Two-round secure MPC from Indistinguishability Obfuscation.

One fundamental complexity measure of an MPC protocol is its round complexity. Asharov et al. recently constructed the first three-round protocol for general MPC in the CRS model. Here, we show how to achieve this result with only two rounds. We obtain UC security with abort against static malicious adversaries, and fairness if there is an honest majority. Additionally the communication in our protocol is only proportional to the input and output size of the function being evaluated and independent of its circuit size. Our main tool is indistinguishability obfuscation, for which a candidate construction was recently proposed by Garg et al. The technical tools that we develop in this work also imply virtual black box obfuscation of a new primitive that we call a dynamic point function. This primitive may be of independent interest.