Paper 2020/494

Improved Black-Box Constructions of Composable Secure Computation

Rohit Chatterjee, Xiao Liang, and Omkant Pandey

Abstract

We close the gap between black-box and non-black-box constructions of $\mathit{composable}$ secure multiparty computation in the plain model under the $\mathit{minimal}$ assumption of semi-honest oblivious transfer. The notion of protocol composition we target is $\mathit{angel}\mathit{\text{-}}\mathit{based}$ security, or more precisely, security with super-polynomial helpers. In this notion, both the simulator and the adversary are given access to an oracle called an $\mathit{angel}$ that can perform some predefined super-polynomial time task. Angel-based security maintains the attractive properties of the universal composition framework while providing meaningful security guarantees in complex environments without having to trust anyone. Angel-based security can be achieved using non-black-box constructions in $$ rounds where $$ is the round-complexity of the semi-honest oblivious transfer. However, currently, the best known $$ constructions under the same assumption require $$ rounds. If $$ is a constant, the gap between non-black-box and black-box constructions can be a multiplicative factor $$. We close this gap by presenting a $$-round black-box construction. We achieve this result by constructing constant-round 1-1 CCA-secure commitments assuming only black-box access to one-way functions.

Note: Full version version of the original publication.