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What are the copy protection issues?
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5) Content Protection for Recordable Media (CPRM) CPRM is a mechanism that ties a recording to the media on which it is recorded. It is supported by all DVD recorders released after 1999. Each blank recordable DVD has a unique 64-bit media ID etched in the BCA. When protected content is recorded onto the disc, it can be encrypted with a 56-bit C2 (Cryptomeria) cipher derived from the media ID. During playback, the ID is read from the BCA and used to generate a key to decrypt the contents of the disc. If the contents of the disc are copied to other media, the ID will be absent or wrong and the data will not be decryptable.

6) Digital Copy Protection System (DCPS) In order to provide for digital connections between components without allowing perfect digital copies, five digital copy protection systems were proposed to the CEA. The frontrunner is DTCP (digital transmission content protection), Under DTCP, devices that are digitally connected, such as a DVD player and a digital TV or a digital VCR, exchange keys and authentication certificates to establish a secure channel. The DVD player encrypts the encoded audio/video signal as it sends it to the receiving device, which must decrypt it. This keeps other connected but unauthenticated devices from stealing the signal. The first four forms of copy protection are optional for the producer of a disc. Movie decryption is also optional for hardware and software playback manufacturers: a player or computer without decryption capability will only be able to play unencrypted movies. CPRM is handled automatically by DVD recorders. DCPS and HDCP will be performed by the DVD player, not by the disc developer.

These copy protection schemes are designed
only to guard against casual copying (which the studios claim causes billions of dollars in lost revenue). The goal is to "keep the honest people honest." The people who developed the copy protection standards are the first to admit that they won't stop well-equipped pirates.
1) Analog CPS (Macrovision) Videotape (analog) copying is prevented with a Macrovision 7.0 or similar circuit in every player. The general term is APS (Analog Protection System), also sometimes called copyguard. Macrovision adds a rapidly modulated color burst signal ("Colorstripe") along with pulses in the vertical blanking signal ("AGC") to the composite video and S-Video outputs. This confuses the synchronization and automatic-recording-level circuitry in 95% of consumer VCRs. Unfortunately, it can degrade the picture, especially with old or nonstandard equipment. Macrovision may show up as stripes of color, distortion, rolling, black & white picture, and dark/light cycling. Macrovision creates problems for most TV/VCR combos and some high-end equipment such as line doublers and video projectors. Macrovision was not present on early players, but is required on newer players. The discs contain "trigger bits" telling the player whether or not to enable Macrovision AGC. The producer of the disc decides what amount of copy protection to enable and then pays Macrovision royalties accordingly (several cents per disc). Just as with videotapes, some DVD's are Macrovision-protected and some aren't. There are inexpensive devices that defeat Macrovision, although only a few work with the new Colorstripe feature. These devices go under names such as Video Clarifier, Image Stabilizer, Color Corrector, and CopyMaster. APS affects only video, not audio.

Each disc also contains information specifying if the contents can be copied. This is a "serial" copy generation management system (SCMS) designed to prevent copies or copies of copies. The CGMS information is embedded in the outgoing video signal. For CGMS to work, the equipment making the copy must recognize and respect the CGMS information. The analog standard (CGMS-A) is recognized by most digital camcorders and by some computer video capture cards (they will flash a message such as "recording inhibited"). Professional time-base correctors (TBC's) that regenerate lines 20 and 21 will remove CGMS-A information from an analog signal.

3) Content Scrambling System (CSS) Because of the potential for perfect digital copies, movie studios forced a deeper copy protection requirement into the DVD standard. Content Scrambling System (CSS) is a data encryption and authentication scheme intended to prevent copying video files directly from DVD-Video discs. DVD players have CSS circuitry that decrypts the data before it's decoded and displayed. On the computer side, DVD decoder hardware and software must include a CSS decryption module. All DVD-ROM drives have extra firmware to exchange authentication and decryption keys with the CSS module in the computer. Beginning in 2000, new DVD-ROM drives are required to support regional management in conjunction with CSS. Makers of equipment used to display DVD-Video (drives, decoder chips, decoder software, display adapters, etc.) must license CSS. There is no charge for a CSS license. In October 1999, the CSS algorithm was cracked and posted on the Internet.

4) Content Protection for Pre-recorded Media (CPPM) CPPM is used only for DVD-Audio. It was developed to improve on CSS. Keys are stored in the lead-in area, but unlike CSS there are no title keys in the sector headers. A disc may contain both CSS and CPPM content if it is a hybrid DVD-Video/DVD-Audio disc.
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