limits of watermarking (Re: First Steganographic Image in the Wild)

[Roop Mukherjee]

On Wed, 17 Oct 2001, Ben Laurie wrote:

> Adam Back wrote:
> > Another framework is to have players which will only play content with
> > certified copy marks (no need for them to be visible -- they could be
> > encoded in a logo in the corner of the screen).  The copymark is a
> > signed hash of the content and the identity of the purchaser.
> >
> > This could be relatively robust, except that usually there is also a
> > provision for non-certified content -- home movies etc -- and then the
> > copy mark can be removed while still playing by converting the content
> > into the home movie format, which won't and can't be certified.
>
> The other obvious weakness in such a scheme is that the player can be
> modified to ignore the result of the check - rather like defeating
> dongles, which have yet to exhibit any noticable resistance to crackers.
>

The fact that someone can break open his box/software and sucessfully
invalidate their verification scheme does not mean that there is no value in
copy marks. Initial schemes that verify copymarks may not make it
impossible to cheat, but they will raise the barrier. To compare, in
theory one can break even strong encryption. We only try to make it
"sufficiently" hard. The copy protection schemes that are being debated
may not be as good at raising the bar as some others like SSL but the
recording industry will push ahead because evey copyright violator
discouraged means savings in the piracy attributed losses that their
analysts (somewhat mysteriously) produce.

-- Roop
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