Digital Copy Protection
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[ Digital Copy Protection ]
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I've recently become aware of digital copy protection as an issue with impact on
non-commercial digital recording. It was mentioned several times by attendees (there
wasn't anything on the program) at the CFP98 Conference (reviewed in my last column).
It was also brought to my attention by member Myles Losch. I thought it might be an
issue of interest to SIGGRAPH members. One comment made by a CFP attendee
suggested that Digital Audio Tape (DAT) devices have not been good sellers because the
copy protection mechanisms limit their potential usefulness
Myles provided me with two useful references. The first discusses digital video standards
to control intellectual property on Digital Video/Versatile Disc (DVD's) and IEEE 1394
FireWire broadband links. Please see the DVD FAQ at
www.videodiscovery.com/vdyweb/dvd (this discussion refers to the April 7, 1998 version
which will probably have been revised when you read this). Myles says to note especially
items 1.10 and 1.11, plus 2.10 on Divx triple-DES cryptography and to also note items
1.12 and 3.6 on related audio work.
The second reference is www.hrrc.org, a web site run by the Home Recording Rights
Coalition (HRRC). The HRRC provides information about legislation which addresses copy
protection on recording devices. The HRRC was founded in 1981 at the time of actions
relating to the legality of using a VCR to "time shift" broadcast television programs. It is
frequently updated so I won't refer to specific items.
The advent of digital recording devices such as DAT and DVD has caused the owners of
recorded intellectual property such as motion pictures and music to renew their concerns
about unauthorized copying. Many you may remember the similar issue raised when
analog audio tape recorders and VCRs first became available. Digital recording devices
are an even greater problem for them because of the ability to make perfect copies,
without the loss in quality when making analog copies.
Typically, technical mechanisms are developed in industry standards committees to
prevent copying and then legislation is proposed which would make it a crime to provide
mechanisms to circumvent copying, rather than the actual act of copying. The problem
comes when an authorized copy is to be made (for example, of material whose intellectual
property rights are owned by the person making the copies or copies made under fair use).
If you make copies for a living, then you have an incentive to go through the hoops to
effect the copy protection.
But if you are simply making a copy of your home movies, or results illustrating your
computer graphics research, it might not be so easy. While many rights-owners do not
seek to prevent this type of copying, it is not their first priority.
All of this is complicated by aspects of international treaties. Treaties in effect and
proposed at the World Intellectual Property Organization may be much stricter in their
interpretation of unauthorized copying than we are used to under current US law which
has strong protections for fair use copying.
Note particularly, that some proposed legislation in the US, would prohibit the sale,
manufacturing or use of any device which can be used to defeat copy protection. Current
laws are directed at the actual act of unauthorized copying. The situation is particularly
interesting when software mechanisms are involved because of the current Bernstein
cryptography export case which has been successful making software protected speech
under the First Amendment. Due to the rapidly changing situation, it's really not feasible
to go into the legislative process in any greater detail here. I urge you to look at the
references (particularly the HRRC site) and their links for the latest information.
USACM has been involved in this mostly as it relates to their stands on intellectual
property and implementation of the international intellectual property treaties.
The DVD FAQ site has excellent descriptions of DVD technology in general. Section 1.11
describes four forms of copy protection used by DVD. Any or all of the schemes may be
present on any particular DVD media.
The Analog Copy Protection System by Macrovision adds colorburst signals and pulses in
the vertical blanking signal to prevent copying using composite video and s-video outputs.
The copy generation management system (CGMS) embeds information in outgoing video
signals to prevent making first- and/or second-generation digital copies (as with DAT, but
giving more control to the rights-owner). The content scrambling system (CSS) and
Digital copy protection system CPS) both use encryption to prevent unauthorized copying.
Section 1.10 describes "regional codes" which can be used by content originators to
control which parts of the world a DVD may be played. This means that a DVD
purchased in one country might not be playable in another, a particularly vexing problem
given the potential of international electronic commerce.
Section 2.10 presents a description of Divx proposed by Circuit City. Divx would permit
the purchase of a DVD at a cost just above a one time rental and then play it once
(perhaps with a time limit). Additional plays might require payment of additional fees. To
effect the payment of additional fees and authorizations, a telephone connection to the
player would be required.
Like the legal situation, the technical situation is constantly changing, although not so
rapidly. Still, it's not reasonable to go into greater detail here; again, I urge you to check
the reference for current information.