Vulnerability of an RFID authentication protocol conforming to EPC Class 1 Generation 2 Standards

Recently, Chien et al. proposed an RFID authentication protocol, which consists of only the cyclic redundancy code (CRC) and the pseudo-random number generator (PRNG) [H. Chien, C. Chen, Mutual Authentication Protocol for RFID Conforming to EPC Class 1 Generation 2 Standards, Computer Standards & Interfaces, vol. 29, Elsevier, 2007, pp. 254–259]. They claimed that the protocol conforms to current EPC tags, and would be secure against all attacks on RFID systems. However, in this paper, we show that the protocol is not secure; firstly an attacker can impersonate a valid tag temporarily by a single eavesdropping. Secondly the attacker can forge a tag permanently by eavesdropping two consecutive sessions. Finally he can make a valid tag useless (DoS attack) by modifying the second attack slightly. The computational complexities of the attacks are so practicable that Chien et al.'s protocol cannot enhance the RFID security any more than the original EPC standard.