Anonymous authentication protocols with credit-based chargeability and fair privacy for mobile communications

Smart and tiny mobile phones are widely popularized and advanced mobile communication services are provided increasingly such that ubiquitous computing environments will come true soon. It is a pleasure for mobile users to work or get recreations in the mobile network environments. However, just as the cases in wireline networks, there are many security threats to mobile network systems and their impact on the security is more serious than that in wireline networks owing to the features of wireless transmissions and the ubiquity property in mobile network systems. The secret personal information, important data, or classified documents which mobile users carry may be stolen by malicious entities. In order to guarantee the quality of the advanced communication services, the security and privacy would be important issues when mobile users roam to the mobile networks. In this paper, an anonymous authentication scheme will be proposed to protect both the security of the mobile network system and the privacy of mobile users. Not only does the proposed scheme provide mutual authentication between each user and the system, but also the identity of each user can be kept secret against anyone else, including the system. Although the system anonymously authenticates the users, it can still make correct bills to charge these anonymous users. Finally, our protocols also achieve the goal of fair privacy which allows the judge to be able to revoke the anonymity and trace the illegal users when they misused the anonymity property such as they committed crimes.