Digital Rights Management (DRM) system is a mechanism used to control the use of digital content according to the usage rules specified in the license. To avoid unauthorized accesses, DRM systems would bind the unique hardware ID to the license. In this way, however, it is inconvenient for consumers to play the purchased content on another device, and is uneasy about the information about what he/she purchases can be collected easily according the unique hardware ID. Recently, some novel DRM systems based on smart cards have been introduced to address these problems. However, some drawbacks on the security, practicability, and efficiency exist in these systems, which will be shown in this paper. In this paper, a smart card based DRM scheme addressing their drawbacks is proposed to provide portability, user privacy, security, practicability, and efficiency.