Subject: [IPsec] ike sa rekey key generation

From: Scott C Moonen <[email-masked]>
Date: Fri, 26 Jun 2009 15:51:46 -0400

ikev2bis says the following:

   SK_d, SK_ai, SK_ar, SK_ei, and SK_er are computed from SKEYSEED as
   specified in Section 2.14.

Is it correct to assume that SPIi and SPIr as used in this rekey 
calculation are from the new, rekeyed IKE SA?  Is it worth specifying that 
explicitly?  Ni/Nr is more obvious, since those are explicitly exchanged 
with the CREATE_CHILD_SA rekey exchange.  But the rekey exchange has two 
associated SPIs (the old SA's SPIs for the messages themselves, and the 
SPIs within the SA proposals), and it might be helpful to clarify this.

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

---

From: Paul Hoffman <[email-masked]>
Date: Mon, 29 Jun 2009 14:50:17 -0700

At 3:51 PM -0400 6/26/09, Scott C Moonen wrote:
>Is it correct to assume that SPIi and SPIr as used in this rekey calculation are from the new, rekeyed IKE SA?  

Yes. It would not make sense to have the new values be based on the old SPIs.

>Is it worth specifying that explicitly?  Ni/Nr is more obvious, since those are explicitly exchanged with the CREATE_CHILD_SA rekey exchange.  But the rekey exchange has two associated SPIs (the old SA's SPIs for the messages themselves, and the SPIs within the SA proposals), and it might be helpful to clarify this.

I will add this to the next version of the ikev2bis document.

--Paul Hoffman, Director
--VPN Consortium