Security on DVD players


Most DVD-Video titles use Content Scrambling System (CSS) encryption, which is intended to discourage people from making perfect digital copies to another medium or from bypassing the region control mechanism (see below). Discs can also specify that the player use Macrovision, an analog anti-copying mechanism that prevents the consumer from copying the video onto a VCR tape by using a deliberately-defective signal which may also cause problems for some projection TV's as well as older television models. This alone would not prevent the duplication of DVDs in their entirety without decrypting the data, given suitable equipment, although "consumer-grade" DVD writers deny this ability by refusing to duplicate the tracks on the disc which contain the decryption keys.

The CSS system has caused problems for the inclusion of DVD players in strictly open source operating systems, since open source player implementations can not officially obtain access to the decryption keys or license the patents involved in the CSS system. Proprietary software players may also be difficult to find on some platforms. However at least one successful effort has been made to write a decoder by reverse engineering, resulting in DeCSS. This has led to long-running legal battles and the arrest of some of those involved in creating or distributing the DeCSS code, through the use of the U.S. Digital Millennium Copyright Act, on the grounds that such software could also be used to facilitate unauthorized copying of the data on the discs.