Cactus Data Shield (CDS) is a form of
CD/DVD copy protection CD/DVD copy protection is a blanket term for various methods of copy protection for CDs and DVDs. Such methods include DRM, CD-checks, Dummy Files, illegal tables of contents, over-sizing or over-burning the CD, physical errors and bad sectors. M ...
for audio
compact disc
The compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then released in Oc ...
s developed by
Israel
Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
i company Midbar Technologies. It has been used extensively by EMI (subsequently acquired by
Sony Music
Sony Music Entertainment (SME), also known as simply Sony Music, is an American multinational music company. Being owned by the parent conglomerate Sony Group Corporation, it is part of the Sony Music Group, which is owned by Sony Entertainme ...
) and BMG and their subsidiaries. CDS relies on basically two components: Erroneous Disc Navigation and Data Corruption.
As of September 2006, all of Macrovision's CD copy protection products, including CDS, had quietly disappeared from their website. The December 2006 issue of
Billboard announced that EMI had decided to abandon Copy Control worldwide.
Erroneous Disc Navigation
CDS discs contain an initial audio session, similar to that of an unprotected disc. In addition the disc contains a second (data) session and a software player configured for auto-play with a lower-quality, compressed version of the audio for it to play.
The second session on the disc causes some CD/DVD players to hang, typically some car players (allegedly using CD-ROM drive mechanisms) and some MP3 capable players that can see but not understand the second data session.
The second session has been circumvented by another method, which is to either place
masking tape around the disc near the edge, or mark a strip next to the edge with permanent marker. Because it is a multi-session disc, this method will hide the second session, leaving only the first audio session visible. This trivial circumvention of Macrovision's copy protection allows protected CDs to be copied using CD-ROMs or played in CD players that struggled to understand CDS multi-session discs.
On older Windows operating systems, disabling auto-play either once when loading the disc, or permanently, can stop the software player from launching and may be all that is required to access the audio session for drives that recognise both sessions. Newer versions of Windows since Vista have fixed the auto-run vulnerability thus all the user needs to do is simply choose not to run the software.
A side effect of the second session containing the music in compressed form is that the maximum length of music on a CDS disc is reduced, being approximately 70 minutes. The remaining space is use for the compressed audio (and the player software and other files though these are small by comparison).
Data Corruption
The second aspect of Cactus Data Shield is careful corruption of the audio data, as described in the Midbar patent "Prevention of disk piracy" US patent number 6,425,098. As usual for patents this is freely available on the
US Patent Office
The United States Patent and Trademark Office (USPTO) is an agency in the U.S. Department of Commerce that serves as the national patent office and trademark registration authority for the United States. The USPTO's headquarters are in Alexa ...
web site.
In summary the method described detects during mastering when the waveform of the music comes close to being a straight line for at least the size of a "frame" (information on the disc is encoded in blocks or sectors, each sector contains 98 frames of music for a CDDA disc) and marks the frame and replaces it with erroneous data that violates the T.sub.max (according to the IEC 908) in which there is no transition between the high and low data levels (1 to 0 or 0 to 1). This results in a DSV (Digital Sum Value) error on the CD.
Additional data corruption described in the patent includes adding a duplicate entry of the TOC (Table of contents) from the audio session onto the second (data) session. Some older CD drives would only see the second session erroneous values (such as time and track type) and were not able to copy or play these. Another method is to change the start time of the Lead-Out (end of the disc) to an incorrect time in the TOC. Other patent processes include changing the time in the Q channel so it holds, speeds up or flows backwards.
Interpretation of Corrupted Data
An old-fashioned
CD player
A CD player is an electronic device that plays audio compact discs, which are a digital optical disc data storage format. CD players were first sold to consumers in 1982. CDs typically contain recordings of audio material such as music or audio ...
reading subcode correctly sees a missing audio frame and
interpolates any missing information that it cannot correct using information from neighbouring frames. Because these missing frames occur at points where the waveform was nearly a straight line anyway, this interpolation is very accurate and generally
transparent
Transparency, transparence or transparent most often refer to:
* Transparency (optics), the physical property of allowing the transmission of light through a material
They may also refer to:
Literal uses
* Transparency (photography), a still, ...
to the user.
What happens with computer drives is very specific to the hardware and
firmware of the drive in question, assuming they have at least seen past the second data session and can play the audio session.
Some older drives simply ignore the subcode and "play" the data frames, resulting in loud audio glitches. Some are overwhelmed by the number of errors needing correction and interpolation, and these drives may then output occasional glitches.
Ripping
Ripping is extracting all or parts of digital content from a container. Originally, it meant to rip music out of Commodore 64 games. Later, the term was used to extract WAV or MP3 format files from digital audio CDs, but got applied as well to e ...
at the drive's minimum speed can reduce or eliminate this effect.
The majority of new drives can successfully correct and interpolate all missing audio even at maximum ripping speeds.
Impact
The techniques used on Cactus Data Shield discs mean the discs do not conform to the
red book Compact Disc Digital Audio standards, and they therefore do not bear the Redbook logo. For this reason they should not be referred to as CDDA (Compact Disc Digital Audio).
There are also ethical/legal issues surrounding the selling of discs that won't reliably play in all players, where added errors make the disc more easily affected by accumulated lifetime damage, and where actual audio data has been omitted.
One of the earliest released CDs utilizing copy-protection was ''
White Lilies Island
''White Lilies Island'' is the second studio album by Australian singer Natalie Imbruglia released by RCA Records in the United Kingdom on 5 November 2001. The name of this album comes from the location of Imbruglia's home in Windsor, on a peni ...
'' by
Natalie Imbruglia
Natalie Jane Imbruglia ( , ; born 4 February 1975) is an Australian singer and actress. In the early 1990s, she played Beth Brennan in the Australian soap opera ''Neighbours''. Three years after leaving the programme, she began a singing caree ...
, which used the Cactus Data Shield and was released in November 2001. With only a minor mention of the CDS in the small print of the CD case, the album was the subject of many complaints from consumers who found that they could not play the CD on non-Windows computers, games consoles and some other devices. Cases included the
Xbox
Xbox is a video gaming brand created and owned by Microsoft. The brand consists of five video game consoles, as well as applications (games), streaming services, an online service by the name of Xbox network, and the development arm by the ...
repeatedly playing only a small portion of
track 1, while
PlayStation 2 users could play
track 2 but not track 1.
BMG later provided uncorrupted copies of these CDs to consumers. Only the initial European release was copy-protected.
Controversy
Macrovision made a number of controversial claims about the software which were subsequently proven false:
At the same time, widely circulated reports that the Macrovision software behaved in ways indistinguishable from a
computer virus were also found to be false, as was the notion that the software provided any substantial copy-protection.
Macrovision CDS software existed principally in two versions: "CDS-200" and the subsequent "CDS-300."
Versions
The first versions of the system were CDS-100 and CDS-200. Later, a CDS-300 system that features an active software protection was introduced.
See also
*
Copy Control
References
{{Reflist
External links
Macrovision Website
Compact Disc and DVD copy protection