [ 25,29,30 ] using discrete up and down magnetizations of perpendicularly magnetized ferromagnets. However, spintronic PUFs are vulnerable to magnetic fields; their unique patterns can be modified when exposed to an external magnetic field.…”