“…There exist two main approaches of designing chaos-based cryptosystems: analog mode and digital mode. From 1989, along with the use of analog chaotic systems in the design of secure communication systems [Alvarez, 1999;Zhou and Ling, 1997;Lai et al, 1999;Memon, 2003;Parlitz et al, 1992;Chen et al, 2003], applications of computerized (also called digital) chaotic systems in cryptography have attracted more and more attention [Baptista, 1998;Hong and Xieting, 1997;Jakimoski and Kocarev, 2001;Masuda and Aihara, 2002;Matthews, 1989;Papadimitriou, 2001;Guan et al, 2005;Xiao et al, 2005;Tang et al, 2005;Huang and Guan, 2005]. This paper chiefly focuses on the digital chaotic ciphers.…”