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Digital rights management or digital restrictions management, commonly abbreviated DRM, is a system whereby the usage of copyrighted data by someone who has purchased a copy of it may be restricted by the copyright holder. In contrast to the usual legal restrictions which copyright itself imposes on the owner of a copy of such data, DRM would allow additional restrictions to be imposed solely at the discretion of the copyright holder, through hardware and software code under the copyright holder's control.
An early example of a DRM system is the Content Scrambling System (CSS) employed by the DVD Consortium on movie DVD disks. The data on the DVD is encrypted so that it can only be decoded and viewed using an encryption key, which the DVD Consortium kept secret. In order to gain access to the key, a DVD player manufacturer would have to sign a licence agreement with the DVD Consortium which restricted them from including certain features in their players such as a digital output which could be used to extract a high-quality digital copy of the movie. Since the only hardware capable of decoding the movie was controlled by the DVD Consortium in this way, they were able to impose whatever restrictions they chose on the playback of such movies. See also DIVX for a more draconian and less commercially successful variation.
The Digital Millennium Copyright Act was passed in the United States in an effort to make the circumvention of such systems illegal. Despite this law, which has received substantial opposition on constitutional grounds, it is now relatively easy to find DVD players which bypass the limitations the DVD Consortium sought to impose. The cryptographic keys themselves have been discovered and widely disseminated (see DeCSS).
New DRM initiatives have been proposed in recent years which could prove more difficult to circumvent, including copy-prevention codes embedded in broadcast HDTV signals and the Palladium operating system. A wide variety of DRM systems have also been employed to restrict access to eBooks.
Examples of existing "digital rights management" and "copy protection" systems:
DRM and document restriction technology
Opponents of DRM have noted that the proposed use of some DRM schemes to restrict the ability to copy and distribute documents can be used as a way of preventing the enforcement of laws against fraud and other corporate wrongdoing.
See also copy protection.