Accelerating Oblivious Transfer with Batch Multi-exponentiation

More and more people use smart end devices to retrieve digital items and purchase on the Internet. Oblivious transfer (OT) is a fundamental tool to protect user privacy in such applications. Most existing works devote to improving the communication performance of OT protocols; few work has been done to improve the computation efficiency. Modular exponentiation is the most frequent operation in OT protocols. It is known that the computation cost of any OT protocol must be linear with the database size; speeding up the exponentiations is critical for OT protocols to be deployed in practice. To this end, we investigate batch multi-exponentiation algorithms and propose two new algorithms. Then we apply our batch multi-exponentiation algorithms to acceleration of OT protocols. Our approach is especially useful for the k-out-n OT. We also exploit the algorithm to speed up simultaneous execution of 1-out-n OT protocols which we called batch OT. We conduct a series of experiments and the experimental results show that our approach is effective and can significantly accelerate OT protocols.