DRM—Digital Rights Management to its advocates, Digital Restrictions Management to its detractors—seems to be added to all forms of media these days. It’s usually billed as an anti-piracy mechanism, but in reality it comes down to control. Copy protection, the predecessor to DRM, was intended to control illegal copying. DRM expands on this strategy by attempting to control what you can do with media. This extends the rights granted by copyright beyond exclusive distribution to regulation of use.
How DRM Works
At its heart, DRM is a cryptographic system. The medium protected by DRM must be encoded in some way to prevent it from being played without the consent of the DRM system. In practical terms, this means that it must be encrypted. A traditional cryptographic system involves sending a message from one person to another without an attacker being able to intercept the message. In the case of DRM, the recipient of the message and the attacker are the same person. As you can imagine, this arrangement presents some difficulties for designers of DRM systems. The most common solution is to require a closed system.