From: Alex de Joode <usura@replay.com>
Date: Tue, 23 Jul 1996 15:37:10 +0800
To: cypherpunks@toad.com
Subject: Re: Digital Watermarks for copy protection in recent Billboard
Message-ID: <199607222127.XAA22946@basement.replay.com>
MIME-Version: 1.0
Content-Type: text/plain


[..]
: > The system will have to rely on proprietary tech and security through 
: > obscurity.  Even know how watermarks are stored without understanding 
: > the math, one must be able to somehow garble the sound without 
: > distorting it, but which renders the watermark useless.

: Actually, this would be quite easy.  The "watermark" would be a 
: signal that plays inband, but out of our hearing range during the 
: entire CD.  The human ear can only hear in the 20-20,000 (Hz, KHZ?, 
: whatever) range.  It would be trivial to add a digital ID signal at, 
: say 30,000 or 15 or something like that.  This could then be decoded, 
: if need be.  This seems the easiest and most efficient way.  This 
: could also be defeated with a lot of $$ (and/or a LOT of HD space).  
: If the frequecy is known (it can be found out) it can easily be run 
: through recording studio eqipment that can very effectively isolate 
: the frequency and cut it out.  If you have a LOT of HDD space 
: (digital audio at 2 stereo tracks, not sure of the sampling rate or 
: bit resolution, takes about 20MB of HDD space per minute (2 tracks, 
: good sampling and bit rate) ) you could probably find the freq. 

HDD space is -cheap- 2 gig drives sell voor 350 usd in Holland,
most music cd's contain 70 minutes of recording thus -at your 
20 Mb per minute rate- would require 1.4 gigs. 

So basicly 'CD-pirates' need to buy a PC with a 2 gig HDD and
a CD-R, a 'one-off' investment of say 5000 usd; besides their
normal cd maunfacturing, packaging and transportation, those
additional 5000 usd are peanuts compared to the total investment
for pirating CD's.

: fairly easily by isolation and just edit it out, and write the new 
: stuff to a CD-R.  If the signal is purely digital, I would imagine 
: that it might be even easier that if it were an analog signal (?).  
: Someone w/ good equipment (Digital Labs' stuff, or SAW (Software 
: Audio Workshop) would be able to do this w/o much problem.  The 
: question is is the price/effort worth it?  In quantity maybe.  On an 
: individual basis, only if you already happen to have the erquipment.

: I have a suspiscion that this type of thing will not really come to 
: any kind of fruition due to not only the ability to defeat this, but 
: mainly due to things like buying at a garage sale, etc.  If it did, 
: only MASS market piraters would be investigated.  (Another example of 
: a law creating it's own violators.  Don't make the law, there won't 
: be mass piratingof "clean CDs"


bEST Regards,
--

	-AJ-