一个有效的动态组密钥协商协议

针对常数轮基于身份(ID-based)的可验证密钥协商协议存在协商通讯效率不高，以及没有涉及到当组成员变动时如何重新协商的问题，采用分布式两轮组密钥协商协议中的环形组成员结构，利用单轮三方密钥协商协议技术，使得第二轮密钥协商阶段所需的广播交互信息的成员数较现有协议减少一半，提高了通讯效率.将协议推广到组成员动态变化的情形，当成员关系变化时协商的代价只与变化成员的数目相关，而与组内成员总数无关.分析表明，该协议是安全的，并且协商效率优于现有协议.

An efficient dynamic group key agreement protocol

A new efficient dynamic group key agreement protocol was presented to reduce the communication cost in ID-based constant round authenticated group key agreement. All group members constructed a ring structure during the group key agreement. Utilizing the technology proposed in one round tripartite key agreement protocol, about half of group members did not need to broadcast their messages in the second round information exchange in this protocol. So the efficiency of this protocol was improved. Then the group key agreement protocol was extended to suit dynamic group membership. When the membership changed, the number of members participating in the message exchange was only dependent on the number of joining/leaving numbers instead of that of all members. Hence, the total communication cost in the protocol was reduced compared with other protocols. Analysis results show that it is a secure protocol and more efficient than other protocols.