Sheng-Li Liu studied in School of Economic Management, Xidian University, Xi'an, from September 1991 till July 1995, where she got her Bachelor's degree, majoring in scientific information. From September 1995 till February 1998, she worked toward Master's degree in School of Computer Science, majoring in computer application. She received her Ph.D. degree from Xidian University in January 2002. From March 2000 till February 2002, she continued her research on cryptography at the discrete mathematics group, Department of Mathematics and Computer Science, Technische Universiteit Eindhoven. Supervised by Prof. dr. ir. Henk van Tilborg, she got another Ph.D. degree from Technische Universiteit Eindhoven on Feb 26, 2002 with a dissertation entitled by "Information-Theoretic Secret Key Agreement". Since 2002, she is an associate professor in Department of Computer Science and Engineering, and a research member of Cryptography and Information Security Lab led by Prof. Chen Kefei, Shanghai Jiao Tong University. Her research interests include ID-based cryptography and pairing-based cryptosystems. E-mail: liu-sl@sjtu.edu.cn Xiao-Feng Chen is an associate professor in the Department of Computer Science at Sun Yan-Sen University, Guangzhou, China. He obtained his Ph.D. degree in cryptography from School of Communication Engineering, Xidian University in 2003. He was a post-doc fellow in International Research Center for Information Security (IRIS), Information and Communications University (ICU), Korea from 2003 to 2004. His main research interests include public key cryptography and E-commerce security. E-mail: isschxf@mail.sysu.edu.cn Fang-Guo Zhang is a professor in the Department of Electronics and Communication Engineering at Sun Yan-Sen University in Guangzhou, China. He received the B.S. and M.S. degrees in 1996 and 1999. He obtained his Ph.D. degree in cryptography from School of Communication Engineering, Xidian University in 2001. He was a post-doc fellow in International Research Center fo