Zhang Fengbin, born in 1965. He received his Ph.D degrees in College of Computer Science and Technology of Harbin Engineering University in 2005, He also received his B.S. and M.S. degrees from Harbin University of Science and Technology in 1988 and 1997 respectively. His research interests include the network security and information security. To whom correspondence should be addressed. E-mail:xinran@shmtu.cdu.cn Received on Apr.23, 2010