Re: [P2PSIP] Including Identity in signature.

[Eric Rescorla <ekr at networkresonance.com>]

At Thu, 24 Jul 2008 17:09:17 -0400,
Bruce Lowekamp wrote:
> 
> Cullen Jennings wrote:
> > 
> > This issues is brought up in section 7.1 
> > _______________________________________________
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> > P2PSIP at ietf.org
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> > 
> 
> For those who haven't looked, the question is whether we need to include 
> the signer's identity in the data signature input.  The draft currently 
> does not.  I'm not aware of any reason to do so (assuming reasonble 
> numbers of bits being used for the keys).

So, the usual rationale here is to prevent substitution attacks.
For instance, an attacker gets a certificate with your public
key but his name and then takes a message you signed and rebadges
it as a message he wrote. It's not clear that this is useful in any
practical setting, but since it's not expensive to prevent, I was sort of
thinking it was worth doing.

-Ekr

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