Round-Optimal Black-Box Protocol Compilers

We give black-box, round-optimal protocol compilers from semi-honest security to malicious security in the Random Oracle Model (ROM) and in the 1-out-of-2 OT correlations model. We use our compilers to obtain the following results: A two-round, two-party protocol secure against malicious adversaries in the random oracle model making black-box use of a two-round semi-honest secure protocol. Prior to our work, such a result was not known even considering special functionalities such as a two-round oblivious transfer. This result also implies the first constructions of two-round malicious (batch) OT/OLE in the random oracle model based on the black-box use of two-round semi-honest (batch) OT/OLE.A three-round multiparty secure computation protocol in the random oracle model secure against malicious adversaries that is based on the black-box use of two-round semi-honest OT. This protocol matches a known round complexity lower bound due to Applebaum et al. (ITCS’20) and is based on a minimal cryptographic hardness assumption.A two-round, multiparty secure computation protocol in the 1-out-of-2 OT correlations model that is secure against malicious adversaries and makes black-box use of cryptography. This gives new round-optimal protocols for computing arithmetic branching programs that are statistically secure and makes black-box use of the underlying field. As a contribution of independent interest, we provide a new variant of the IPS compiler (Ishai, Prabhakaran and Sahai, Crypto 2008) in the two-round setting, where we relax requirements on the IPS “inner protocol” by strengthening the “outer protocol”.