Traditional copyright protections (such as infringement lawsuits) are suitable only in specific cases and are impractical on a mass scale. They would be entirely useless against the millions of people who might buy DVDs and copy them for their friends and relatives. Therefore, much of the consumer-electronics equipment available today incorporates copy-protection mechanisms. Different types of devices use different kinds of copy protection. Most techniques stem from cooperation between content providers and equipment manufacturers. For DVI, such a cooperative effort has produced a mechanism called HDCP (high-bandwidth digital-content protection), a two-part cryptographic method to control video delivery.

Bookmark for me. Nice overview of HDCP. Basically, a secure pipe to transmit content between a device and an output (ie computer to monitor, DVD to TV, etc). To protect against piracy.