Three-Round Secure Multiparty Computation from Black-Box Two-Round Oblivious Transfer

We give constructions of three-round secure multiparty computation (MPC) protocols for general functions that make black-box use of a two-round oblivious transfer. For the case of semi-honest adversaries, we make use of a two-round, semi-honest secure oblivious transfer in the plain model. This resolves the round-complexity of black-box (semi-honest) MPC protocols from minimal assumptions and answers an open question of Applebaum et al. (ITCS 2020). For the case of malicious adversaries, we make use of a two-round maliciously-secure oblivious transfer in the common random/reference string model that satisfies a (mild) variant of adaptive security for the receiver.