Robust RO-PUFs with enhanced challenge-response set

Abstract

Ring Oscillator (RO) Physical Unclonable Functions (PUFs) are one of the best performing PUF types among various structures presented in the literature. The robustness problem of conventional RO-PUFs, that arises due to the noisy nature of ROs, is overcome with the Ordering-Based RO-PUFs presented recently. However, the shortage of usable Challenge-Response Pairs (CRPs) still limits the use of RO-PUFs, especially for authentication protocols in security systems. For a fully secure authentication based on PUF circuits, CRPs should be independent from each other and a full read-out of all CRPs should be infeasible. In conventional RO-PUFs, the number of possible CRPs is very limited and in ordering based RO-PUFs, the CRP concept is not defined at all. In this work, two methods based on RO selection is proposed for generating enhanced CRP set in ordering based RO-PUFs and their performance is analyzed in terms of area efficiency and uniqueness. With the proposed methods, robust, area and power efficient RO-PUFs with a very high number of CRPs are available for use in many security applications.