You can try OMA DRM to protect the content.It governs how content is used and allows the development of new end-user features and new kinds of mobile content services for content providers, service developers, operators and service providers. OMA DRM is a Digital Rights Management standard published by the Open Mobile Alliance
By implementing OMA DRM, service providers can allow end users to preview content before making a purchase decision. OMA DRM also supports recommending of great content to other end users via superdistribution.
More info about DRM&Download can be found at http://www.forum.nokia.com/main/1,6566,1_41,00.html#