Abstract. Key exposures bring out very serious problems in security services. Especially, it is more severe in the applications such as electronic cash or electronic payment where money is directly involved. Forward secrecy is one of the security notions addressing the key exposure issues. Roughly speaking, forward secrecy is aimed to protect the validity of all actions using the secret key before the key exposure. In this paper, we investigate the key exposure problem in blind signature (with an application to the electronic cash in mind) and propose a blind signature scheme which guarantees forward secrecy. Our scheme is constructed from the provably secure Okamoto-Guillou-Quisquater (OGQ for short) blind signature scheme. Using the forking lemma by Pointcheval and Stern [4], we can show the equivalence between the existence of a forger with the solvability of the strong RSA problem. Further we show that our scheme introduces no significant communication overhead comparing with the original OGQ scheme.
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 this paper we attempt to summarize current research works in the field of RFID security and discuss some of their open issues. Firstly, we outline the security threats to RFID, then we summarize some of the current countermeasures and finally, we draw attention to the open issues and challenges in RIFD security. • Hash-based Protocols: Weis et. al. [3] introduced two hash-lock based authentication schemes. But they suffer from secret key disclosure problem, impersonation attack and violation of tag anonymity [14]. Ohkubo et.
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