Journal of Digital Information Management Cheng-Chi Lee, Ting-Yao Cheng, Te-Yu Chen 8 5 2010 http://www.dline.info/fpaper/jdim/v8i5/2.pdf In practice, we usually require a key agreement protocol to establish a common secret key for enciphering/deciphering messages. Now, most protocols can establish n2 common secret keys in a single round of messages exchange. In this paper, we shall propose an extended protocol to establish 2n2 common secret keys in a single round. The proposed protocol is based on bilinear pairings. Moreover, the correctness, security, and efficiency of our proposed protocol are presented.