Blocker-Type Methods for Protecting Customers´ Privacy in RFID Systems

In this paper we present methods of protecting RFID tags users´ privacy. Based on well-known technique by Juels et al. called Blocker tag we introduce a set of methods for increasing security using a device called Hedgehog blocker. Hedgehog blocker copes with the problem of the additional information gained by the adversary through measuring signal power (i.e. learning the number of transmitting tags). We claim that although Hedgehog blocker would be more expensive than regular Blocker tags, it provides privacy protection within the context of a more realistic model. On the other hand Hedgehog blocker does not require any powerful devices like Selective jamming due to Rieback et al. We also introduce the ideas called Preventer and Proxy allower that are more demanding in terms of costs and computational power, however assuring nearly perfect protection against an adversary with ability to determine the number of antennas transmitting.