RE: Options, was Re: To Be, or NR To Be ...

["Bob Jueneman" <BJUENEMAN@xxxxxxxxxx>]

Elliot,

A couple of observations.

First, I'm not sure that I agree that if the keyUsage extension is critical, 
and NR==0, that you are forbidden to use "it" (whatever "it" might be).

I know that this issue has been discussed previously in conjunction with another
attribute, and I may not be remembering it properly, but I thought that the 
Critical bit merely meant "if you don't understand what this bit means, 
you should reject the certificate"  That's not quite the same thing as 
saying "if you do understand what this bit means, you are absolutely
compelled to either do or not do that thing, under pain of ...?"

Secondly, although NR==0 clearly means, "you shouldn't assume that
the NR property applies" it isn't clear that that is useful if I don't know what
NR means.  What is the CA, the subscriber, and/or the relying party 
supposed to do in that case?  It still isn't clear, and so it's an empty bag.
Maybe NR means, 'hang your clothes on a hickory limb, and don't
go near the water." :-)  I don't know what that means, either.

I am beginning to be of the opinion that we should deprecate the NR 
bit entirely, and then define several new bits to define exactly what we 
do mean, as I suggest under the "subdividing the NR bit" thread.

I certainly agree that "go read the CPS" adds little or nothing. Does
NR==0 mean that I don't have to read the CPS?  If so, that would be 
a very useful thing to have, but I don't think it means nonrepudiation. :-)

At this point, I am afraid that there is so much baggage, implied semantics,
and past history in the name "nonrepudiation" that I don't think we will 
ever achieve consensus.

There is a little bit of merit in Ed's Proof of Authentication label, but that doesn't
really connote what I would like at least one of the bits to mean.  And 
"rebuttable presumption" also has some merit, and so does "intent to sign".

I think that everyone but Steve Kent believes that the name "nonrepudiation" 
conveys something quite different than the current definition, which to my 
mind at least is hopelessly vague and circular.  However, we have not 
yet achieved consensus on one single definition of what it does mean, 
in part, I think because there are multiple things going on that are all 
interrelated, and a single bit is simply not sufficient to cover them all.

What do others thing about deprecating NR, and starting over with a 
clean sheet of paper?

Bob
>
>
>>>> Elliot Ginsburg <ginsburg@cygnacom.com> 08/25/99 02:08PM >>>
>I think everyone agrees that the keyUsage extension provides more
>information than would be present without it. The discussion on this
>list seems to be, exactly what information does it provide? Anyone have
>a clear proposal to make for what it means, other than 'go read the
>CPS', because this adds nothing.
>
>It seems easy to decide that NR==0 means 'don't use it for NR' (if
>critical, you're forbidden to; if non-critical, you're advised not to).
>But what exactly does NR==1 convey? From reading this list, I might
>conclude it means 'you might want to use it for NR, depending on the
>policy, your requirements, and the availability of NR services to you'.
>While this doesn't do much, at least NR==0  is still very useful.
>
>Elliott N Ginsburg
>CygnaCom Solutions
>ginsburg@cygnacom.com 
>703-848-0883
>703-848-0960(FAX)
>
>> -----Original Message-----
>> From:	David P. Kemp [SMTP:dpkemp@missi.ncsc.mil] 
>> Sent:	Wednesday, August 25, 1999 2:48 PM
>> To:	ietf-pkix@imc.org 
>> Subject:	Re: Options, was Re: To Be, or NR To Be ...
>> 
>> 
>> > From: Tony Bartoletti <azb@llnl.gov> 
>> > 
>> > In some ways, the NR-bit is like marketing bottles of wood alcohol
>> that
>> > are simply labeled "alcohol".  The designation is "not necessary" to
>> those
>> > that have performed investigation and use the liquid for cleaning
>> purposes.
>> > The designation is "not sufficient" for those who assume that the
>> liquid
>> > is grain alcohol and can be taken internally.
>> 
>> 
>> Your position is that more information on the label is better?
>> 
>> What label should be attached to a key which is known to be relatively
>> less suitable for supporting a NR process (perhaps because the binding
>> between a single individual and a specific private key is weak or
>> nonexistent) - "Key, NR=0", or simply "Key" ?
>> 
>> The "necessary and sufficient" line of reasoning is as bogus with
>> respect to the NR bit as it is with respect to any other bit.  A
>> necessary and sufficient statement says that the set of keys (or more
>> generally, the set of technologies) which can support and will provide
>> an XX operation is identical to the set of keys which have the XX bit
>> asserted in a certificate.  No matter what you value you substitute
>> for
>> XX (digitalSignature, nonRepudiation, keyEncipherment, ...
>> decipherOnly), the "necessary and sufficient" condition is patently
>> false.  We have the keyUsage extension because a cert with it provides
>> more information than a cert without it, not because the extension is
>> either necessary or sufficient to achieve any particular security
>> goal.
>
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