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We construct a short group signature which is proven secure without random oracles. By making certain reasonable assumptions and applying the technique of non-interactive proof system, we prove that our scheme is full anonymity and full traceability. Compared with other related works, such as BW06 [9], BW07 [10], ours is more practical due to the short size of both public key and group signature. [ABSTRACT FROM AUTHOR]

To construct a suitable and secure proxy re-signature scheme is not an easy job, up to now, there exist only three schemes, one is proposed by Blaze et al. [6] at EUROCRYPT 1998, and the others are proposed by Ateniese and Hohenberger [2] at ACM CCS 2005. However, none of these schemes is proved in the standard model (i.e., do not rely on the random oracle heuristic). In this paper, based on Waters' approach [20], we first propose a multi-use bidirectional proxy re-signature scheme, denoted as Smb, which is existentially unforgeable in the standard model. And then, we extend Smb to be a multi-use bidirectional ID-based proxy re-signature scheme, denoted by Sid − mb, which is also existentially unforgeable in the standard model. Both of these two proposed schemes are computationally efficient, and their security bases on the Computational Diffie-Hellman (CDH) assumption. [ABSTRACT FROM AUTHOR]

Transitive signature is an interesting primitive due to Micali and Rivest. During the past years, many constructions of transitive signatures have been proposed based on various assumptions. In this paper, we provide the first construction of transitive signature schemes by using braid groups. In the random oracle model, our proposals are proved to be transitively unforgeable against adaptively chosen message attack under the assumption of the intractability of one-more matching conjugate problem (OM-MCP) over braid groups. Moreover, the proposed schemes are invulnerable to currently known quantum attacks. [ABSTRACT FROM AUTHOR]

Exposure of secret keys can be the most devastating attack on a signature scheme since such that security is entirely lost. In a certificated based environment, the certification revocation list (CRL) can be used to minimize the damage caused by key exposure. In an identity based environment however, key exposure may means that the corresponding entity of the exposed key cannot use his identity information as his public key any more, and is in fact removed from the identity based system. In last few years the notion of and implementations of key insulated cryptosystems have been suggested for protecting the security of cryptosystems. In this work, we apply the method of key insulation to identity based signature, and solve the key exposure problem existing in the identity based schemes. We start by developing the formal model for identity based key insulated signature. We then use the fact to construct a identity based key insulated signature scheme. Keywords: identity based cryptosystem, key insulated cryptosystem, bilinear Diffie-Hellman. [ABSTRACT FROM AUTHOR]

Password authentication has been accepted as an easy-to-use solution in network environment to protect unauthorized access to a remote server. Although many schemes have been proposed, none of them can achieve survivability in case of compromise of a server. Once a server’s secret key is leaked, the system is totally broken, and all the legally registered users have to be rejected for security reason, which is the most undesirable tragedy in business applications. In this paper, we propose a remote authentication scheme with forward security to reduce the potential damages caused by key exposure problem in authentication schemes. In our scheme, an intruder can not masquerade as an legal user registered at previous periods even if he has obtained server’s secret keys. [ABSTRACT FROM AUTHOR]

With the flourish of applications over the wired /wireless networks, how to keep user's privacy has drawn growing concerns in recent years. Although the issue of user anonymity has been addressed in digital signature field by introducing the concepts of ring and group signatures, they are not suitable to anonymously authenticate a user in wireless mobile applications, because these signature schemes need infrastructure support and heavy computational costs which is beyond the computational ability of a smart card embedded in a hand-held device. In this paper, we propose an anonymous authentication scheme which also supports Diffie-Hellman key exchange. Our scheme is very efficient since it mainly uses hash and XOR operations. Moreover, our scheme possesses many good virtues of existing authentication schemes. [ABSTRACT FROM AUTHOR]