In this paper, we introduce a cross-layer framework for enhancing privacy in RFID systems. The framework relies on mechanisms in the physical (PHY) layer, as well as the medium access control (MAC) layer, to provide flexible protection over the unique identifiers of low-cost RFID tags. Such a framework prevents adversaries and malicious parties from tracking RFID tags through the monitoring of their unique identifiers. More specifically, our framework relies on masking of the identifier at the PHY layer, whereby bit-collisions are induced between the backscattered tag identifier and a protective mask, such that a legitimate reader can be allowed to recover the tag identifier but an illegitimate party would not be able to do so. To strengthen the level of protection provided by the bit-collision masking method, we present the randomized bit encoding scheme that is used in our framework. In addition, we also incorporate mechanisms in the MAC layer, and make use of cross-layer interactions between the MAC and the PHY layers to provide flexible privacy protection. This allows tags that do not require privacy protection to be read conveniently while allowing tags that need to be protected to stay protected.
This research is not carried out under any specific funding.