Privacy-preserving identity-based file sharing in smart city

People are experiencing an evolution of smart cities. Building a smart city will enhance economic competitiveness, social cohesion, and quality of life of its citizens. But smart cities accumulate and process large amount of files, which raises security and privacy concerns at individual and community levels. In the case of file sharing in smart cities, security should be considered to embrace file confidentiality, file integrity, receiver privacy, and sender privacy. In this paper, we propose a privacy-preserving identity-based file sharing (PIFS) scheme to meet these security goals. In PIFS, identity managers for receivers and senders designate them secret keys associated with their identities, respectively. Receivers and senders can register their identities to the group managers without leaking their secret keys. Then a sender can share confidential files with a peer, leaking neither identity of them. However, in case of dispute, the receiver group manager and sender open authority can trace the receiver and the sender, respectively. The security properties of our scheme are formally proven. Analysis shows that our scheme is efficient and practical.