Paper 2022/803

Lattice-based Interactive Zero-Knowledge without Aborts

Abstract

Interactive zero-knowledge systems are a very important cryptographic primitive, used in many applications, especially when non-transferability is desired. In the setting of lattice-based cryptography, the currently most efficient interactive zero-knowledge systems employ the technique of rejection sampling, which implies that the interaction does not always finish correctly in the first execution; the whole interaction must be re-run until abort does not happen. While aborts and repetitions are acceptable in theory, in some practical applications of such interactive systems it is desirable to avoid re-runs, for usability reasons. In this work, we present a generic transformation that departs from an interactive zero-knowledge system (maybe with aborts) and obtains a 3-moves zero-knowledge system (without aborts). The transformation combines the well-known Fiat-Shamir technique with a couple of initially exchanged messages. %, needed to get the (honest-verifier) zero-knowledge property. The resulting 3-moves system enjoys (honest-verifier) zero-knowledge and soundness, in the random oracle model. We finish the work by showing some practical scenarios where our transformation can be useful.