New constructions of efficient simulation-sound commitments using encryption and their applications

Abstract

Simulation-sound trap-door commitment (SSTC) schemes are an essential ingredient for making non-malleable and universally composable protocols. In previous work, the SSTC schemes and their variants are all constructed in the same framework based on digital signatures. In this paper, we provide new constructions of SSTC schemes using encryption, which is somewhat surprising, because of the tight relationship between SSTC and digital signature schemes. Although our constructions require a few rounds of interactions between a committer and a receiver and the notion of public-key encryption could be stronger than digital signature, the resulting instantiations are much more efficient than these based on digital signature schemes. In particular, we present an efficient SSTC scheme under the CDH assumption in the bilinear groups, with a tight security reduction and short public key parameters, and the first efficient SSTC scheme under the factoring assumption. Our interactive SSTC schemes inherit properties of the non-interactive version of SSTC schemes to construct non-malleable and universally composable protocols. © 2012 Springer-Verlag.