# Oblivious Location-Based Service Query

## TL;DR

This paper introduces an efficient privacy-preserving location-based service query scheme that eliminates the need for a semi-trusted third party and reduces query costs to constant time, enhancing privacy and efficiency.

## Contribution

The paper proposes a novel OLBSQ scheme that removes the semi-trusted third party requirement and achieves constant computation and communication costs for queries.

## Key findings

- Query costs are constant, independent of queried area size.
- User location remains private during service queries.
- Service provider learns only the size of the query, not the exact location.

## Abstract

Privacy-preserving location-base services (LBS) have been proposed to protect users' location privacy. However, there are still some problems in existing schemes: (1) a semi-trusted third party (TTP) is required; or (2) both the computation cost and communication cost to generate a query are linear in the size of the queried area. In this paper, to improve query efficiency, an oblivious location-based service query (OLBSQ) scheme is proposed. Our scheme captures the following features: (1) a semi-trusted TTP is not required; (2) a user can query services from a service provider without revealing her exact location; (3) the service provider can only know the size of a query made by a user; and (4) both the computation cost and the communication cost to generate a query is constant, instead of linear in the size of the queried area. We formalise the definition and security model of OLBSQ schemes. The security of our scheme is reduced to well-known complexity assumptions. The novelty is to reduce the computation cost and communication cost of making a query and enable the service provider to obliviously and incrementally generate decrypt keys for queried services. This contributes to the growing work of formalising privacy-preserving LBS schemes and improving query efficiency.