Extending ECC-based RFID authentication protocols to privacy-preserving multi-party grouping proofs

Since the introduction of the concept of grouping proofs by Juels, which permit RFID tags to generate evidence that they have been scanned simultaneously, various new schemes have been proposed. Their common property is the use of symmetric-key primitives. However, it has been shown that such schemes often entail scalability, security and/or privacy problems. In this article, we extend the notion of public-key RFID authentication protocols and propose a privacy-preserving multi-party grouping-proof protocol which relies exclusively on the use of elliptic curve cryptography (ECC). It allows to generate a proof which is verifiable by a trusted verifier in an offline setting, even when readers or tags are potentially untrusted, and it is privacy-preserving in the setting of a narrow-strong attacker. We also demonstrate that our RFID grouping-proof protocol can easily be extended to use cases with more than two tags, without any additional cost for an RFID tag. To illustrate the implementation feasibility of our proposed solutions, we present a novel ECC hardware architecture designed for RFID.