2Ploc: Preserving Privacy in Location-based Services

Location-based services are becoming popular for mobile users. The mobile users´ location plays a key role to provide the service from one side, but it can be considered as a dimension of their privacy and so necessary to keep it anonymous to the other parties. Since one important issue is to achieve an accurate service, it is important to use the mobile´s accurate location. Using the location accurately raises some concerns on behalf of the user´s privacy. One solution for meeting this requirement is using tickets by the means of a third party. The tickets should have some properties for not letting a mobile user to cheat and use the ticket more than one time. This paper proposes a protocol to preserve Preserve Privacy in Location based services, in short 2PLoc, aimed to provide anonymity of location, for location based services, based on onetime tickets regardless of the existence of any trusted third party. The protocol satisfies the requirement of accurate location use, as well as the ability of revoking anonymity on the ticket double spending. The user, location-based service provider, and the ticket issuer are the three untrusted parties in 2PLoc. 2PLoc is based on a special designed ticket that disconnects the relation between the location of the mobile user and its identity. The ticket is designed based on the blind signature and the concept of elliptic curves discrete logarithm.