# Location Privacy in Cognitive Radios with Multi-Server Private Information Retrieval

## TL;DR

This paper proposes a multi-server PIR approach to enhance location privacy for both primary and secondary users in spectrum database-based cognitive radio networks, achieving high efficiency and information-theoretic privacy.

## Contribution

It introduces the novel use of multi-server PIR in CRNs, leveraging synchronized databases to provide optimal privacy with reduced overhead.

## Key findings

- Multi-server PIR achieves high efficiency in CRNs.
- Provides information-theoretic privacy for PUs and SUs.
- Validated through analytical and empirical evaluations.

## Abstract

Spectrum database-based cognitive radio networks (CRNs) have become the de facto approach for enabling unlicensed secondary users (SUs) to identify spectrum vacancies in channels owned by licensed primary users (PUs). Despite its merits, the use of spectrum databases incurs privacy concerns for both SUs and PUs. Single-server private information retrieval (PIR) has been used as the main tool to address this problem. However, such techniques incur extremely large communication and computation overheads while offering only computational privacy. Besides, some of these PIR protocols have been broken. In this paper, we show that it is possible to achieve high efficiency and (information-theoretic) privacy for both PUs and SUs in database-driven CRN with multi-server PIR. Our key observation is that, by design, database-driven CRNs comprise multiple databases that are required, by the Federal Communications Commission, to synchronize their records. To the best of our knowledge, we are the first to exploit this observation to harness multi-server PIR technology to guarantee an optimal privacy for both SUs and PUs, thanks to the unique properties of database-driven CRN . We showed, analytically and empirically with deployments on actual cloud systems, that multi-server PIR is an ideal tool to provide efficient location privacy in database-driven CRN.