A Dynamic Approach to Hash-Based Privacy-Preserving RFID Protocols

Abstract

We study how to design a hash-based identification protocol in a RFID system which obtains security and privacy against active adversaries. Here, an active adversary can not only track a tag via successful or unsuccessful identifications with legal or illegal readers but also perform a compromised attack. In SPC 2003, Weis et al. used the technique of the randomized hash lock to design a privacy-preserving protocol against such active adversaries. However, in their protocol, the time complexity of identifying a requested tag is linear in the number of legal tags. It is still an open problem to design a protocol which obtains privacy against active adversaries and has a sublinear time complexity of tag identification.

In this work, we revisit this open problem. We modify the protocol of Weis et al. by using a dynamic key management scheme to manage tag identities stored in the back-end database instead of a static approach. For privacy, our protocol obtains the same privacy level as the protocol of Weis et al.. For performance, the amortized cost of tag identification of our protocol is almost twice the optimal amortized cost by a competitive analysis. For practical implementation, our protocol is very suitable to be realized in RFID systems due to its online property.