Vulnerability of an RFID Authentication Protocol Proposed in at SecUbiq 2005

In this paper, we analyze the security of the RFID authentication protocol proposed by Choi et al. at SecUbiq 2005. They claimed that their protocol is secure against all possible threats considered in RFID systems. However, we show that the protocol is vulnerable to an impersonation attack. Moreover, an attacker is able to trace a tag by querying it twice, given the initial information from 2dlog2(`+1)e + 1(≈ ` + 2) consecutive sessions and 2 · 2dlog2(`+1)e(≈ 2(` + 1)) consecutive queries, where ` is the length of secret values (in binary).