Re: [IETF-PKIX] Key Usage Profile

[Simonetti David <simonetti_david@xxxxxxx>]

Bob,

As you've brought forth the legal implications of claiming non-repudiation
during signature, I'd also recommend checking the integrity of each object that
is signed with non-repudiation.  Hence, I'm going to want (need)
digitalSignature to be a valid key usage as well.

Also, I wouldn't expect to limit the use of a public key certificate based
solely on the key usage bits.  Just because nonRepudiation isn't set in my
certificate doesn't mean that my system does not provide non-repudiation.  It is
possible to deal with such an issue within the certificate policy of the
community (e.g., SET).  I've seen nothing in a PKIX document that restricts me
from doing such.

Finally, the processing of the extensions is still a certificate policy issue.
There will be (and are) communities that require specific extensions, as well as
specific key usages, to appear in a certificate.

Dave Simonetti

Bob Jueneman wrote:

> David,, Steve, Denis, and others,
>
> Just to test my understanding of this, if I have a certificate which
> includes the nonRepudiation key usage, I would be ill-advised to use it to
> sign a email message containing a draft contract if I am not prepared to be
> legally bound by it, or unless I needed to be able to substantiate my good
> faith in negotiations, and the drraft was clearly labelled as such. Correct?
>
> And likewise, if I have a certificate which includes the nonRepudiation bit,
> I would be ill-advised to use that certificate to authenticate an SSL
> session, unless I was prepared to be legally bound by the contents
> transmitted over that session?
>
> On the other hand, if I receive a payment order which only has the
> digitalSignature bit set, and not the NonRepudiation bit, I should assume
> that the information was provided FYI, but I shouldn't bet the ranch on it?
>
> And what do we make of a digital signature which is verified by a
> certificate which has neither of the bits set?
>
> I think the attorneys and business practice people will follow whatever
> course we chart here, but we should be careful what we ask for.  Semantics
> are important!
>
> Bob
>
> Robert R. Jueneman
> Security Architect
> Novell, Inc.
> Network Services Division
> 122 East 1700 South
> Provo, UT 84604
> 801/861-7387
> bjueneman@novell.com
>
> "If you are tring to get to the moon, climbing a tree,
> although a step in the right direction, will not prove
> to be very helpful."
>
> "The most dangerous strategy is to cross the chasm in two leaps."
>
> >>> "Simonetti David" <simonetti_david@bah.com> 11/21 2:22 PM >>>
> All,
>
> For those following the key usage profiling issue, I still can't say
> that I'm convinced that nonRepudiation will be exclusive of
> digitalSignature signature in practice, but I respect the opinions that
> I have received.
>
> I recommend that the key usages be profiled in some manner similar to
> the following:
>
> "CAs shall:
>
> Set digitalSignature when the security services of authentication and
> data integrity are to be applied to the validation of a signed object;
>
> Set nonRepudiation when the security service of non-repudiation is to be
> applied to the signed object;
>
> Set both digitalSignature and nonRepudiation when all of the security
> services of authentication, data integrity, and non-repudiation apply to
> the signed object."
>
> If I hear no objections, I will go forth with this.
>
> Dave S.
>
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