Background and Objectives: Radio Frequency Identification (RFID) systems use radio frequency waves to exchange information between a legitimate sender and a receiver. One of the important features of RFID systems is to find and track a specific tag among a large number of tags. Numerous works have been done about authentication and ownership protocols, but the number of researches done in the tag searching area is much less. Although security is a paramount factor in search protocols, but these days designers are looking for a secure search protocol that is also low cost. One way to have a low cost search protocol is that to be compatible with EPC C1G2 standard, which is an electronic product code class 1 generation 2 that works in the 860-960 MHz frequency range.
Methods: Most recently, Sundaresan et al. have proposed an RFID tag search protocol based on quadratic residues and 128 bit pseudo random number generators and XOR operation that can be easily implemented on passive tags and is compatible with EPC C1G2 standard. We show that this protocol is not immune against tag tracing, and try to improve the protocol in a way that traceability attack will not be applicable and the protocol stays low cost and EPC compatible.
Results: Since the problem in Sundaresan et al.'s search protocol is due to the tag not being able to recognize the used queries from the new ones, we improved the protocol using a counter within the queries, so the tag will realize that the query is used or not. Then we analyze the security of the improved protocol and prove its formal and informal security against known attacks.
Conclusion: In this paper, we firstly analyze the security of Sundaresan et al.'s search protocol and show that the search protocol is vulnerable to traceability attack with two different scenarios. Then we propose an improved search protocol that is secure against tracing the tags. Following that, we analyze the security of the improved search protocol.
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