What is DRM?

Digital Rights Management, or DRM, is a class of technologies that allow rights owners to set and enforce terms by which people use their intellectual property.

Rights owners are typically copyright-holding companies like music, film, book or software publishers. They use DRM to control how documents, entire software programs, or even e-mails are used.

Most often media companies use DRM to curb piracy of their content by restricting users' ability to copy it, though it can also be used to create new business models like subscriptions to a large library of music.

How does DRM work?

DRM is a two-part scheme. It relies on encryption to protect the content itself and authentication systems to ensure that only authorised users can unlock the files.

When applied, DRM scrambles the data in a file rendering it unreadable to anyone without the appropriate unlocking key.

Authentication systems stand between users and the decryption keys, ensuring that only people with the proper permissions can obtain a decryption key.

Without a username and password or if a file has been decrypted too many times, the system will not provide the key. This means music files with DRM, for example, can be swapped over the internet and remain unusable to those who have not paid for them.

It also means only authorised programs and portable players can use the tracks.

Music without DRM, like the popular MP3 music format, retain the ability to be played regardless of the number of times or to whom they have been copied.

Who is using DRM and why?

The most common commercial use of DRM is copy prevention. The technology gives rights holders some assurance that their intellectual property will not be pirated, and helped to create a legal digital download industry.

Film studios were some of the first large companies to adopt DRM.

When the DVD format was launched it included an encryption scheme called the Content Scrambling System, which prevented users from making digital copies of films off the disc.

Recording labels have also adopted DRM to prevent copying.

With the advent of peer-to-peer file sharing networks and the MP3 music compression format in addition to the proliferation of broadband internet access, they claimed music piracy drastically increased.

CD publishers reacted by making discs in a way that lets them play in a regular machine, but not in a computer. This prevents users from copying the music and distributing it over the internet.

Many record labels have also released DRM-protected music for sale and download in online stores like Apple's iTunes and Roxio's Napster. These tracks can play on a set number of computers and portable devices.

DRM video downloads are just beginning in the UK. Channel 4 and Sky have on-demand services that include films.

What are the problems with DRM?

Some consumer groups and internet commentators vociferously argue against the use of DRM.

One of the most often cited problems with the technology is that competing systems are not compatible. For example, users of the Napster service cannot play a track on the iPod.

Changing music download providers or portable players could mean already purchased tracks are unusable.

Because tracks have to be authenticated to play, they may also become unusable if a download company goes out-of-business.

Both cases force purchasers to either forfeit their music or re-purchase it, and for this reason has been characterised as anti-competitive.

Unlike brick-and-mortar shops selling records, cassettes, or CDs, digital download companies can lock consumers into their service.

Critics also argue that many DRM systems go far beyond the rights the law gives rights holders to protect what they create.

DRM is also an imperfect technology. Hackers and software companies engage in a constant back-and-forth battle where any given system is broken, patched, and broken again.

DVD copy prevention was cracked in part by the then 15-year-old Jon Lech Johansen.

Still others object to DRM on philosophical grounds. Art, they contend, is often a collaborative process that builds off the work of others.

For digital media, this is referred to as the "rip, mix, burn" culture.

As music, film, and literature is increasingly expressed in digital form, many worry that restrictions on the use of this content will limit creativity.