Research On Multi-party Security Protocols

This thesis cents on the study of efficient and secue multi-party protocols, such as group key exchange, threshold proxy signcryption and (M+l)^st price auction scheme. By analyzing some related protocols that have been proposed recently, the author pointed out the deficiencies that exists in these protocols and then presented some new solutions. Comparison in terms of communication cost and security shown that integrade performance of new solutions outperforms that of originally proposed protocols, we present our researches in three ways as follows:(1) Efficient two rounds contributory GKE protocols from pairingsSince Joux proposed to design one round tripartite key exchange from pairings, more and more group key exchange (GKE) protocols from pairings have been presented. However in most schemes of GKE from pairings proposed so far were not constant round, and such schemes are neither scalable nor practical since the number of group members may be quite large and the efficiency of the schemes is severely degraded with only one member's delay. In this paper an efficient two rounds key exchange protocol from pairings has been presented. Compared with originally protocol that has been proposed by Du et. al, this scheme saved communication cost and computation cost. Then two extention types of this protocol were proposed. One of them is a robust contributory key exchange protocol resilient to intermittent links in some degree. It can resist some members' unexpected departure at the second round while these memebers have exchanged their contributory informantion for group key at the first round. So this protocol can be used in unstable environment such as ad hoc network and so on. The other one can not only generates secret session key for one group but also generates keys for subgroups that exist in this group. Furthermore the communication cost of this new...