Paper 2024/1626

Faster Proofs and VRFs from Isogenies

Abstract

We improve recent generic proof systems for isogeny knowledge by Cong, Lai, Levin [26] based on circuit satisfiability, by using radical isogeny descriptions [19, 20] to prove a path in the underlying isogeny graph. We then present a new generic construction for a verifiable random function (VRF) based on a one-more type hardness assumption and zero-knowledge proofs. We argue that isogenies fit the constraints of our construction and instantiate the VRF with a CGL walk [22] and our new proofs. As a different contribution, we also propose a new VRF in the effective group action description of isogenies from [1]. Our protocol takes a novel approach based on the polynomial-in-the-exponent technique first described in [36], but without the need of a trusted setup or heavy preprocessing. We compare our protocols to the current state-of-the-art isogeny VRFs by Leroux [53] and Lai [52], with a particular emphasis on computational efficiency.