Multi-value Private Information Retrieval using Homomorphic Encryption

Abstract

Private information retrieval (PIR) is a privacy protection that allows users to retrieve information from a database without revealing any information about the retrieved data to the server. Since the pioneering work of Chor et al. (FOCS ‘95) and of Kushilevitz and Ostrovsky (FOCS ‘97), PIR has been extensively studied (especially the single database setting) in the past two decades. However, most protocols only allow users to retrieve only one data at a time, which leads to high communication costs. To solve this issue, this work proposes a multi-value private information retrieval protocol using group homomorphic encryption, which allows users to retrieve multiple values at a time. We compared our work with that of Ostrovsky and Skeith (PKC ‘07) and show that retrieving multiple data at a time significantly can significantly reduces communication costs. Furthermore, we provide rigorous proof that if the underlying group homomorphic encryption is secure, then no attacker can know what data the user has retrieved.