Paper 2019/1300

Actively Secure Setup for SPDZ

Dragos Rotaru and Nigel P. Smart and Titouan Tanguy and Frederik Vercauteren and Tim Wood

Abstract

We present an actively secure, practical protocol to generate the distributed secret keys needed in the SPDZ offline protocol. The resulting distribution of the public and secret keys is such that the associated SHE `noise' analysis is the same as if the distributed keys were generated by a trusted setup. We implemented the presented protocol for distributed BGV key generation within the SCALE-MAMBE framework. Our method makes use of a new method for creating doubly (or even more) authenticated bits in different MPC engines, which has applications in other areas of MPC-based secure computation. We were able to generate keys for two parties and a plaintext size of 64 bits in less than ten minutes, and approximately half an hour for a 128 bit prime.