CRFID: An RFID system with a cloud database as a back-end server

Radio-frequency identification (RFID) systems can benefit from cloud databases since information on thousands of tags is queried at the same time. If all RFID readers in a system query a cloud database, data consistency can easily be maintained by cloud computing. Privacy-preserving authentication (PPA) has been proposed to protect RFID security. The time complexity for searching a cloud database in an RFID system is O(N), which is obviously inefficient. Fortunately, PPA uses tree structures to manage tags, which can reduce the complexity from a linear search to a logarithmic search. Hence, tree-based PPA provides RFID scalability. However, in tree-based mechanisms, compromise of a tag may cause other tags in the system to be vulnerable to tracking attacks. Here we propose a secure and efficient privacy-preserving RFID authentication protocol that uses a cloud database as an RFID server. The proposed protocol not only withstands desynchronizing and tracking attacks, but also provides scalability with O(logN) search complexity.