Concealable and Bit Error-Free Breakdown-Based Physical Unclonable Functions Using Magnetic Tunnel Junctions

This work is the first to demonstrate a concealable breakdown-based physically unclonable function (PUF) using magnetic tunnel junctions (MTJs), referred to as MBD-PUF, using a fabricated 64×64 2T2R MRAM macro. PUF responses are formed by pulse-controlled breakdown with a target probability, where breakdown (BD) and non-breakdown (n-BD) cells represent '1' and '0', respectively. By leveraging the memory state of n-BD cells, the response can be concealed to enhance security. The responses exhibit near-ideal randomness metrics and maintain bit-error-free readout under 10k repeated accesses and 1k conceal-reveal cycles, both at 125^oC. Device-level characterization was performed to understand BD-related behaviors, including soft BD and resistance shifts. A strong PUF architecture using these responses as entropy sources is also proposed, with ML- and rank-based attack resistance. The design is compatible with commercial MRAM/OTP platforms, enabling secure and scalable hardware integration.