A Digital Content Protection Scheme Using MPEG-21 REL with Applications to DVB systems Ying-Tzu Shih, Feng-Cheng Chang, and Hsueh-Ming Hang Department of Electronics Engineering, National Chiao Tung University, TAIWAN enz.ee92g@nctu.edu.tw, breeze@alumni.nctu.edu.tw, hmhang@mail.nctu.edu.tw Abstract In a digital TV system, the Conditional Access (CA) system is essential to protect programs from unauthorized access. However, the encryption technique alone is not sufficient to protect or control the use of contents after decryption. To provide flexible and complete Digital Rights Management (DRM) protection on the Digital Video Broadcasting (DVB) programs, we propose a method that adapts the MPEG- 21 REL technology and integrates it into a DVB-T system. By extending the Service Information (SI) section of a DVB stream to include an REL license, the transmitted content can be conveniently consumed and legally protected. Our design is verified by an experimental hardware system. The results show that the proposed method can provide both the conditional access functionality and the usage control of broadcasted contents. 1. Introduction In the Digital Video Broadcasting (DVB) system, the Conditional Access (CA) module is included to protect contents from unauthorized access. Typically, the encryption technique is adopted as the main tool in a CA system. However, it is outside the scope of a CA system to control the use of digital contents after they are received and decrypted. We need to use the other sophisticated tools that are able to control the playback, re-distribution, and other operations of the received digital media. Digital Rights Management (DRM) is aiming at managing and protecting digital contents in their life cycle. It provides not only the access control; it also manages the use rights afterwards. It can cover various kinds of content consumption scenarios. A typical DRM system should provide a safe, open, and trusty platform for content production, delivery, and consumption. A recently approved ISO standard, MPEG-21 Part 5 --- Rights Expression Language (REL) [1], is an important technology to support guaranteed end-to-end interoperability, consistency and reliability between different systems and services. It is an XML- based language, which is used to declare rights and conditions for the authorized distribution and use of any content, resources, or services. In this paper, we propose a method to incorporate an MPEG-21 REL license into a DVB stream to provide a flexible and complete DRM mechanism for broadcast programs. The rest of the paper is organized as follows. In sec. 2, we give an overview of a typical DVB system. In sec. 3, we discuss the structure and usage of the MPEG-21 REL. Then, we describe the details of our proposed system structure/algorithm in sec. 4. We also provide two examples to demonstrate the design. We conclude this presentation with sec. 5. 2. Digital video broadcasting system In 1995, the Digital Video Broadcasting (DVB) project organized by the European Broadcasting Union (EBU) published a set of standards that specify a series of digital broadcast TV systems. These standards are widely used in Europe, Asia, Australia, and in many other regions of the world since 1996. A digital TV program is typically transmitted as an MPEG-2 transport stream. A transport stream may contain one or more services. Each service consists of a group of elementary streams that make up a TV channel. Each TV program is known as an event, which may contain at least one audio stream, one video stream, and optionally other data streams. A service is a series of individual events broadcasted one after another. A transport stream contains also a number of system headers. In addition to the Program Specific Information (PSI) defined by the MPEG to describe the structure of a transport stream [2], the DVB standard specifics the Service Information (SI) that describes the services in a transport stream [3]. The SI data are structured as tables with nine types of information. Each SI table contains descriptors for a specific service or event. There are many pre-defined descriptor types in the DVB specifications. By combining different Proceedings of the 2006 International Conference on Intelligent Information Hiding and Multimedia Signal Processing (IIH-MSP'06) 0-7695-2745-0/06 $20.00 © 2006