Paper 2022/290

Universally Composable Sigma-protocols in the Global Random-Oracle Model

Anna Lysyanskaya and Leah Namisa Rosenbloom

Abstract

Numerous cryptographic applications require efficient non-interactive zero-knowledge proofs of knowledge (NIZK PoK) as a building block. Typically they rely on the Fiat-Shamir heuristic to do so, as security in the random-oracle model is considered good enough in practice. However, there is a troubling disconnect between the stand-alone security of such a protocol and its security as part of a larger, more complex system where several protocols may be running at the same time. Provable security in the universal composition (UC) model of Canetti is the best guarantee that nothing will go wrong when a system is part of a larger whole. In this paper, we show how to achieve efficient UC-secure NIZK PoK in the global random-oracle model of Canetti, Jain, and Scafuro.