limits of watermarking (Re: First Steganographic Image in theWild)

[Ben Laurie]

Roop Mukherjee wrote:
> 
> On Thu, 18 Oct 2001, Marc Branchaud wrote:
> 
> >
> > This analogy doesn't quite hold.
> >
> > Copy protection need only be broken once for the protection to be disabled
> > for a particular piece of work.  Also, once the scheme is known for one piece
> > of work, it is extremely easy to break the scheme for other pieces, and in
> > particular to write an application that will do so.
> >
> > With crypto's bar-raising, OTOH, breaking one instance, like an SSL stream or
> > an AES key, does not break all other uses of SSL or AES.  In particular, SSL
> > & AES will provide the same degree of protection for any other communication
> > of the same data between the same or other parties.  Also, good crypto
> > schemes are already widely known and designed explicitly so that knowledge of
> > the scheme does not break the scheme.
> >
> >               M.
> 
> I am not certain which scheme of copy protection you are refering to. But
> I agree that any scheme that relies on a secret recipie (ala Coca Cola)
> would not be effective. The analogy was intended towards publicy know
> provably strong means of copy protection. Most security measures these
> days would be foolish to choose otherwise. My impression of the DRM
> work that was being undertaken is that most of it aiming towards "open
> specifications" that are provably secure. For instance the SDMI charter
> says, "...to develop open technology specifications that protect the
> playing, storing, and distributing of digital music ...". Measures like
> this would indeed raise the bar in much the same way as some other
> security measures like SSL did.

If it were possible, it would indeed raise the bar. The problem is, it
would seem, that it is not possible to have a provably strong means of
copy protection, publicly known or otherwise. The SDMI charter can say
what it wants, but that doesn't mean it can be achieved. The arguments
that support the impossibility of the goal have been well rehearsed, so
I won't repeat them here.

Cheers,

Ben.

--
http://www.apache-ssl.org/ben.html

"There is no limit to what a man can do or how far he can go if he
doesn't mind who gets the credit." - Robert Woodruff



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