Extending an RFID Security and Privacy Model by Considering Forward Untraceability

There are numerous works on the privacy and the security problems for RFID systems. However, many of them have failed due to the lack of formal security proof. In the literature, there are a few formal models that consider forward untraceability. In ASIACRYPT 2007, Vaudenay presented an new security and privacy model for RFID that combines early models to more understandable one. In this paper, we revisit Vaudenay's model and modify it by considering the notion of forward untraceability. Our modification considers all message flows between RFID reader and tags before and after compromising secrets of tag. We analyze some RFID schemes claiming to provide forward untraceability and resistance to server impersonation. For each scheme, we exhibit attacks in which a strong adversary can trace the future interactions of the tag and impersonate the valid server to the tag. Further, we show that a previously proposed attack claiming to violate forward untraceability of an existing MID scheme does not violate forward untraceability.