Subject: Re: [IPsec] #121: Rekeying IKE SAs: KEr errors and PRF question

From: Paul Hoffman <[email-masked]>
Date: Thu, 10 Dec 2009 11:41:01 -0800

At 9:34 AM -0500 11/24/09, Scott C Moonen wrote:
>
> > > Section 2.18 also states that in the case of the old and new IKE SA
>> > selecting different PRFs, that the rekeying exchange (for SKEYSEED)
>...snip...
> > new PRF, is when new IKE SA is used to generate KEYMAT, or SKEYSEED
>> for next IKE SA rekey. But I agree this is not very clear, and could
>> be clarified.
>
>We've interpreted it as follows: 1) the old IKE SA's PRF is used to produce SKEYSEED, but 2) the new IKE SA's PRF is used to produce SK_x.
>
>We've successfully interoperated with a number of other platforms that seem to have made the same interpretation.

At 4:50 PM +0200 11/24/09, Tero Kivinen wrote:
>Scott C Moonen writes:
> > We've interpreted it as follows: 1) the old IKE SA's PRF is used to
>> produce SKEYSEED, but 2) the new IKE SA's PRF is used to produce SK_x.
>
>Hmm... when reading my code, it seems I do the same, but when I read
>the text I interpreted it differently, so I think we need some
>clarification text there...

Can either of you propose the new text?

--Paul Hoffman, Director
--VPN Consortium

---

From: Scott C Moonen <[email-masked]>
Date: Thu, 10 Dec 2009 14:58:35 -0500

> Can either of you propose the new text?

Here's a first shot.  I think we can move the paragraph later on (starting 
with "SK_d, ...") adjacent to this paragraph to produce:

   The old and new IKE SA may have selected a different PRF.  Because
   the rekeying exchange belongs to the old IKE SA, it is the old IKE
   SA's PRF that is used to generate SKEYSEED.

   SK_d, SK_ai, SK_ar, SK_ei, and SK_er are computed from SKEYSEED as
   specified in Section 2.14, using SPIi, SPIr, Ni, and Nr from the new
   exchange, and using the new IKE SA's PRF.

Scott Moonen ([email-masked])
z/OS Communications Server TCP/IP Development
http://www.linkedin.com/in/smoonen

From:
Paul Hoffman <[email-masked]>
To:
Scott C Moonen/Raleigh/IBM@IBMUS, Tero Kivinen <[email-masked]>
Cc:
IPsecme WG <[email-masked]>
Date:
12/10/2009 02:41 PM
Subject:
Re: [IPsec] #121: Rekeying IKE SAs: KEr errors and PRF question

>
>We've successfully interoperated with a number of other platforms that 
seem to have made the same interpretation.

--Paul Hoffman, Director
--VPN Consortium

---

From: Tero Kivinen <[email-masked]>
Date: Fri, 11 Dec 2009 15:35:49 +0200

>    exchange, and using the new IKE SA's PRF.

That looks good. 
-- 
[email-masked]