Authenticated Key Agreement Protocol

Nowadays, the computer network technology and the information technology have been getting more and more important. How to assure the information security is one of the most important fields. At present, much information security depends on the cryptography. As a branch of it, key agreement protocol is a very important subject in the information security. People want to communicate securely with each other through non-security channel, the establishment of seesion key is very critical. Therefore, research on key agreememt protocol is important both in theory signification and application. Authenticatied key agreement protocol is one kind of key agreement protocols which adds the authentication mechanism into the agreement. Authenticatied key agreement protocol is widely used in recent years, and it has got much new development.Many researchers are focus on the study of authenticated key agreement protocol between 3 parties. In this paper, we firstly point out that there is a weakness in S-3PAKE protocol proposed by Lu et al. in 2006, and give the process of how to attack this protocol with the on-line guessing attack. Then, we propose a new simple 3 parties authenticated key agreement protocol based on the CDH problem, and proved our new protocol can resist all kinds of attacks efficiently.The authenticated group key agreement protocol is also a challenging task. In this paper, we firstly introduce Tseng's and Cho et al's protocols, point out Cho et al's protocol can not resist the replay attack efficiently. Then we suggest a countermeasure to enhance the security of their protocol. Lastly, we propose a new authenticated group key agreement protocol based on the bilinear pairing and prove our new protocol can resist all kinds of attacks efficiently.