eap Mailing List: RE: EMSK Transport Text

[Nakhjiri Madjid-MNAKHJI1 (Madjid.Nakhjiri]

While I have no issue with the first paragraph, I don't understand the
composition of the subparagraph. Sure it is understandable to prohibit
EMSK distribution to third parties, but why are we prohibiting its use
within the parties who derived it?
Don't we think saying EMSK is future use and then say EMSK is not to be
used for this or that is a bit contradictory? 
Either its future use is undefined and is to be defined by other docs or
we have some idea about its future use. Why are going to length
prohibiting the most probable use case of the EMSK while leaving the
rest of use cases open??


-----Original Message-----
From: Narayanan, Vidya [mailto:vidyan [at] qualcomm.com] 
Sent: Thursday, April 06, 2006 3:09 AM
To: eap [at] frascone.com
Subject: [eap] EMSK Transport Text


Section 2 in draft-ietf-eap-keying-11 says: 

"   The EMSK MUST NOT be provided to an entity outside the EAP server or
   peer,  nor is it permitted to pass any quantity to an entity outside
   the EAP server or peer from which the EMSK could be computed without
   breaking some cryptographic assumption, such as inverting a one-way
   function.  The EMSK MUST NOT be transported by the AAA layer.  As
   noted in [RFC3748] Section 7.10:

      The EMSK is reserved for future use and MUST remain on the EAP
      peer and EAP server where it is derived; it MUST NOT be
      transported to, or shared with, additional parties, or used to
      derive any other keys."