LPPRS: New Location Privacy Preserving Schemes Based on Ring Signature over Mobile Social Networks

Abstract

There are two popular location-based service (LBS) applications: searching k-nearest neighbor Points of Interests (kNN POIs) and finding Nearby Friends (NF) via a social network server (SNS). Nevertheless, both applications are based on users’ current locations, and no scheme has been devised yet to merge POIs, NF and SNS together. A series of works were proposed to preserve users’ query privacy leaked from service attributes of POIs or location privacy over Mobile Social Networks (MSNs). However, their communication and computation costs are heavy. In this paper, we design a novel LBS application named NFPOI, which allows users to search NF based on a given POI via an SNS. To preserve users’ identity privacy, location privacy and query privacy, we firstly propose Location Privacy Preserving schemes based on Ring Signature (LPPRS). In our LPPRS, (1) Both user’s real identity and real location are kept secret from others effectively. (2) Due to the anonymity of ring signature, the SNS was allowed to return query results while it cannot distinguish the real sender when processing a query message. Thus, the sender’s query privacy is preserved even though the SNS knows the actual attributes and locations of POIs. (3) Neither a fully trusted third party (TTP) nor a pre-shared secret key with friends is required. A semi-TTP scheme and a TTP-free scheme were proposed respectively with different trade-offs in efficiency and security level. (4) Communication and computation costs for user side are less than existing works.