BD+ is an interpreter mechanism or virtual-machine-based technology designed for BD-ROM disc security. BD stands for Blu-ray Disc (also known as Blu-ray) and is a type of optical storage media having the same dimensions as the standard CD. Blu-ray Disc was developed by the Blu-ray Disc Association. Blu-ray Disc uses a blue-violet laser unlike standard DVD, which uses a red laser. Blue laser has a much shorter wavelength and can thus be used to store much more data than a DVD.

BD+ is essentially a mechanism or security technology that is included on BD-ROM discs as a security layer on the discs. It has been defined as the DRM protocol that is used to protect Blu-ray discs. Digital rights management (DRM) refers to restriction technologies used by publishers and copyright holders to limit usage of digital media or devices. BD+ provides some sort of defense for the discs by acting as a security response system. BD+ will react to security attacks, but will not necessarily prevent them completely. BD+ therefore takes Blu-ray one step further by giving Blu-ray an additional layer of anticopy technology.

BD+ uses a small virtual machine environment to ensure conformity, making it a very sophisticated protocol to use. The small virtual machine launches when a Blu-ray disc is inserted. It then runs in the background while the disc is playing, keeping the disc’s content protected. If it finds evidence of copying, playback can be disabled. Once the disc is ejected, all the code is erased from memory. Each disc has code that is specific to it. This makes it even more difficult to crack. The end result is an extra layer of protection in addition to the AACS encryption used by both Blu-ray and High-Definition Digital Versatile Discs (HD DVD), which was cracked back in April. It has therefore been considered a very difficult encryption scheme to crack even in comparison to HD DVD. In July 2007, Richard Doherty of the Envisioneering Group (BD+ Standards Board) declared: “BD+, unlike AACS which suffered a partial hack last year, won’t likely be breached for 10 years.” Sony also echoed the same opinion. However, some developers claim that BD+ copy protection may have praised a bit too early. In March this year, Slysoft announced that it had cracked the BD+ layer. The company claims that with the release of version 6.4.0.0 of AnyDVD HD, it is now possible to make backup security copies of Blu-ray discs protected with BD+.

The BD+ Standards Board is not exactly worried about this. This is because the BD+ scheme is designed to be dynamically updated. It also allows for some sort of dynamic encryption. BD+ security code is under continuous development to ensure that BD+ customers obtain updated value by using this technology. The dynamic encryption provided means that if the security layer was cracked, then developers would simply need to change the encryption scheme on new BD-ROM discs. This would prevent any other BD-ROM discs from being opened. BD+ technology is therefore relatively safe and unlikely to be breached in the near future.