With the invention of CD-R, CD-RW, and DVD-R devices, copy protection has become a big issue to prevent the duplication of disks.

DVD Regional Codes
DVD regional codes are used to make sure that DVD's are only functional is certain areas of the world. Because movies and computer games are released at different times to different parts of the world, it is important that DVD's are not able to be played everywhere. Many movies are already out on DVD in North America by the time that they are just being released to the movie theaters in Europe, and vise versa. DVD regional encoding is to ensure DVD's aren't in places that they are not suppose to be. There are 6 different DVD regional zones,

1. Canada, U.S., U.S. Territories
2. Japan, Europe, South Africa, Middle East (including Egypt)
3. Southeast Asia, East Asia (including Hong Kong)
4. Australia, New Zealand, Pacific Islands, Central America, Mexico, South America, Caribbean
5. Former Soviet Union, Indian Subcontinent, Africa (also North Korea, Mongolia)
6. China

DVD regional encoding isn't a real encryption scheme, it is a single byte stored on the disk which is always read by the DVD device. Each DVD device has their own regional number, and the two numbers have to be the same in order for the disc to play. The DVD device's numbers are set by the manufacturer depending on the region the device is sold to. DVD regional numbers are made to be permanent, but there are many ways which they found out to be able to change this number. Newer drives allow this number to be changed between 5 and 8 times, but after that limit is reached the number is permanent.

Analog CPS - Macrovision VCR Protection
DVD's and video tapes hold movies, which could easily be duplicated by recording the video signal with a VCR. A company called Macrovision invented an Analog Protection System (APS) that will protect against this. All video cards capable of video output must be able to use APS, along with all VCR's. APS works by rapidly changing the colourburst signal ("colorstripe") along with pulsating the vertical blanking signal. This will confuse the synchronization and automatic recording level circuitry in almost all VCR recorders. This technique is transparent during playback, except in some older VCR equipment and televisions which use line doublers. In the incompatible hardware, this can cause serious video distortions.

For DVD discs, the disc header contains "trigger bits" for each sector telling the video decoder whether or not Macrovision was encoded into the video. The producer of the disc can decide which portions of the disc has a need for copy protection, because all video that uses Macrovision encryption has to to pay royalties on a per minute basis. Because of the royalties, not all DVD's or videos use this encoding.

Content Scrambling System
CSS is used exclusively in DVD video to prevent DVD video files from being able to be copied. It is a means in which files are unplayable without a specific 5-byte (40bit) key. This key is used in a specific way as defined by CSS to decrypt the information into a useable form. Decryption hardware or software, and in order for the makers of the hardware or software to know what the key is, they had to go through a lengthy non-disclosure agreement in order to licence the technology ad obtain their key which they would use for decoding. Part of this licencing is that the company is not able to have there product duplicate the files or output the decrypted data to a device that can.

Recently, a Norwegian group Masters of Reverse Engineering (MoRE) decoded the key from a faulty software DVD player called Xing DVD. Because of this, source code for the key has been published on the Internet, and a program named DeCSS, which is a small 60KB application is being distributed that is capable of decoding CSS on its own. Because they key was found out to be only 5 bytes long, through trial and error, the makers of DeCSS have found over 170 other valid keys from other companies.

Storage Mediums and Devices | CD Formats | Disk Copy Protection