I realize that this is *slightly* simplistic, but comparing 2 (preferably 3 or more) copies of the data with different watermark contents should quickly reveal where and what constitutes the watermarking. Of course, there are methods to make this more onerous - MACing the watermarked data for one - but nothing a determined counterfeiter couldn't work around. It only takes one, after all. I'm currently working my way through Schneier's 'Secrets and Lies'. He has one comment I like to the effect that trying to make data not be copyable is a task on a par with trying to make water not be wet. Peter Trei
---------- From: Adam Back[SMTP:adam@cypherspace.org] [...]
Of course the whole concept of watermarking is broken at all levels, copying can not be prevented as the content can typically be reencoded and lose the watermark, quality is in heavy contention with the ease with which the watermark can be removed. Even if it is keyed. And ultimately content can plausibly deniably be stolen and all it takes is one copy.
Adam