Optimizing and Implementing Fischlin's Transform for UC-Secure Zero-Knowledge

ePrint Report: Optimizing and Implementing Fischlin's Transform for UC-Secure Zero-Knowledge

Yi-Hsiu Chen, Yehuda Lindell

Fischlin's transform (CRYPTO 2005) is an alternative to the Fiat-Shamir transform that enables straight-line extraction when proving knowledge. In this work we focus on the problem of using the Fischlin transform to construct UC-secure zero-knowledge from Sigma protocols, since UC security -- that guarantees security under general concurrent composition -- requires straight-line (non-rewinding) simulators. We provide a slightly simplified transform that is much easier to understand, …

chen crypto eprint report extraction fiat focus knowledge line problem protocols report sigma transform work