Subject: DH groups for PKINIT

From: Jeffrey Hutzelman <[email-masked]>
Date: Fri, 28 Jan 2005 20:13:41 -0500

This is ticket #530.

In San Diego we agreed to say "MUST group 2, SHOULD group 14".
Larry argues that we need to also say "SHOULD group 16".
He also proposes adding "MAY group 4" (this is an EC2N group).

Are there any objections to these proposals?
Does anyone want to speak up in support of them?

The error code KDC_ERR_KEY_SIZE is used for negotiating DH groups; it is 
returned when the parameters proposed by the client do not meed the KDC's 
requirements.  The e-data for this error is a TYPED-DATA with type 
TD-DH-PARAMETERS, containing a proposal from the KDC.

Larry proposes to change the data for TD-DH-PARAMETERS from a single 
DomainParameters object to a SEQUENCE OF DomainParameters, allowing the KDC 
to propose multiple groups in order of preference.

Are there any objections to this proposal?
Does anyone want to speak up in support of it?

Larry is planning on submitting pkinit-23 with all three of these changes, 
with the expectation that they will be fairly non-controversial.  However, 
we need a consensus for or against each of these before we can send this to 
the IESG.

-- Jeff

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From: Sam Hartman <[email-masked]>
Date: Sun, 30 Jan 2005 21:32:22 -0500

I'll speak up in support of the two shoulds.

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From: Nicolas Williams <[email-masked]>
Date: Mon, 31 Jan 2005 10:40:34 -0600

> Are there any objections to these proposals?

I don't think we need "MAY use group X" -- just don't forbid the use of
any groups not listed.

> Does anyone want to speak up in support of it?

Fine with me, er, except, if we're to allow for the use of ECDH then
instead of DomainParameters we need a CHOICE of DomainParameters and
ECParameters.  For simplicity, if we're to have a CHOICE at all, why not
also have an group number integer -- shorthand for the group's actual
parameters?

So:

   IMPORTS DomainParameters, ECParameters
      FROM PKIX1Algorithms88 { iso(1) identified-organization(3) dod(6)
	 internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
	 id-mod-pkix1-algorithms(17) }

   ...

   TD-DH-PARAMETERS ::= CHOICE {
      dh-params		DomainParameters,
      ecdh-params	[1] ECParameters,
      group		[2] INTEGER (0..65536),
      ...
   }

Nico
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