Recent emergence of RFID tags capable of performing public key operations motivates new RFID applications, including electronic travel documents, identification cards and payment instruments. In this context, public key certificates form the cornerstone of the overall system security. In this paper, we argue that one of the prominent challenges is how to handle revocation and expiration checking of RFID reader certificates. This is an important issue considering that these high-end RFID tags are geared for applications such as e-documents and contactless payment instruments Furthermore, the problem is unique to public key-based RFID systems, since a passive RFID tag has no clock and thus cannot use (time-based) off-line methods. In this paper, we address the problem of reader certificate expiration and revocation in PKI-Based RFID systems. We begin by observing an important distinguishing feature of personal RFID tags used in authentication, access control or payment applications -- the involvement of a human user. We take advantage of the user's awareness and presence to construct a simple, efficient, secure and (most importantly) feasible solution. We evaluate the usability and practical security of our solution via user studies and discuss its feasibility.
Nithyanand, R.; Tsudik, G.; Uzun, E. User-aided reader revocation in PKI-Based RFID systems. Journal of Computer Security. 2011; 19 (6): 1147-1172.