Privately Identifying Location Hotspots

The ability to identify location hotspots – locations that are currently popular – is frequently used by locationbased services to tune their recommendation and advertising systems. We present an efficient system that lets locationbased services identify location hotspots, but without learning who is at those locations. The service also learns popular activities at hotspots, but learns nothing about who is engaging in these activities. Thus, our system strikes a balance between the service’s need to mine location data and user privacy. The system is proven secure in a robust security model that protects against collusion between players and the server and protects against dishonest users who try to help a certain location appear more popular than it is.