Non-Interactive Secure Computation Based on Cut-and-Choose.

In recent years, secure two-party computation (2PC) has been demonstrated to be feasible in practice. However, all efficient general-computation 2PC protocols require multiple rounds of interaction between the two players. This property restricts 2PC to be only relevant to scenarios where both players can be simultaneously online, and where communication latency is not an issue. This work considers the model of 2PC with a single round of interaction, called Non-Interactive Secure Computation (NISC). In addition to the non-interaction property, we also consider a flavor of NISC that allows reusing the first message for many different 2PC invocations, possibly with different players acting as the player who sends the second message, similar to a public-key encryption where a single public-key can be used to encrypt many different messages. We present a NISC protocol that is based on the cut-and-choose paradigm of Lindell and Pinkas (Eurocrypt 2007). This protocol achieves concrete efficiency similar to that of best multi-round 2PC protocols based on the cut-and-choose paradigm. The protocol requires only t garbled circuits for achieving cheating probability of 2-t, similar to the recent result of Lindell (Crypto 2013), but only needs a single round of interaction. To validate the efficiency of our protocol, we provide a prototype implementation of it and show experiments that confirm its competitiveness with that of the best multi-round 2PC protocols. This is the first prototype implementation of an efficient NISC protocol. In addition to our NISC protocol, we introduce a new encoding technique that significantly reduces communication in the NISC setting. We further show how our NISC protocol can be improved in the multi-round setting, resulting in a highly efficient constant-round 2PC that is also suitable for pipelined implementation.