Coexistence Proof Using Chain of Timestamps for Multiple RFID Tags

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How can a RFID (Radio Frequency Identification Devices) system prove that two or more RFID tags are in the same location? Previous researchers have proposed yoking-proof and grouping-proof techniques to address this problem – and when these turned out to be vulnerable to replay attacks, a new existence-proof technique was proposed. We critique this class of existence-proofs and show it has three problems: (a) a race condition when multiple readers are present; (b) a race condition when multiple tags are present; and (c) a problem determining the number of tags. We present two new proof techniques, a secure timestamp proof (secTS-proof) and a timestamp-chaining proof (chaining-proof) that avoid replay attacks and solve problems in previously proposed techniques.

This research was supported in part with funding from the iCAST project NSC95-3114-P-001-002-Y02 in Taiwan, from the US National Science Foundation, from the US Air Force Office of Scientific Research, and from the Taiwanese National Science Council. The opinions expressed in this opinion are solely those of the authors and do not necessarily reflect the opinions of any funding sponsor.