Linkable Privacy-Preserving Scheme for Location-Based Services

Query content privacy and location privacy of the user and point of interest (POI) of the service provider are a serious concern for location-based services (LBS). The current LBS schemes either protect the query content privacy or location privacy. To protect query content of the user and POI of the server, several schemes have been proposed based on k-anonymity, Oblivious transfer (OT), private information retrieval (PIR), and homomorphic encryption. To protect location privacy, the existing schemes either use cryptographic schemes or need a trusted third party (TTP) between the server and the user. A change of location requires re-execution of the core scheme, which causes communication and computational overhead. To address these problems, we propose a linkable location-based services (L2BS) scheme that uses Modified Linkable Spontaneous Anonymous Group (MLSAG) signature scheme and the OT scheme. The proposed MLSAG scheme provides privacy-preserving authentication with privacy preserving service linking. The OT protocol protects the query content of the user and the POI of the server. When a user requests for service and sends a query to the same server second time onwards, the L2BS scheme does not require re-execution of the OT. This, L2BSWOT scheme, decreases the communication and computation costs in addition to privacy-preserving linking of past and current queries from the same user. Results show that L2BS scheme with or without the need for OT execution (L2BSWOT scheme) outperforms other existing LBS schemes in terms of communication and computation costs while satisfying all privacy requirements of an LBS.