On logical domains for flexible content protection systems

Modern digital rights management (DRM) systems recognize that users want to play content on multiple devices - the (authorized) domain. However, the concept of domain is often too rigid: typically, the domain size is limited, and it is hard to remove a device and add another. It is even harder to transfer content between domains, and to lend it to friends. This paper analyses the current situation and proposes to introduce logical domains, which support logical operations such as union and intersection. Together with user input on how to adapt his domain, this allows for enough flexibility to keep users happy, and the content secure.