Low Cost Constant Round MPC Combining BMR and Oblivious Transfer
Carmit Hazay, Peter Schöll, Eduardo Soria-Vázquez
Abstract
In this work, we present two new actively secure, constant-round multi-party computation (MPC) protocols with security against all-but-one corruptions. Our protocols both start with an actively secure MPC protocol, which may have linear round complexity in the depth of the circuit, and compile it into a constant-round protocol based on garbled circuits, with very low overhead. In both approaches, the underlying secret-sharing-based protocol is only used for one actively secure $$\mathbb {F}_2$$ multiplication per AND gate. An interesting consequence of this is that, with current techniques, constant-round MPC for binary circuits is not much more expensive than practical, non-constant-round protocols. We demonstrate the practicality of our second protocol with an implementation and perform experiments with up to 9 parties securely computing the AES and SHA-256 circuits. Our running times improve upon the best possible performance with previous protocols in this setting by 60 times.