Privacy leakage in access mode: Revisiting private RFID Authentication protocols

Existing RFID Privacy-Preserving Authentication (PPA) solutions mainly focus on the design of crypto based interactive protocols between readers and tags. Although the cryptographic mechanisms enable randomization and enhance protocol-level privacy, the access mode in RFID systems is less random and may leak private information. We introduce a new attack based on such privacy leakage in access mode, where we show that the mainstream RFID PPA protocols, including the linear, tree-based, and synchronization-based solutions, are not private. We also show that this new attack is easy to conduct, e.g., we can track tags that employ typical tree-based PPA protocols without the need of compromising tags. We discuss the applicability of the attack. Moreover, we provide useful recommendations to strengthen existing PPA protocols in defending against such attacks. The simulation results demonstrate the practicability and effectiveness of this attack.