Let's say Jane has only downloaded three files so far this month, so this download is within her subscription rights. And let's say she received a promotional offer for $1 off next month's subscription fee if she downloads this song. Jane should be able to copy the file under fair use, but maybe she can only make three copies. And let's say the copyright holder denies anyone the right to excerpt its digital content. The DRM structure for this download might look something like this:
Keep in mind that while the user status stays the same each time Jane logs on to the site, the relationship between the user, the content and the rights can change. The DRM scheme must be able to adapt to changing conditions. If Jane increases her subscription level to one that allows unlimited downloads instead of only five downloads per month, the DRM software has to adjust to that new relationship. The DRM scheme has to be tied in to the Web site's technology so it can adjust the relationship on the fly. This is one reason why seamless DRM setups are difficult to implement: With no standards to go on, digital rights management software doesn't easily blend in with existing e-commerce tools. Still, arguably the easiest transaction to control is a download from a Web site. The hard part is controlling what a user does with digital content once it's in his or her possession. How is the download site going to enforce Jane's usage rights? How do they know she's only going to make two copies of the file? This is where DRM can get sticky.If you're a big media company trying to keep people from copying electronic material, it's not hard to do.
Companies like ContentGuard, Digimarc, InterTrust and Macrovision sell automated "DRM solutions" that include everything you need to set up a DRM scheme. ContentGuard's complete DRM toolkit lets copyright holders create and enforce licenses for their digital products and services, including everything from movie downloads to software use to Web-site access. The RightsExpress software uses the MPEG REL rights-expression language and guides the copyright holder through the process of defining a piece of content, defining a user and defining usage rights. The copyright holder can set access levels and encryption modes for the content, create a custom interface that lets users obtain content based on those settings, develop an enforcement model that verifies user identification and track the use of that content.