Extended Asymmetric Group Key Agreement for Dynamic Groups and Its Applications

Group Key Agreement(GKA)is a cryptographic primitive allowing two or more entities to negotiate a shared session key over public networks.In existing GKA models,it is an open problem to construct a one-round multi-party GKA protocol.Wu et al.recently proposed the concept of asymmetric group key agreement(ASGKA)and realized a one-round ASGKA protocol,which affirmatively answers the above open problem in a relaxed way.However,the ASGKA protocol only applies to static groups.To fill this gap,this paper proposes an extended ASGKA protocol based on the Wu et al.protocol.The extension allows any member to join and leave at any point,provided that the resulting group size is not greater than n.To validate the proposal,extensive experiments are performed and the experimental results show that our protocol is more effective than a plain realization of the Wu et al.protocol for dynamic groups.The extended protocol is also more efficient than the up-to-date dynamic GKA protocol in terms of communication and computation.

Identity Based Group Key Agreement in Multiple PKG Environment

Secure and reliable group communication is an increasingly active research area by growing popularity in group-oriented and collaborative applications. In this paper, we propose the first identity-based authenticated group key agreement in multiple private key generators （PKG） environment. It is inspired on a new two-party identity-based key agreement protocol first proposed by Hoonjung Lee et al. In our scheme, although each member comes from different domain and belongs to different PKGs which do not share the common system parameters, they can agree on a shared secret group key. We show that our scheme satisfies every security requirements of the group key agreement protocols.

Password-Based Group Key Agreement Protocol for Client-Server Application

The security issue is always the most important concern of networked client-server application. On the putpose to build the secure group communication among of a group of client users and one server, in this paper, we will present a new password-based group key agreement protocol. Our protocol will meet simplicity, efficiency, and many desired security properties.

Identity Based Group Key Agreement from Bilinear Pairing

We present a provably secure authenticated tree based key agreement scheme for multicast. There is a wide variety of applications that can benefit from using our scheme, e. g. , pay-Tv, teleconferencing, software updates. Compared with the previous published schemes, our scheme provides group member authentication without introducing additional mechanism. Future, we give the security proof of our scheme under the random oracle model.

ID-Based Authenticated Dynamic Group Key Agreement

Two ID-based authenticated group key agreement schemes, proposed by Choi et al and Du et al, are insecure against an impersonation attack and th ey only discussed the static group. This paper proposed a variant of BD protocol , which is fully authenticated by a proven-secure ID-based signature scheme. T he protocol can res ist the impersonation attack, and other security attributes are also satisfied. Compared with Choi et al and Du et al schemes, the proposed one is mor e efficient and applicable for dynamic groups.

An Improved ID-Based Group Key Agreement Protocol

ID-based constant-round group key agreement protocols are efficient in both computation and communication, but previous protocols did not provide valid message authentication. An improvement based on attack analysis is proposed in this paper. The improved method takes full advantage of the data transmitted at various stages of the protocol. By guaranteeing the freshness of authentication messages, the authenticity of the generator of authentication messages, and the completeness of the authenticator, the improved protocol can resist various passive and active attacks. The forward secrecy of the improved protocol is proved under a Katz-Yung （KY） model. Compared with existing methods, the improved protocol is more effective and applicable.

A dynamic,secure,and efficient group key agreement protocol

The key challenge of dynamic peer communication is how to realize secure and efficient group key manage-ment.A two rounds key agreement protocol for dynamic peer group(DPG)is proposed in this paper.The protocol,which was obtained by combining the ElGamal encryption scheme with the ElGamal signature scheme,is efficient and simple.The protocol is proven secure against passive attack by using indistinguishable method.Moreover,both perfect forward secrecy(PFS)and key independence(KI)were achieved.Because the protocol is based on the broadcast channel,it is also suitable for key agreement in wireless communications,especially in ad-hoc networks.

Authenticated Group Key Agreement Protocol Based on Twist Conjugacy Problem in Near-Rings

Nowadays some promising authenticated group key agreement protocols are constructed on braid groups, dynamic groups, pairings and bilinear pairings. Hence the non-abelian structure has attracted cryptographers to construct public-key cryptographic protocols. In this article, we propose a new authenticated group key agreement protocol which works in non-abelian near-rings. We have proved that our protocol meets the security attributes under the assumption that the twist conjugacy search problem（TCSP） is hard in near-ring.

A Layer-Cluster Key Agreement Protocol for Ad Hoc Networks

Mobile ad hoc networks create additional challenges for implementing the group key establishment due to resource constraints on nodes and dynamic changes on topology. The nodes in mobile ad hoc networks are usually low power devices that run on battery power. As a result, the costs of the node resources should be minimized when constructing a group key agreement protocol so that the battery life could be prolonged. To achieve this goal, in this paper we propose a security efficient group key agreement protocol based on Burmester-Desmedt （BD） scheme and layer-cluster group model, referred to as LCKM-BD, which is appropriate for large mobile ad hoe networks. In the layer-cluster group model, BD scheme is employed to establish group key, which can not only meet security demands of mobile ad hoc networks but also improve executing performance. Finally, the proposed protocol LCKM-BD are compared with BD, TGDH （tree-based group Diffe-Hellman）, and GDH （group Diffie-Hellman） group key agreement protocols. The analysis results show that our protocol can significantly decrease both the computational overhead and communication costs with respect to these comparable protocols.

nPAKE^+:A Tree-Based Group Password-Authenticated Key Exchange Protocol Using Different Passwords

Although two-party password-authenticated key exchange （PAKE） protocols have been intensively studied in recent years, group PAKE protocols have received little attention. In this paper, we propose a tree-based group PAKE protocol - nPAKE^＋ protocol under the setting where each party shares an independent password with a trusted server. The nPAKE^＋ protocol is a novel combination of the hierarchical key tree structure and the password-based Diffie-Hellman exchange, and hence it achieves substantial gain in computation efficiency. In particular, the computation cost for each client in our protocol is only O（log n）. Additionally, the hierarchical feature of nPAKE^＋ enables every subgroup to obtain its own subgroup key in the end. We also prove the security of our protocol under the random oracle model and the ideal cipher model.