Secure Multiparty Computation with Identifiable Abort via Vindicating Release

In the dishonest-majority setting, secure multiparty computation (MPC) with identifiable abort (IA) guarantees that honest parties can identify and agree upon at least one cheating party if the protocol does not produce an output. Known MPC constructions with IA rely on generic zero-knowledge proofs, adaptively secure oblivious transfer (OT) protocols, or homomorphic primitives, and thus incur a substantial penalty with respect to protocols that abort without identifiability. We introduce a new, weaker notion of IA called input-revealing IA (IRIA), which can be constructed through selective revealing of committed input values—a technique we call vindicating release. We show that this weaker form of IA can be achieved with small concrete overheads for many interesting protocols in the literature, including the pre-processing protocols needed for several state-of-the-art MPC protocols. We next show how to assemble these IRIA components into an MPC protocol for any functionality with standard IA. Such a realization differs minimally in terms of cost, techniques, and analysis from the equivalent realization that lacks identifiability, e.g., our total bandwidth overhead incurred is less than 2x, which is an asymptotic improvement over prior work on IA. On a practical level, we apply our techniques to the problem of threshold ECDSA, and show that the resulting protocol with standard IA is concretely efficient. On a theoretical level, we present a compiler that transforms any secure protocol into one with standard IA assuming only a variant of statically-corruptable ideal OT.