中文摘要：

E-mail： shqli@mail.xidian.edu.cn Sheng-Qiang Li received the B.S. degree from University of Electronic Science and Technology of China in 2003. He is currently a Ph.D. candidate of Research Institute of Information Security, Xidian University, Xi＇an. His research interests include cryptography, information theory and LDPC code. Zhi-Xiong Chen received the M.S. degree in mathematics from Fujian Normal University in 1999 and the Ph.D. degree in cryptography from Xidian University in 2006. Now he is a lecturer of Putian University. His research interests are elliptic curve cryptography, hyperelliptic curve cryptography and algebra. Xiao-Tong Fu received the Ph.D. degree in cryptography from Xidian University in 2005. Now she is a lecturer of Xidian University. Her research interests are digital signature and information hiding. Guo-Zhen Xiao was graduated from the Department of Mathematics, Northeast Normal University, Changchun, China, in 1954. In 1956, he received the M.S. degree in mathematics from the East China Normal University, Shanghai, China. He is now a professor and Ph.D. advisor of cryptography in Communications Engineering School of Xidian University. His research interests include cryptography, coding and information theory.