Subject: RE: [Ipsec] Comments of draft-eronen-ipsec-ikev2-clarifications-02.txt

From: [email-masked]
Date: Thu, 14 Apr 2005 14:33:42 +0300

Tero Kivinen writes:
> 
> Tero Kivinen writes:
> > Also if we think more about the IKE SA rekeying, I do not 
> > think there is any reason to do that unless you also do new 
> > Diffie-Hellman there too. Rekeying IKE SA because of the IKE 
> > message ID wrapping is not common. The current IKEv2 text is 
> > not clear wheather the intension was that IKE SA rekey MUST 
> > have KE payloads, but I think we should mandate them, i.e. 
> > say in the NEW-1.3.2 that KE payloads are not optional
> > there.
> 
> Actually it is clear from the draft-ietf-ipsec-ikev2-17.txt that
> Diffie-Hellman parameter is NOT optional when rekeying IKE. The 
> 3.3.3 lists D-H as mandatory type if the protocol is IKE, and 
> the 3.3.2 does the same in the Transform Type Values table. So 
> KE payloads are not optional in the NEW-1.3.2.

I agree that including D-H transform in IKE proposals is mandatory
(this is clearly said in both 3.3.2 and 3.3.3), but is it allowed 
to have NONE as the value? If it is, including KE payload is not
really mandatory...

Section 2.18 says that SKEYSEED for the new IKE_SA is calculated
as follows:

   SKEYSEED = prf(SK_d (old), [g^ir (new)] | Ni | Nr)

The square brackets in "[g^ir (new)]" seem to imply that NONE
would be allowed... but I do agree with you that it's not 
very useful.

Best regards,
Pasi

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---

From: Paul Hoffman <[email-masked]>
Date: Thu, 14 Apr 2005 11:44:39 -0700

At 2:33 PM +0300 4/14/05, [email-masked] wrote:
>to have NONE as the value?

Yes.

>  If it is, including KE payload is not
>really mandatory...

Disagree: it is mandatory, but it doesn't give you any extra security.

>would be allowed... but I do agree with you that it's not

Agree on both.

Do others agree with this tentative conclusion, that the KE payload 
is required for rekeying IKE SAs, even it is has a value of 0 
(meaning NONE)?

--Paul Hoffman, Director
--VPN Consortium