Highly Efficient and Re-executable Private Function Evaluation with Linear Complexity

Abstract

Private function evaluation aims to securely compute a function f(x_1,…, x_n) without leaking any information other than what is revealed by the output, where f is a private input of one of the parties (say Party1) and x_i is a private input of the i-th party Party_i. In this work, we propose a novel and secure two-party private function evaluation (2PFE) scheme based on the DDH assumption. Our scheme introduces a reusability feature that significantly improves the state-of-the-art. Accordingly, our scheme has two variants, one is utilized in the initial execution of the function f, and the other is utilized in its subsequent evaluations. To the best of our knowledge, this is the first and most efficient 2PFE scheme that enjoys a reusability feature. Our protocols achieve linear communication and computation complexities and a constant number of rounds which is at most three.