Practical and provably-secure commitment schemes from collision-free hashing

Abstract

We present a very practical string-commitment scheme which is provably secure based solely on collision-free hashing. Our scheme enables a computationally bounded party to commit strings to an unbounded one, and is optimal (within a small constant factor) in terms of interaction, communication, and computation. Our result also proves that constant round statistical zero-knowledge arguments and constant-round computational zero-knowledge proofs for NP exist based on the existence of collision-free hash functions.