1 Introduction
Silicon physical unclonable functions (PUFs) are security primitives commonly adopted for device identification, authentication, and cryptographic key generation [39]. A PUF exploits the inherent randomness of CMOS technology to generate an output response for a given input challenge. Weak PUFs, which are also called physically obfuscated keys (POKs) [16], have a limited challenge-response pair (CRP) space. In contrast, strong PUFs supply an exponentially large number of CRPs.