Understanding sources of variations in flash memory for physical unclonable functions

This paper provides detailed characterizations of physical sources behind Flash memory based Physical Unclonable Functions (FPUFs). Universal process variations in Flash physical systems are identified and decomposed into layout, intrinsic, stress and bit-wise fluctuation sources. The study shows the understanding of systematic variations and noise sources are essential for improving the security and reliability of FPUFs. Bitwise variations are proven to be originated mainly from random dopant fluctuation, which is indeed truly random and impossible to clone. Overall, this paper provides a theoretical foundation for the security of FPUFs whereas previous PUF studies rely only on experimental evidence for its security and entropy.