One challenge of today's media industry is the protection of copyrights. Therefore Digital Rights Management (DRM) is well established, see e.g. “Digital Rights Management” in http://www.microsoft.com/windows/windowsmedia/drm/default.mspx. DRM gives access rights to digital media content for certified users. These access rights can restrict the number of allowed copies and deny access of uncertified users. The protection is organized with user, content and device dependent encryption techniques.
One problem of DRM is the restriction for users when modifying and copying content they own for their purposes. Different devices need different signal qualities or representations for playing and storing contents. New security paradigms employing a DRM solution for personal private networks of different devices are shown e.g. in Popescu, Crispo, Tanenbaum: “Support for Multi-Level Security Policies in DRM Architectures”, accessible under http://www.cs.vu.nl/˜bpopescu/papers/nspw04/nspw04.html.
One way to make DRM more attractive or acceptable for users is shown in the “Freebies” project of Fraunhofer IDTM, http://www.idmt.fraunhofer.de/eng/research_topics/freebies.htm, where uncertified users have access to one part of the content for advertising purposes. This free part can be shorter than the original, of lower signal quality or include promotion jingles.
However, advanced solutions for encrypting multi-layer audio data are required, ie. audio data that comprise a base layer (BL) and one or more enhancement layers (EL).