The BD+ is a Virtual Machine-based technology dedicated to BD Format. Together with the RomMark, they are the additional elements of the Blu-Ray Disc Format added to protect HD content stored on Blu-Ray media.
BD+ relates to the ability to keep content from playing on a known hacked player, and is an additional weapon of the AACS/Blu-Ray Disc Association against movie piracy. Implementation of BD+ is required for BD-ROM movie players and BD-ROM game consoles (PS3 for now) and BD-ROM PC Application Software.
The BD-ROM players include a small Virtual Machine to provide a basic processing environment for BD+ Content Code. In addition, the VM allows Studios to optionally include Title-specific BD+ Content Code on the Disc.
During reproduction of a BD-ROM title, the VM runs the Content Code to apply the Security Check and enable content playback when the player is legitimate. A security code runs continuously during playback in order to correct the corrupted stream and produce viewable content.
When a hack is suspected, content provider can enter into a hack study. Once a hack is confirmed by the manufacturer of suspected Player, then Content Provider can have developed and release BD+ Content Protection code that detects and responds to the hack.
In addition, BD+ includes the ability to load native code (code that runs directly on the player's host process). It is allowed to deploy it only after it is proven that basic countermeasure code cannot address the hack.