Digital videodisks provide an example of hardware-based copy protection for special-purpose devices used by the entertainment industry.  Developed by studios and consumer electronics companies in late 1995, digital videodisks (DVDs) are used in the entertainment industry to distribute movies and other content. DVDs are compatible with CDs and are of the same size and thickness as CDs, but they have much more capacity--up to 25 times as much as a CD.

Content  on a DVD is protected by a variety of mechanisms:

 ¬      Data on the DVD is encrypted using a system called the content scrambling system (CSS).

 ¬      Each disk indicates whether the contents can be copied, enabling serial copy management. For example, a device getting information from a disk marked "one copy" must change the information on its version to indicate "no [more] copies."

 ¬      The DTCP protocol is used to encrypt information for transmission from the DVD player to other devices.

 ¬      Analog copy protection is inhibited by a Macrovision circuit; this adds a signal to the analog video output that will (typically) not distort the display of the video but will cause a recording device to record a significantly degraded copy. This inhibits copying DVDs to videotape.

The DVD technical protection system is useful for keeping honest people honest, but from a security point of view it has had defects in its design that have prevent ed it from being a major deterrent for skilled pirates. In November 1999, the CSS encryption scheme was broken, and consequently CSS has not been adopted elsewhere.