DVD Copyright Protection Types |
Region Code (RC)
The commercial DVD player specification requires that a player to be sold in a given place not play discs encoded for a different region (region 0 discs are not restricted). The purpose of this is to allow motion picture studios to control aspects of a release, including content, release date, and, especially, price, according to the region. Many DVD players are or can be modified to be region-free, allowing playback of all discs.
Region Code Enhanced (RCE)
However, it is easy to work around the scheme. A region-free player tries to play a disc using the last region that worked with the previously inserted disc. If it cannot play the disc, then it tries another region until one is found that works. RCE could thus be defeated by briefly playing a "normal" region 1 disc, and then inserting the RCE protected region 1 disc, which would now play. RCE caused a few problems with genuine region 1 players. As of 2007, many "multi-region" DVD players defeat regional lockout and RCE by automatically identifying and matching a disc's region code and/or allowing the user to manually select a particular region. Some manufacturers of DVD players now freely supply information on how to disable regional lockout, and on some recent models, it appears to be disabled by default. Programs such as DVD Shrink are also capable of removing RCE protection, provided the operator knows what the region of the disk actually is. If the region is specified correctly, the copy will play in any region.
Analog Protection System (APS)
APS can be also signaled digitally, in the CGMS-A bit field sent in the vertical blanking interval.
Content Scramble System (CSS)
The CSS key sets are licensed by the DVD Copy Control Association to manufacturers who incorporate them into products such as DVD movie releases, drives & players. Most DVD players are equipped with a CSS Decryption module. CSS key is a collective term for authentication key, disc keys, player keys, title keys, secured disk key set, and/or encrypted title keys. Some of the keys are stored on the lead-in area of the disk, which is generally only read by compliant drives. Keys can be passed from a DVD drive to a descrambler over a PC bus using a secure handshake protocol. The purpose of CSS is twofold. First and foremost, it prevents byte-for-byte copies of an MPEG stream from being playable since such copies will not include the keys that are hidden on the lead-in area of the protected DVD disk. Second, it provides a reason for manufacturers to make compliant devices, since CSS scrambled disks will not play on noncompliant devices. Anyone wishing to build compliant devices must obtain a license, which contains the requirement that the rest of the copy-protection system be implemented. In October 1999, Jon Lech Johansen and two people who remained anonymous reverse engineered the algorithm and DeCSS was released. The CSS algorithm was soon revealed to be easily susceptible to a brute force attack, apart from being an example of the trusted client problem. The weakness of the protection is primarily due to US government crypto-export regulations, which, at the time, forbade the export of cryptosystems employing keys in excess of 40 bits - a key length that had already been proven to be wholly inadequate in the face of increasing processing power by the time DVD was released (see DES). In addition, structural flaws in the algorithm reduced the effective key length to only around 16 bits, which could be brute-forced by a 450 MHz processor in less than a minute. As a 450 MHz processor was the stated minimum necessary to decompress a DVD-compliant MPEG-2 videostream in realtime, it effectively meant that any computer that could play a DVD could also crack one. The CSS algorithm has been superseded by the Cryptomeria cipher in newer DRM schemes such as CPRM/CPPM, or by AES in the AACS copy-protection scheme used by HD DVD and Blu-ray Disc.
User Operation Prohibition (UOP)
Some DVD players ignore the UOP flag, allowing the user full control over DVD playback. Virtually all players that are not special-purpose DVD player hardware (for example, a player program running on a general purpose computer) ignore the flag. There are also modchips available for some standard DVD players for the same purpose, although modifying a device may be illegal in some countries. The UOP flag can be removed in DVD ripper software such as: DVD Decrypter, DVD Shrink, AnyDVD, MacTheRipper and K9Copy. Nevertheless, removing UOP does not always provide navigation function in the restricted parts of the DVD. This is because those parts are sometimes lacking the navigation commands which allow skipping to the menu or other parts of the DVD. This has become more common in recent titles, in order to circumvent the UOP disabling that many applications or DVD players offer. UOPs are also used for usability purposes, especially in interactive DVD content. The Next Cell, Previous Cell, and Resume features are often disabled during menus, for instance, to avoid confusing or unintended jumps between content items. DVD Games like "Scene It?" are another example of complex DVD programming in which UOPs are said to ensure a more enjoyable user experience.
Sony ARccOS Protection
RipIt for the Mac, Slysoft's AnyDVD, Fengtao's DVDFab Decrypter, RipIt4Me + DVD Decrypter, FixVTS, DVD43, MacTheRipper, along with VLC media player, GNU ddrescue, dd_rescue and MPlayer/MEncoder (for Linux) are usually able to overcome ARccOS. ARccOS had reportedly been discontinued by Sony in February 2006. However, several high-profile releases since then have used it, including the region 1 DVDs for Hostel, Underworld: Evolution, Running With Scissors, and Casino Royale. Many DVDs by Disney, Touchstone Pictures, and The Weinstein Company also use ARccOS including Pirates of the Caribbean: Dead Man's Chest, Cars, Flightplan, The U.S. vs. John Lennon, Lucky Number Slevin, and Ratatouille. Hairspray appears to also be encumbered with ARccOS. Many DVD rental companies are now warning users that the Sony DVDs in question may not play on their machines. Despite being promoted as "fully compatible with available DVD players and drives," movies with ARccOS cannot be played on some DVD players: Sony DVPCX995, Toshiba SD4700, Harman Kardon DVD101, Microsoft Xbox and others. Sony has announced a future firmware update for their players to fix this incompatibility issue. One revision of the ARccOS scheme used by Sony was incompatible with a higher number of players than average. Sony has offered to replace those discs for owners having problems; the replacement discs will have a newer version of ARccOS coding on them, which Sony claims is more compatible.
Analog CPS (Macrovision)
The general term for a system that prevents taping is APS (Analog Protection System), also sometimes called copyguard. Computer video cards with composite or s-video (Y/C) output must also use APS. Macrovision changes the composite video and s-video output in two ways: the Colorstripe technique creates a rapidly modulated colorburst signal, and the AGC technique inserts pulses in the vertical blanking signal. 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 was not present on analog component video output of early players, but is now required on component output (AGC only, since there is no burst in a component signal). The discs themselves contain "trigger bits" telling the player whether or not to enable Macrovision AGC, with the optional addition of 2-line or 4-line Colorstripe. The triggers occur about twice a second, which allows fine control over what part of the video is protected. 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 DVDs are Macrovision-protected and some aren't. (For a few Macrovision details see STMicroelectronics' NTSC/PAL video encoder datasheets at <www.st.com/stonline/books/>.) Inexpensive devices can defeat Macrovision, although only a few work against the more recent Colorstripe feature. These devices go under names such as DVD Red, Video Clarifier, Image Stabilizer, Color Corrector, DVD Red, and CopyMaster. Or you can build your own. Some DVD players can be modified to turn off Macrovision output (see 6.4.2). Professional time-base correctors (TBCs) that regenerate line 21 also remove Macrovision. APS affects only video, not audio.
CGMS
Content Protection for Prerecorded Media (CPPM)
Content Protection for Recordable Media (CPRM)
Digital Copy Protection System (DCPS)
High-Bandwidth Digital Content Protection (HDCP, DVI, and HDMI)
HDCP provides authentication, encryption, and revocation. Specialized circuitry in the playback device and in the display monitor encrypts video data before it is sent over the link. When an HDMI output senses that the connected monitor does not support HDCP, it lowers the image quality of protected content. The HDCP key exchange process verifies that a receiving device is authorized to display or record video. It uses an array of forty 56-bit secret device keys and a 40-bit key selection vector -- all supplied by the HDCP licensing entity. If the security of a display device is compromised, its key selection vector is placed on the revocation list. The host device has the responsibility of maintaining the revocation list, which is updated by system renewability messages (SRMs) carried by newer devices and by video content. Once the authority of the receiving device has been established, the video is encrypted by an exclusive-or operation with a stream cipher generated from keys exchanged during the authentication process. If a display device with no decryption ability attempts to display encrypted content, it appears as random noise. Introduction to Any DVD Shrink Any DVD Shrink is a powerful DVD copy and burning software, which can decode and clone copy-protected movie DVD and non-protected DVDs for you for storage and collections, or burn ISO image and DVD folder on hard drive to DVD and burn DVDs among different DVD discs. It enables you to copy you movie DVDs to hard drive in dvd folder or ISO image file formats, or clone DVD movies from one dvd disc from anther one, even compress DVDs automatically when necessary. It is so easy to use, backup your costly DVDs within a few clicks. |