Privacy-preserving revocable content sharing in geosocial networks

Location-based services enable people to obtain various kinds of services based on their current locations. Recently, the geosocial networking services, which utilize mobile users´ location information to realize social interactions, lead to numerous fascinating applications, such as content sharing, social shopping, food sourcing, and so on. However, extensive and unnecessary uses of mobile users´ spatial and temporal information pose conspicuous privacy threats not only to their locations, but also to the shared contents, which may contain sensitive information, such as special interests, real identity, and crucial social relationships. To preserve the privacy of mobile users, we may apply the attribute-based encryption (ABE) schemes to secure mobile users´ location and their contents. Unfortunately, existing approaches fail to jointly consider the privacy of the past shared contents and the accessibility of the updated contents for non-revoked users. In this paper, we propose a privacy-preserving revocable content sharing scheme in geosocial networks. Our scheme allows mobile users to share their encrypted location-based contents on an untrusted server without revealing actual location information, and further enables other mobile users who physically check in at the particular location to search and decrypt the content if they have the corresponding attributes. Importantly, to secure mobile users´ past shared contents and the corresponding location information, we design an efficient ciphertext update scheme to allow encrypted shared contents to be periodically updated and become inaccessible to revoked users. By trace-driven simulations, we show both the efficiency and privacy preservation of the proposed scheme.