Practical two-party computation based on the conditional gate

Abstract

We present new results in the framework of secure multi-party computation based on homomorphic threshold cryptosystems. We introduce the conditional gate as a special type of multiplication gate that can be realized in a surprisingly simple and efficient way using just standard homomorphic threshold ElGamal encryption. As addition gates are essentially for free, the conditional gate not only allows for building a circuit for any function, but actually yields efficient circuits for a wide range of tasks. © International Association for Cryptologic Research 2004.