Subject: FW: Is this non-repudiation or NR, and why?

From: Elliot Ginsburg <[email-masked]>
Date: Fri, 20 Aug 1999 09:50:54 -0400

Lets look at the physical model we're trying to emulate.

When I physically sign a piece of paper, my possible rebuttals are:
	1) I didn't sign it (someone else did)	
	2) I didn't know what I was signing
	3) I was forced to sign
Note that one the possibilities IS NOT that I don't consider my
signature to mean anything. It always means, subject to rebuttal, that I
physically created it; I was there, I knew what I was going, etc.
Very often the thing signed defines the meaning of the signature, as in
"I attest to...", "Approved by...", etc., and that is what my signature
is an agreement to.

Whether or not this signed thing is sufficiently trustworthy is a
different question. We have rules for applying signatures which affect
its "strength": doesn't require a witness, required to be signed in
presence of other parties to agreement, requires notarization, etc.
These are determined by the participants in the transaction. For
example, my mutual fund company requires written requests witnessed by a
bank officer; they will not honor any other form of the request, even
though they will have a signed piece of paper. 

In other words, NR is authentication: my signature means, subject to
rebuttal, that I (and not someone else) agreed to whatever is implied in
that transaction, and the paper with my signature is evidence of that
(whether or not the evidence is sufficient or is accepted, it is
evidence). It is up to the participants in the transaction to make sure
that it will be sufficient evidence if contested.

The DS and NR bits are assertions of policy BY THE CA, of how, within
the scope of its use and according to policy, this cert can be used. A
CA might NOT set NR because the key is escrowed, or shared, or some
other reason, but it still offers data integrity within its scope of use
and according to the policies within that scope. For example, if the key
was escrowed, then it won't assert authentication (NR), but it will
assert data integrity because the handling of the key is trusted enough
for that. Another exampel, we're not careful enough with verifying WHO
in this organization really was registered, but we're sure they were
part of this organization. 

Another possibility for not asserting NR could be that this CA does not
sufficiently back-up/archive certs and CRLs so that it wouldn't be
possible to use it later for NR. 

We really should have a data integrity usage, and a NR/authentication
usage. And it seems to me that, by default, NR implies also data
integrity.

Elliott N Ginsburg
CygnaCom Solutions
[email-masked]
703-848-0883
703-848-0960(FAX)

> -----Original Message-----
> From:	Flanigan, Bill [SMTP:[email-masked]]
> Sent:	Friday, August 20, 1999 8:45 AM
> To:	'David P. Kemp'
> Cc:	[email-masked]
> Subject:	RE: Is this non-repudiation or NR, and why?
> 
> Dave,
> 
> 	Again, how do you define "technical non-repudiation"?  Thanks.
> 
> Bill
> 
> > ----------
> > From: 	David P. Kemp[SMTP:[email-masked]]
> > Reply To: 	David P. Kemp
> > Sent: 	Thursday, August 19, 1999 6:13 PM
> > To: 	[email-masked]
> > Subject: 	Re: Is this non-repudiation or NR, and why?
> > 
> [snip]
> 
> > I would like to see a request from the ABA that we cease and desist
> > using the term "technical non-repudiation" 
> > 
> [snip]

---

From: Tony Bartoletti <[email-masked]>
Date: Fri, 20 Aug 1999 10:49:56 -0700

>"I attest to...", "Approved by...", etc., and that is what my signature

I agree.  There seems to be a use-focus to most of the discussion that
one is signing a "promise", hence NR attests to the validity of the
promise.

In contrast, if I were to send an email to someone containing a threat
to their life, and part of the evidence that points to me was my
digital signature on that email, I don't think the court will be
impressed when I demonstrate that the cert's NR-bit was not set,
so "I didn't intend to be held liable for the content."  That would
be ridiculous, because the "act-in-question" is the signed object
itself, not whether the promise/threat contained therein would,
in the future, be faithfully "executed" (sorry about that!)

___tony___

Tony Bartoletti                                             LL
IOWA Center                                              LL LL
Lawrence Livermore National Laboratory                LL LL LL
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