Robustly Reusable Fuzzy Extractors in a Post-quantum World

Abstract

We revisit the problem of robustly reusable fuzzy extractors (RRFEs) with post-quantum security. Our main focus is constructions secure in the quantum random oracle model (QROM) that can be built by modifying existing classical ROM constructions. To date, security in the QROM has not been considered in the context of RRFEs. More specifically, we achieve three core contributions. The first is to produce a simple QROM construction of a (non-reusable) robust fuzzy extractor with security bounds that do not depend explicitly on the number of correctable errors t. As Becker (ePrint/2017/493) showed, previous ROM proofs depend heavily on t, preventing their use in certain applications (e.g. to PUFs). Our second contribution is to produce the first RRFE with a security proof in the QROM. The security bounds here also do not depend explicitly on t. Importantly, the construction does not utilise random number generation which can be difficult to achieve on constrained devices in a PUF application. Finally, we suggest optimisations of the only existing post-quantum standard model RRFE capable of correcting a linear number of errors, showing that it is far less efficient than our QROM construction.