SDR-PUF: Sequence-Dependent Reconfigurable SRAM PUF with an Exponential CRP Space
Kailash Prasad, Neel Shah, Jinay Dagli, Joycee Mekie · 2024
Physical unclonable functions (PUFs) based on static random access memory (SRAM) are essential in security applications, generating unique challenge-response pairs (CRPs) from manufacturing randomness. These CRPs serve as a foundational element in cryptographic systems, ensuring device authenticity. Two major proposed SRAM PUFs are sequence-dependent and reconfigurable SRAM PUFs. Sequence-dependent SRAM PUFs produce a limited range of CRPs, while reconfigurable SRAM PUFs face a similar limitation, even though individual cells can have a considerable CRP space. The single cell in reconfigurable designs also adds to area consumption. Consequently, both types are classified as weak PUFs. To address these challenges, we introduce a novel approach, SDR-PUF, that combines sequence-dependence and reconfigurability in SRAM PUFs. This approach assigns a unique challenge to each column in the PUF array, diversifying the CRP space exponentially. Notably, the PUF design enhances security without a significant increase in area. We implemented an SDR-PUF array of size $8 \times 8$ in CMOS 28nm to assess our method’s efficacy. The results were promising: our design produced a vast number of unique CRPs, $9. 12 \times 10^{70}$, for a set of 32-bit challenges with a sequence length of 5. Furthermore, our design achieved a high throughput of $7.6 {Gbps} $ at 0.9 V and consumes $0. 14 pJ$ energy per bit at 0.9 V for a sequence length of 5, showcasing its efficiency with a nominal native bit error rate and a high inter-hamming distance.