Abstract
Digital Rights Management (DRM) system protects and manages digital contents such that only authorized users can access media correctly and the others can not. DRM system can be further divided into device-based and identity-based DRM system. For device-based DRM system, a digital content is only allowed to be played on a particular device according to the license purchased. Therefore, if a user who owns two or more devices wants to play the same content on the device, he must purchase two or more licenses. This breaks off the habit of consumers in the real world. On the contrary, identity-based DRM system can meet more con-sumers’ expectations. A user is allowed to play a digital content anywhere and anytime once he purchases a license for the media. An identity-based DRM sys-tem was proposed by Conrado et al. recently, however, there are some drawbacks in their system. In this research, we improve their system in order to correct these drawbacks. Our proposed DRM system not only retains some useful properties as those in their system, e.g., privacy and mobility, but also provides more strong properties, including stealing proof, secrecy, and practicability. The other issue discussed in this research is privacy. Several DRM systems has been proposed and implemented for users to purchase digital contents online without illegal spreading of the contents. However, those implementations would expose the users’ privacy – revealing what contents they have purchased. Some proposals address the problem by providing anonymity to the user. Anonymous trade would not allow the shopkeepers to manage users efficiently. Also, the identities of users can still be profiled via side channels like routing paths or IP addresses. In this research, we propose a scheme to preserve users’ privacy by no means of anonymity. Instead, we hide the users’ choices of contents from the shopkeepers using oblivious transfer (OT). We will evaluate our scheme in the aspects of security, performance, comparison, and implementation. A privacy measurement called “Privacity” is also firstly defined.