Subject: Re: Confirming the Nominet position

From: Derek Atkins <[email-masked]>
Date: Fri, 28 May 2004 14:02:35 -0400

[email-masked] writes:

> 	i've been told that digital signatures can be used as
> 	legal evidence in some jurisdictions. if true, it is 
> 	conceivable that by my holding signed data indicates,
> 	if not the path by which i received said data, who signed the
> 	data.  

Except signatures can be removed.  For example, if I were to
(theoretically) illictly obtain a signed document, I could use
the signature to prove to someone that W went to war in Iraq
without proof of WMD.  However I don't have to reproduce that
signature in all cases, I could remove it in my copy, so you
couldn't verify the origin of the document.

Watermarking needs to be performed _IN_ the document, not by a
signature.  And all watermarking techniques have been shown to be
breakable via collusion of multiple recipients of the data.

-derek
-- 
       Derek Atkins                 617-623-3745
       [email-masked]             www.ihtfp.com
       Computer and Internet Security Consultant

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