RFID security is a relatively new research area. Within less than a decade, a large number of research papers dealing with security issues of RFID technology have appeared. In the first part of this paper, we attempt to summarise current research in the field of RFID security and discuss some of their open issues. In the second part of this paper, we address some of the open problems we suggested in the first part. In particular, we deal with scalability problem of existing grouping-proof protocols for RFID tags. In addition, we also present the first security definition for a secure grouping-proof protocol for RFID tags. The definition is then used to analyse the security of our proposed grouping-proof protocol which employs a (n, n)-secret sharing scheme to solve the scalability problem of previous protocols. of Korea. He has served as the IACR Director and a Program Committee Member of many security-related conferences. His research interests include the theory and practices of cryptology and information security.