Subject: [HOKEY] MSK vs EMSK

From: Charles Clancy <[email-masked]>
Date: Wed, 24 Jan 2007 19:31:22 -0500

During the interim meeting, there was consensus in the group to use the
EMSK as the root of the reauthentication hierarchy.

There were several reasons for this:

- The key scope for the MSK allows distribution to authenticators, and
if the MSK were used as the base of a keying hierarchy, its use would
have to be rescoped to be variable on a session-by-session basis (in
order to support both HOKEY and legacy EAP peers).

- Proper scoping of the MSK on a per-session basis requires the
definition of some sort of signaling between the EAP peer and a reauth
server.  As one is talking EAP and one is talking AAA, direct
communication between the two is difficult, especially since there is no
network access yet.

- Currently the MSK must be exported to the "EAP lower layer", and if
it's going to be exported to HOKEY rather than a lower layer, we need to
convince ourselves that HOKEY really is a lower layer, when in fact it's
part of EAP.  Updating the semantics could require updates to a number
of RFCs including 3748.

- The key scope of the EMSK requires it stay at the EAP server, which
provides proper scope for HOKEY reauth purposes.

- The proposed changes to the EMSK/USRK hierarchy would make it very
suitable for reauth in a visited domain.

The only reason to use the MSK was that we wouldn't need to fix
non-compliant EAP implementations to support generation of the EMSK.
The group didn't feel this was sufficient justification to use the MSK.

-- 
t. charles clancy, ph.d.  <>  [email-masked]  <>  www.cs.umd.edu/~clancy

_______________________________________________
HOKEY mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/hokey