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Digital rights management or digital restrictions management, commonly abbreviated DRM, is an umbrella term for any of several arrangements by which the usage of copyrighted data by someone who has purchased a copy of it may be restricted by the copyright holder. Some would like to use DRM mechanisms to protect and proprietary information as well. This latter proposal will raise profound questions in actual practice: claims that this or that is proprietary or a trade secret will be much harder to judge, keep resonable, or prevent misuse of than any claim of copyright. Copyright status is granted by government enactment and is regulated, more or less closely. Claims of proprietary or trade secret status are not. The protected context is most commonly digital (ie, as in a computer or computerized device), hence the 'digital' in DRM; the reason is that the cryptography techniques used and proposed are not directly applicable to analog information.
In contrast to existing legal restrictions which copyrighted status imposes on the owner of a copy of any such data, most DRM schemes would allow additional restrictions to be imposed solely at the discretion of the copyright holder, through hardware and software whose actions are under the copyright holder's control. In the extreme, such control is proposed within other's computers and computerized devices as a 'part' of the operating system. The Trusted Computing Platform Architecture scheme proposed by the Trusted Computing Platform Alliance is an example, as is the Palladium scheme proposed by Microsoft for its future operating systems. (See Professor Ross J Anderson's TCPA / Palladium FAQ for more information on both).
Several laws relating to DRM have been proposed or already enacted in various jurisidictions (State, Federal, non-US). Some of them require _all_ computer systems to have mechanisms controlling the use of digital media. (See Professor Edward Felten's freedom-to-tinker Web site for information and pointers to the curretn debate on these matters).
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 which is no longer marketed. The name is also used (DivX), in ironic tribute to the defunct disk 'protection' scheme, for a video compression protocol, akin to MPEG-4.
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). See Professor Edward Felton's freedom-to-tinker Web site (www.freedom-to-tinker.com) for some observations on the DCMA, its proposed successors, and their consequences, intended and unintended hilarious (www.freedom-to-tinker.com/archives/cat_fritxs_hit_list.html/).
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. See the TCPA / Pallidium FAQ maintained by Professor Ross J Anderson on his Web site at www.cl.cam.ac.uk/~rja14/tcpa-faq.html/ for a clear discussion of two prominent proposals.
Opponents of DRM, as currently envisioned and implemented, note that by delegating computer access (or control of the ability to execute some programs, or to execute programs only with certain data) to third parties, there is a very considerable risk of problems well beyond any control of intellectual property rights issues. For instance, due to a bug (or misdesign, or misadministration of an otherwise 'reasonable' design) the protecting code implementing the local part of a DRM scheme may prevent a computer user from using his computer at all, or from using programs (or using data as an input to a program) when such use is actually completely legitimate and not a violation of any copyright holders' rights. Or, for another instance, a legitimately purchased copy of <a DVD containing a book or a movie, or a software program, or ...> might be blocked because it is being used on equipment which doesn't include the DRM function permitting access to it. Security protocols, software implementing security protocols, and cryptography generally have historically proven extremely difficult to design without vulnerabilities due to bugs or design mistakes. This has been true of designs from experienced and well respected professionals.
Some DRM advocates have suggested (and some legislation has actually been introduced to authorize) that copyright owners be given the ability to remotely delete information from others' computers when, in the view of the copyright holder (or more accurately the copyright holder's software), it is not being legitimately held. The prospect of a bug or maldesign in the software implementing any such scheme is more than a little disturbing to many. They point out that we have demonstrated (by frequent and long extant virus infestation, system software security error, and application software failure) that we don't currently know how to design software that does something specific. How much less likely are we likely to get right software which must do something quite dangerous (ie, file or program deletion, system interference) in only somewhat foreseeable circumstances? Pattern recognition software is not yet fully capable of even distinguishing the predictable (ie, has this <fingerprint, iris pattern, retinal pattern, face, ...) been seen before; it does not seem likely that it will be able to reliably distinguish between <this class of data> and not yet existing documents, parodies, samplings, and so on, especially when the legitimacy of possession or use depends entirely on outside_the_computer facts such as purchaser, terms of purchase, details of license contracts applicable to this particular copy of the <whatever> and this particular situation, and so on.
DRM advocates have taken the position, in essence, that the DRM / security / cryptography design situation is sufficiently well understood and software engineering is sufficiently well practiced that it is possible to achieve the desired ends without causing unrelated problems for users, their computers, or those who depend on either.
Thus far, neither side has compelled the other to agree, though there has been much heat and little enlightenment. Legislation to impose, by force majure, a DRM 'solution' on all is under consideration in many jurisdictions. Some has already been enacted.
One early example of a DRM scheme is that protecting textbooks required in some US Dental Schools. The textbooks are available only on CD, and are readable in a computer only for a limited time, after which the CD 'expires' and the information in the 'book' is lost. Some of these books are not available on paper at all. Those who still have their college or graduate school texts might find this quite surprising. Dental students whose textbooks have evaporated may be expected to be somewhat different as dentists than their predecessors whose instructional materials were less evanescent.
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 by criminals as a means of preventing enforcement of laws against fraud and other wrongdoing. Since DRM is unlikely to be so used by individual criminals, only corporate skullduggery is likely to be concealed this way.
See also: copy protection