Klarinet Archive - Posting 000840.txt from 2000/01

From: "Benjamin Maas" <benmaas@-----.com>
Subj: RE: [kl] CDR's pt 2
Date: Tue, 25 Jan 2000 19:02:17 -0500

> I can't see how encryption will prevent copying. I would expect it to be
> easy to write a program to make a bit by bit copy of any cd including the
> encryption code on a PC based CD writer. It would not matter that the
> original CD could not be played through the sound card, but only on
> proprietary equipment - the copy would have the same property, at least
> until someone works out how to get round the encryption.

If you read my post a little more carefully, you would have understood.
Encryption/copy protection does NOT prevent copying by professionals.
Professional (Expensive) gear generally does not pay attention to copy
protection. Consumer equipment does. It will generally not stop somebody
that really wants to make a copy, but will prevent the casual user from
"bending" the rules.

CDs are not encrypted. There is one bit thrown in the stream that tells you
if you can make a digital copy. It is a flag that tells the recording
player if free copies can be made, or if one or none can be made off of that
digital master. It is pretty much out of practice by today... In the
beginning it was widely used, but not so much today.

The encryption of DVD-Audio will work much differently. It will be much
stronger to prevent copies being made (even on a computer) and will also
include a digital water-mark encoded in the music. This will not be heard,
but when the audio stream is analyzed, will tell you where it came from (CDs
have an ISRC code today that kind of does that).

The interesting thing about the copy protection schemes on DVD-Video, is
that they work on analog copies. Most DVDs will alternate light to dark
when recorded onto a VHS tape. I do not know how it works, but it does. I
am sure it is easy to defeat if you want to, but I don't really have a need.

--Ben

Benjamin Maas
Freelance Clarinetist and Recording Engineer
Los Angeles, CA
benmaas@-----.com
http://www.fifthcircle.com

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