crypto flaw in secure mail standards

[Ben Laurie]

Enzo Michelangeli wrote:
> 
> ----- Original Message -----
> From: "Greg Broiles" <gbroiles at well.com>
> To: "Enzo Michelangeli" <em at em.no-ip.com>; <cryptography at wasabisystems.com>
> Sent: Monday, June 25, 2001 1:32 AM
> Subject: Re: crypto flaw in secure mail standards
> 
> [...]
> > The digital signature laws I've seen don't mention and don't support the
> > notion of "non-repudiation", which seems to be an obsession among computer
> > security people and a non-issue among legal people. The idea that
> something
> > is "non-repudiable" or unarguable or unavoidable is nonsense. I use it as
> a
> > clue detector - if someone talks about non-repudiation, they don't know
> > much about US contract law.
> 
> I don't know about US contract law, but under Common Law repudiation _is_ an
> issue, and that's why witnessing is required. Moreover, there are attempts
> to change the legal implications of signing a document if this is done in an
> electronic environment, shifting the onus of proof of the claim of forgery
> to the (alleged) signatory. See e.g.
> http://www.firstmonday.dk/issues/issue5_8/mccullagh/#m4 about the
> controversial Article 13 of the UNCITRAL Model Law.

I think you are missing the point - repudiation is an issue, but nothing
is non-repudiable.

It seems pretty fundamental to me - I can deny anything. I might have a
hard time getting away with it, but at the very least you'll have to
demonstrate that my denial is implausible (which is why witnesses help).

It also seems to me that one of the problems with electronic signatures
is that witnessing is harder, at least if you want to be disconnected
from the witness. To make it stick as well as physical witnessing does
would require the witness to actually watch my screen and say "yes, he
definitely intended to sign that document I see on the screen" (note
that I say "intended" because witnesses could also be useful to protect
against fraudulent software). I'd guess that a phone call to discuss the
fingerprint of the document would have some value if presence cannot be
achieved, but it would be hard to deal with fraudulent software by that
mechanism. Reading the whole document over the phone is presumed to not
be an option :-)

Cheers,

Ben.

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

In Boston 'til 1st July.



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