I. Introduction
Oxide-based RRAM is an emerging nonvolatile memory (NVM) candidate [1]. However, it has a large variability in resistance distribution because of the stochastic switching mechanism involving oxygen vacancies’ generation and migration, which adds significant design challenges for NVM applications. On the other hand, hardware security applications generally embrace truly random variations. Here we leverage RRAM’s variability to design a Physical Unclonable Function (PUF). PUF has been used for device authentication and key generation [2]. PUF has two primary requirements that need to be satisfied: uniqueness and reliability [3]. Uniqueness means that the responses resulting from evaluating the same challenge on different PUF instances should be different, i.e., the inter-Hamming distance (HD) of the response bits should be close to 50%. Reliability means that responses resulting from evaluating the same challenge on the same PUF instance should be similar, i.e., the intra-Hamming distance (HD) between the response bits should be close to 0%.