Concealable and Field‐Free Physical Unclonable Function Based on Voltage‐Controlled Magnetic Tunnel Junctions

ABSTRACT Physical unclonable functions (PUFs) leverage intrinsic stochastic variations of physical properties to generate secure cryptographic keys. Magnetic random‐access memory (MRAM) is a strong candidate for PUF implementations due to its high density, reliability, and complementary‐metal‐oxide‐semiconductor (CMOS) compatibility. However, MRAM‐PUFs reported to date remain vulnerable to adversarial attacks such as side‐channel analysis, highlighting the need for effective concealment strategies. Here, a concealable PUF based on an array of 384 nanoscale perpendicular voltage‐controlled magnetic tunnel junctions (V‐MTJs) is demonstrated. The PUF uses a combination of deterministic and stochastic switching mechanisms for its operation. Variations in the spin transfer torque (STT)‐assisted switching voltage generate unique PUF responses, which are concealed through voltage‐controlled magnetic anisotropy (VCMA)‐induced stochastic switching. Once concealed, it is shown that the PUF responses can be reliably recovered by STT‐assisted deterministic switching. The proposed PUF is magnetic‐field‐free, reliable, and CMOS‐compatible, while exhibiting near‐ideal entropy (0.98) and inter‐Hamming distance (0.508). These results establish a pathway toward secure, scalable MRAM‐PUFs for future hardware security applications.