Revocation

There are several ways to carry out revocation such that the user is not able to playback the content file. Revocation mechanisms can be as granular as revoking an individual DRM security component or as broad as refusing license issuance to a class of applications. Three such ways are noted below.

• Content Revocation: Content providers can revoke specific content from the user's machine by issuing a license with a content revocation key. The content revocation key is the public key used to sign the header of the content. When a content provider wants to revoke the content, the content provider adds the public key to the revocation list in the license. This feature is therefore enforced by the licensing server.
• Player Application Exclusion: Player exclusion is a feature that allows a license issuer to prevent specific player applications from playing certain packaged files. This feature is enforced on the client by the license. When generating a license for a packaged file, the license issuer specifies the ID for the player application to exclude. The result is that consumers cannot play the packaged file on the excluded player application. The benefit to this feature is that the excluded player application is not affected. It is only prevented from using the packaged files.
• Protected Content Manager Exclusion: Players that work with packaged files contain a Protected Content Manager, which encrypts and decrypts the content and enforces the rights in licenses. Protected Content Manager exclusion is a feature that allows you to identify player applications that are based on a compromised Protected Content Manager. This feature is enforced by the licensing server. Microsoft publishes a Protected Content Manager exclusion list that license issuers must obtain and periodically update. Then, if a license issuer receives a license request from a player that is based on an excluded Protected Content Manager, the license issuer can refuse to issue a license. Instead, the license issuer can display a link for downloading a new player or upgrade.