Subject: RE: [eap] Re: Eap keying review: use of MSK/ EMSK for AMSK creation

From: "Nakhjiri Madjid-MNAKHJI1" <[email-masked]>
Date: Tue, 8 Nov 2005 16:57:29 -0500

I think at least for handover or for MIP type applications we can work
with this comfortably, i.e. have an HO-AMSK and a PMIP-AMSK and so on.
And for HO, I will derive all the keys that are needed for HO-AMSK.

However, as we discussed during HOKEY meeting last night, this makes the
assumption that the AAA nows at the time authentication, about all the
applications for which it needs AMSKs for. This works for now, since we
can say that a well designed system should make all AAA decisions
(especially authorization ones) at once. Still it would be nice if do
not add the limitation that prevents the AAA layer/ server to later ask
for another keys, to be exact, if we do not require deletion of EMSK
immediately after AMSK creation. I cannot come of a specific example
right now.

Madjid

>So this prohibits the AAA server to take EMSK and create new keys
>  
>
We may have discussed this already, but this is I believe correct. The
EMSK should not be handed to the lower layer. But see below:

>(AMSKs) for new applications or services.  This means the EAP layer 
>must itself authorize each service application and calculate any AMSK 
>that are needed for that application. Not only we are including a role 
>of authorization into an EAP server, but also we are saying the EAP 
>layer must anticipate all applications that need to derive their keys 
>based on the EAP keying process. Should not be the AAA server to make
>  
>
I think we can easily arrange things so that the AAA layer asks for
AMSKs 1, 2, and 3, which fulfils security requirements (EMSK is not
exposed) and does not require application knowledge from EAP layer. Does
this work for you?

--Jari

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From: Yoshihiro Ohba <[email-masked]>
Date: Tue, 8 Nov 2005 17:42:23 -0500

On Tue, Nov 08, 2005 at 04:57:29PM -0500, Nakhjiri Madjid-MNAKHJI1 wrote:
> applications for which it needs AMSKs for. 

I think this assumption has a limitation for MIPv6 bootstrapping.  In
some case, the AAA server may not know which HA is to be chosen by the
MN until an explicit request comes from HA x chosen by the MN.  In
this case, a key for HA x should be generated on-demand basis (but I
am not sure whether use of AMSK or MSK is appropriate for this case).

Yoshihiro Ohba

> This works for now, since we