Study On Digital Rights Management System And Its Protocols

In recent years, with the rapid development of the Internet and multimedia technique, digital contents can be freely produced and then be propagated through the networks. However, the arbitrary copy and redistribution to the digital contents make the copyrights infringement in the networks very serious. The legal rights of the rights holders and relative people are greatly harmed and it obstructs the digitalized industry in developing healthily and orderly. So, how to protect the copyrights of the digital contents is becoming an important problem to the industry.As an effective technique to solve the problem, DRM (Digital Rights Management) catches the researchers' more and more attentions. The technique is used to ensure the legal use during the whole life circle of the digital contents, and it can balance the benefits and requirements of each role in the digital content value chain.At present, most DRM systems save the digital license which is necessary while using the digital content in the user end. It would bring some security problem. Besides, the existing DRM systems emphasize the distribution of rights between the rights holders and common users, but pay very little attention to rights redistribution between the common users. A DRM system based on mobile agent for digital rights redistribution is proposed and the main protocols of it are analyzed. In the system, the mobile agent is deployed on behalf of content provider. It carries the digital license and arrives in the user end to enforce the DRM functions honestly, and returns to the sender end after execution, this prevents the digital license from saving in the user end. The security of the mobile agent itself can be assured by creating a time limit blackbox out of an original mobile agent. Rights redistribution supported by the system can increase the motivation for users to buy and use contents and decrease the possibility to crack the DRM system. Besides, the digital watermarking is embedded in the digital content issued by the content provider to copyrights pursuit.With the popularization of the electronic products and the development of the communication technology, home network is becoming a hotspot to the researchers. The unique properties of the home network make the common DRM systems in the market not suitable for it, for example, in the home network, users usually wish the contents can be conveniently shared, but most DRM systems don't support it. According to the analysis of the existing DRM proposals for home network, we can find that they have some shortages about rights management mode,flexibility of management and security. So a home network oriented DRM system is proposed and the main protocols of it are analyzed. In the system, home gateway manages all the user terminals in the home network by creating a domain, and requires digital content and license from the DRM system in the Internet as their agent. The right required by the home gateway bases on all the user terminals in the home network domain, and it allows the content sharing between the user terminals which have legally registered in the domain through the super distribution mode, and the group key technique can ensure that the encrypted content is only decrypted and used by the legal user terminals. Besides, the system embeds the digital fingerprint of the home gateway. As a result, when the pirated copy of the issued content is found, the digital fingerprint is used in locating the precise home network and investigating it according to law.There are many DRM systems in the market now, but the format of the provided contents and licenses and the operation methods of the DRM systems all exist distinct. It brings huge inconvenience to users and disturbs the further development of the market. The main measure to solve the problem is the interoperability technique. Through the analysis to some current schemes to solving DRM interoperability, we can find them lack in user end burden and security etc. So a supporting system for DRM interoperability is proposed and the main protocols of it are analyzed. The system can connect different DRM systems and apply content access between DRM systems through format conversion. The system is applied by the specific convincing server and adopts Public key infrastructure technique to ensure security. The analysis shows the system has some advantage in security and work efficiency.