Selected Bit-Line Current PUF: Implementation of Hardware Security Primitive Based on a Memristor Crossbar Array

In this paper, a physical unclonable function (PUF), a type of hardware security device, is proposed to overcome the limitations of existing security schemes. A 32\times 32 crossbar array using TiOx/Al2O3- based memristors was fabricated, and electrical characteristics including its set voltage distribution were analyzed. The memristor switching characteristics model is described in a simplified space-charge-limited current (SCLC) regime. Based on this I-V model, selected bit-line current PUFs (SBC-PUFs) were designed with 32\times 32 , 64\times 64 , and 128\times 128 crossbar arrays. The entropy source of these PUFs is the set voltage deviation in the fabricated memristors. Due to these characteristics, the SBC-PUF can exploit the broad resistance distribution near the switching region, including the internal resistance distributions of the high resistance state (HRS) and low resistance state (LRS). The SBC-PUF performance was evaluated for randomness/uniformity, correctness/reliability, and uniqueness by calculating the Hamming weight and intra/inter Hamming distance of challenge-response pairs (CRPs). The designed structure demonstrates high-security performance due to the high value of these indicators and the large number of CRPs. Furthermore, the devised PUF has a higher prediction error rate than arbiter PUF in machine learning attacks. This study verified that the SBC-PUF using the memristor of the crossbar array structure is safe enough to be used for hardware security.