A discrete-logarithm based non-interactive non-malleable commitment scheme with an online knowledge extractor

Abstract

We propose a discrete-logarithm based non-interactive non-malleable commitment scheme with an online knowledge extractor in the random oracle and the public parameter model (need a third party to distribute public parameters to both sender and receiver in advance). Our scheme is statistically-secret computationally-binding. The fundamental technique we employ is the construction of non-interactive zero-knowledge proofs of knowledge with online knowledge extractors from Fiat-Shamir proofs of knowledge for relations with logarithmic challenge length presented by Fischlin in Crypto'05. Compared with previous works, our scheme is practical and the online knowledge extractor is strictly polynomial-time. © 2008 Springer-Verlag Berlin Heidelberg.