However, he did not release any source code in fear of a Microsoft lawsuit regarding possible violation of the DMCA. This would allow digital content to be played on equipment that does not implement DRM restriction measures (like rescaling of video resolutions and disabling analog audio outputs). In January 2007 the developer Alex Ionescu announced that he had found a method that allows end users to bypass Vista's Protected Media Path. It is complementary to PVP Output Protection Management. However, rather than being a software application programming interface, PVP-OPM operates with the Windows media components in the protected environment.Īdditionally, PVP-UAB (Protected Video Path - User-Accessible Bus) is used to encrypt video and audio data as it passes over the PCI-Express bus, to prevent it from being intercepted and copied on the way to the graphics card. In Vista, the control of PC video outputs is provided by PVP-OPM, which is essentially the next generation of Certified Output Protection Protocol (COPP) introduced in Windows XP. Some output types such as S/PDIF (Sony/Philips Digital Interchange Format) typically don't have a suitable DRM scheme available, so these need to be turned off reliably if the content so specifies. Users' standard unprotected content will not have these restrictions. These restrictions only apply to DRM-restricted content, such as HD DVD or Blu-ray that are encrypted with AACS, and also apply in Windows XP using supported playback applications. Even analog TV-style outputs typically require some restrictions, provided by mechanisms such as Macrovision and CGMS-A. For DRM content, digital outputs such as Digital Visual Interface (DVI) and High Definition Multimedia Interface ( HDMI) will have High-bandwidth Digital Content Protection (HDCP) enabled, to prevent someone from recording the digital stream. These restrictions concern the various outputs from the PC. The protected environment is implemented completely in software, so software-based attacks such as patching the Windows kernel are possible. If an unverified component is detected, then Vista will stop playing DRM content, rather than risk having the content copied. In order to prevent users from copying DRM content, Windows Vista provides process isolation and continually monitors what kernel-mode software is loaded. It provides a "wall" against outside copying, where within the walls, content can be processed without making the content available to unapproved software.
The protected environment also provides all the necessary support for Microsoft-approved ( signed) third-party software modules to be added. The protected environment in which DRM content is played contains the media components that play DRM content, so the application only needs to provide remote control (play, rewind, pause, and so on), rather than having to handle unprotected content data.
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