Efficient Private Information Retrieval Protocol with Homomorphically Computing Univariate Polynomials

Wenju Xu,Yange Chen,Yupu Hu,Rongxing Lu,Baocang Wang,Quanbo Qu,Leandros Maglaras

doi:10.1155/2021/5553256

Abstract

Private information retrieval (PIR) protocol is a powerful cryptographic tool and has received considerable attention in recent years as it can not only help users to retrieve the needed data from database servers but also protect them from being known by the servers. Although many PIR protocols have been proposed, it remains an open problem to design an efficient PIR protocol whose communication overhead is irrelevant to the database sizeN. In this paper, to answer this open problem, we present a new communication-efficient PIR protocol based on our proposed single-ciphertext fully homomorphic encryption (FHE) scheme, which supports unlimited computations with single variable over a single ciphertext even without access to the secret key. Specifically, our proposed PIR protocol is characterized by combining our single-ciphertext FHE with Lagrange interpolating polynomial technique to achieve better communication efficiency. Security analyses show that the proposed PIR protocol can efficiently protect the privacy of the user and the data in the database. In addition, both theoretical analyses and experimental evaluations are conducted, and the results indicate that our proposed PIR protocol is also more efficient and practical than previously reported ones. To the best of our knowledge, our proposed protocol is the first PIR protocol achievingO1communication efficiency on the user side, irrelevant to the database sizeN.

Highlights

Private information retrieval (PIR) protocol [1] is a cryptographic primitive run between database servers and a user.e salient feature of PIR is that it ensures the user can obtain some data from the database servers, while the database servers cannot learn anything about the queries of the user
Considering that there are continuous interactions with multiservers at the price of communication costs for the user, many research studies have been focused on the singleserver PIR protocol that is composed of only one database server and one query user [1,2,3,4,5,6,7]
To address the above open problem, we propose a new fully homomorphic encryption (FHE) scheme with special properties and utilize it to design a new single-server PIR protocol with O(1) communication efficiency for any user

Summary

Introduction

E salient feature of PIR is that it ensures the user can obtain some data from the database servers, while the database servers cannot learn anything about the queries of the user. A trivial solution for the user is to download all the data from the database servers and obtain the data he wants to ask at any time. This solution wastes plenty of time and storage space for the user since the database servers usually store a huge volume of items. In 1997, the first single-server PIR protocol was proposed by Kushilevitz and Ostrovsky [2].

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Methods

Conclusion