The emerging ubiquitous environment is improving IT technologies and the popularization of broadband Internet is encouraging creation and sharing of various contents. The contents include the concept of production and circulation of digital information/contents, in forms of characters, codes, voices, sounds, client and videos for being used on the Internet and networks. The contents are widely shared in networks and users can have a wide range of knowledge and gain the freedom of presentation from them. So now users participations are augmented gradually. However, many contents without acquiring agree of copyright are sharing on the Internet, so many problems happen in the manufacturing process of digital contents. To solve this problem, many research projects to limit contents utilization onto legitimate users and to provide secure contents protection and download, are in progress. Therefore, in this paper, we propose a secure D-CAS system (SDCS) which provides security for contents downloading.