Abstract: Group Key Agreement（GKA） is an important research point in key establishment field. This paper proposes a new ID-based GKA protocol in ternary tree structure. It also considers the situation when some participants change. It discusses the security and computational cost of the new scheme. The result shows that the new protocol realizes the secure key agreement with lower computational cost.

Key words: cryptography, secure protocol, group key agreement, bilinear pairing, ternary tree

摘要： 群密钥协商是密钥协商协议的一个重要研究分支。提出了一种在三叉树结构下基于身份的群认证密钥协商协议，充分考虑了成员加入和离开时的子协议。还对方案的安全性和性能进行了分析。结果表明，新方案在计算量减少的前提下实现了协议多方的安全密钥协商。

关键词: 密码学, 安全协议, 群密钥协商, 双线性对, 三叉树