微软避免DRM Component被滥用的一种方式

下面内容摘自 Windows Media Rights Manager 9 Series SDK 文档

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Refusing Licenses to Excluded DRM Components

To ensure that licenses are not issued to player applications using DRM components known to be damaged or corrupted, Windows Media Rights Manager SDK posts a DRM component exclusion list that you must install on the computer running Windows Media License Service . This exclusion list contains the public keys of those DRM components known to be damaged or corrupted.

The license issuer can detect when a license request is coming from a player using an excluded DRM component, and refuse to issue the license. The license issuer can also display a Web page where the consumer can install a new player or upgrade their current player to a version that is acceptable.

To detect whether a license request is coming from a player using an excluded DRM component, use the WMRMLicGen.IsClientExcluded property. Revoking players by using revocation lists is similar, except that rather than preventing a consumer's player from playing any packaged files (including ones that were acquired before the player was revoked), refusing a license to a player with an excluded DRM component simply prevents the consumer from playing new packaged files on the player. The player itself is not affected.

To install the latest DRM exclusion list for each computer that runs Windows Media License Service (licensing server), go to the Microsoft Web site http://licenseserver.windowsmedia.com/, and then click Download the latest License Service Information. It is recommended that you automate this process to occur periodically.

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文章有这样一句： those DRM components known to be damaged or corrupted，我理解它的意思是“那些已损坏或被滥用的DRM组件”，也是不怀好意的DRM组件。

看来，微软定期会整理、更新一份DRM组件排除清单（exclusion list），清单的内容是那些已被破坏的DRM组件的Public Key 列表，这份清单随 License Service Information发放，每个内容发行商都可以定期下载这份清单并应用在自己的许可证服务器上。发放许可证时，License Generator 会自动把排除清单写入许可证，这样就可以避免那些使用被破坏DRM组件的恶意播放器打开、破解、复制自己的受保护内容了。