Method for faster secure multiparty inner product with spdz

Abstract

A method for implementing a secure multiparty inner product computation between two parties using an SPDZ protocol involves having a first party and a second party compute, for i=1, . . . , k, a vector (I)=(II) based on a vector (x={x, . . . , x}), and a vector (w={W, W}), respectively, where (I)=(XX) (III)=WW, N is the total number of elements in the vectors k=N/2. The vectors (I), and (III) are securely shared between the parties. The parties then jointly compute SPDZ protocol Add([w], [x]) and Add([w], [x]) to determine shares [w+x] and [w+x] respectively, and then compute, for i=1, . . . , k, inner product shares [d] by performing SPDZ protocol Mult([w+x], [w+x]). SPDZ protocol ([Add d], . . . , [d], -(IV), . . . , -(V), -(VI), -, (VII)) is then performed to determine the inner product.