A Weak-PUF-Assisted Strong PUF with Inherent Security Using Metastability Implemented on FPGAs

Physical unclonable functions (PUFs) are emerging as highly promising lightweight hardware security primitives that offer novel information security solutions. PUFs capitalize on the intrinsic physical variations within circuits to generate unpredictable responses. Nevertheless, diverse PUF types often encounter difficulties in concurrently fulfilling multiple performance requisites. As is well known, strong PUFs possess significantly larger challenge–response pair (CRP) set sizes. However, they are vulnerable to machine learning (ML) attacks. Conversely, weak PUFs generate responses with superior randomness, yet their CRP sets are inadequate to satisfy the demands of practical applications. This paper presents a newly devised double-latch PUF (DL-PUF) to address this issue. This design significantly enhances both the CRP set size and security performance. The available CRPs of the DL-PUF design can reach up to 264, and its robust security features are also demonstrated in this paper. We have implemented this design on twelve 45 nm Xilinx Spartan 6 XC6SLX25 FPGAs. The experimental results indicate that our proposed DL-PUF performs well in terms of reliability, uniqueness, uniformity, and randomness. Additionally, three machine learning algorithms were employed to conduct comprehensive tests on the DL-PUF. The results reveal its excellent resilience against machine learning attacks.