Abstract
Secure group communication over an untrusted open network is a serious problem, especially for mobile environment. With the development of network and its application, many group-oriented applications are increasing rapidly. Additionally, mobile devices are more powerful and growing popularity. To achieve secure group communication, we need a group key to protect data. We present an authenticated group key agreement protocol for mobile environments. The protocol combines a short certificateless signature scheme, which has the advantage of overcoming the management cost of certificate in traditional PKI and the key escrow problem in ID-based PKI. In our protocol, we use a semi-trusted server instead of a full-trusted server. The semi-trusted setting makes the group key more secure for group members. According to the result of analysis, our protocol can provide more secure and acceptable efficient.