Kang Zhiwei was born in 1962. He is an associate professor with School of Computer and Communication, Hunan University. His main research interests include signal processing, information security and pattern recognition. E-mail: hn-zwkang@126.com Liu Jing was born in 1981. He is a graduate student in School of Computer and Communication, Hunan University. His main research interests include digital image processing and information security. He Yigang was born in 1966. He is a professor with School of Electrical and Information Engineering, Hunan University. His main research interests include signal processing and fault diagnosis of analog circuits.