Privacy-preserving digital rights management

DRM systems provide a means for protecting digital content, but at the same time they violate the privacy of users in a number of ways. This paper addresses privacy issues in DRM systems. The main challenge is how to allow a user to interact with the system in an anonymous/pseudonymous way, while preserving all security requirements of usual DRM systems. To achieve this goal, the paper proposes a set of protocols and methods for managing user identities and interactions with the system during the process of acquiring and consuming digital content. Furthermore, a method that supports anonymous transfer of licenses is discussed. It allows a user to transfer a piece of content to another user without the content provider being able to link the two users. Finally, the paper demonstrates how to extend the rights of a given user to a group of users in a privacy preserving way. The extension hides the group structure from the content provider and at the same time provides privacy among the members of the group.