Highly Secure Physically Unclonable Cryptographic Primitives Based on Interfacial Magnetic Anisotropy

Information security is of great importance for the approaching Internet of things (IoT) era. Physically unclonable functions (PUFs) have been intensively studied for information security. However, silicon PUFs are vulnerable to hazards such as modeling and side-channel attacks. Here we demonstrate a magnetic analogue PUF based on perpendicularly magnetized Ta/CoFeB/MgO heterostructures. The perpendicular magnetic anisotropy originates from the CoFeB/MgO interface, which is sensitive to the subnanometer variation of MgO thickness within a certain range (0.6-1.3 nm). When the MgO layer is thinned, a thickness variation resulting from ion milling nonuniformity induces unclonable random distributions of easy-axis magnetization orientations in heterostructures. The analogue PUF can provide a much larger key size than a conventional binary-bit counterpart. Moreover, after the thinning process, the unique easy-axis magnetization orientation in each single device was formed, which can avoid setting random states to realize low power consumption and high-density integration. This magnetic PUF is a promising innovative primitive for secret key generation and storage with high security in the IoT era.