Monday, July 2, 2012

The right protection for DVD - part 2 - Copy Protection

DVD copyright protection has set with two measures the region codes and copy protection.


In order to protect the copy right, CPTWG of DVD forum offers a kind of CSS to protect the content of DVD.It is possible to prevent copying by setting a key.But copy may happen on the point of signal transmission. So, , Hitachi, Intel, Panasonic, Sony, Toshiba and other companies to five digital transmission copy protection (DTCP); IBM, NEC, Hitachi, Pioneer, Sony Group and the Milky Way consisting of Macrovision, Digimarc, Philips formed the Millennium Group of video watermarking technology; IBM, Intel, Matsushita, Toshiba and other four companies to copy protection system, its content: CPSA (content protection system Association), CPRM (for the recordable media content protection), CPPM ( for the pre-recorded media content protection). 

Content Scramble System (CSS) is a kind of security solution that is used to prevent copying files directly from DVD disc data with encryption and authentication program. CSS certificate has a key for each certificate, which is stored in each CSS encrypted disc which is drew from the master concentration with 400 key components. After the key is removed, the certificate shall be invalid. CSS decryption algorithm exchanges keys with the drive unit to generate the set encryption key. The generated key is used to disrupt the disc with the movie key exchange key. Video key is used to decrypt the data on the disc. The DVD player shall decrypt the data with the CSS circuit. If it is the computer, the DVD decoder hardware and software must include a CSS decryption module. All DVD-ROM drive has an extra device can exchange authentication and decryption keys with computer CSS systems. In order to use CSS, producers that made DVD video devices (drives, decoder chips, decoder software, display adapters, etc.) must certify the CSS. Verification of CSS shall be of no cost. To ensure the confidentiality of CSS algorithms and keys, the certificate is extremely stringent. Of course, so many people around the world players and drives, nothing can ever be secret. In October 1999, CSS algorithm was cracked Norwegians, and was spread on the Internet, after stop. 

Watermark Identification

Watermark Identification is to set each digital audio or video frames with noise that the human eye or ear are unaware of. Playback and recording device can identify the watermark label to prevent copying. The new players and other devices will support the watermark, but the DVD Forum intends to make watermarked discs compatible with existing players. 


CPRM will be media and recording-related. Each blank recordable DVD disc has a 64-bit disc ID placed in the BCA (Burst Cutting Area Group engraved area). When the protected content is burned to disc, the disc ID, it can obtain 56 C2 (Cryptomeria) password for encryption. During playback, the BCA is read the disc ID, and then generate the disc key needed to decrypt the content. If the disc content from being copied to other media, the disc ID will be lost or error, the data will not be able to decrypt.


CPPM is only for DVD-Audio. Key is placed in the lead in area, but there is no title key in the sector head. Disc key is replaced by "album identifier". The identification solutions are the same for both program and CSS, so the existing equipment will not have any modifications. Disc can contain both CSS and CPPM content. 

Copy protection also includes ACPS, CGMS, and DCPS and so on. 


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