Subject: Re: What non-repudiation is not and the PA bit, was Re: To Be, or NR To Be ...

From: [email-masked]
Date: Wed, 18 Aug 1999 14:00:38 -0400

Does most of the group agree that it is true of the nonRepudiation service
that:

     It is required by the NR service that a digital signature be associated
with the object signed (or an unambiguous reference to it) and with the signer's
certificate (or an unambiguous reference to it) in such a way that an
independent verifier can later verify whether the signature is a valid one for
the indicated object using the certified key.

     If so, then the debate we have been having is about whether that condition
is sufficient to characterize the NR service as well as necessary to do so.
Furthermore, the set of data formats which facilitate meeting this requirement
includes some well-known formats such as CMS SignerInfo and (in the future) XML
Digital Signatures.

          Tom Gindin

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From: Tony Bartoletti <[email-masked]>
Date: Wed, 18 Aug 1999 11:45:17 -0700

>the indicated object using the certified key.

That really depends upon what one means by "can later verify" and by
"valid for the indicated object".

I think "independent verification" is a theme common to most of the
discussion (some may have other views;)

Most folks take "can later verify" to mean that the relevant objects (certs,
CRLs, etc) have been sufficiently archived/timestamped/notarized/whatever
so that later (mechanical) digital signature verifications have meaning.
I assume this would be a component of most NR-thingies.

But "valid for the indicated object" conjures up a zoo of possibilities.
How many "types" of object might require their own unique "valid-for"
conditions?  And is it reasonable to work from the assumption that a
one-shot (cert-bit + CP/CPS) combo will be sufficient to identify that
particular object's "valid-for" conditions, and whether they have indeed
been met?

Might I need a key that says "indicates user awareness of liability",
another that says "may be used as evidence", and another that says
"establishes a non-rebuttable presumption"?  Might I be required to
sign some "legal" objects with multiple keys?  And is the simple
identification of "proper-key-type" sufficient, or must some kind
of "witness signatures" be required, to afford certain transactions?

>includes some well-known formats such as CMS SignerInfo and (in the future) XML

Tony Bartoletti                                             LL
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