eap Mailing List: Re: Issue: AAA-Key should be derived from AMSK

[Florent Bersani (florent.bersani]

Joe,

I believe this is tracked as Issue 266 
(http://www.drizzle.com/~aboba/EAP/eapissues.html#Issue%20266) isn't it?

Thanks for proposing text :-)) I concur.

Florent

Joseph Salowey wrote:

> Description of issue
> Submitter name: Joe Salowey
> Submitter email address: jsalowey [at] cisco.com
> Date first submitted: 10/4/2004
> Reference: 
> Document: Keying Framework
> Comment type: 'T'echnical
> Priority: 'S' Must fix
> Section: 2.2, Appendix C, Appendix E
> Rationale/Explanation of issue:
>
> The AAA-Key should be derived from the EMSK directly,
I assume that you meant *should not*

> it should either be
> derived from the MSK alone or form an AMSK (which is derived from the EMSK).
> This is to limit the exposure of the EMSK outside of the EAP framework and
> to ensure that the EMSK derivation maitnains computational separation of
> keys.  
>
> Requested change:
>
> Section 2.2:
>
> Change 
> "On both the peer and EAP server, the exported MSK and EMSK are
>   utilized in order to calculate the AAA-Key, as described in Appendix
>   E."
> To
>
> "On both the peer and EAP server, the exported MSK and keys derived from the
> EMSK (AMSK) are
>   utilized in order to calculate the AAA-Key, as described in Appendix
>   E."
>
> Figure 3 should be changed to show that the AAA-Key is derived from an AMSK
>
> Appendix C:
>
> Figure C1 should show the AMSK going to the backend server instead of the
> EMSK
>
>
> Appendix E:
>
> The EMSK should not be used directly in AAA-Key derivation. Text follows:
>
> "Where keying material is provided by the backend
>   authentication server, a key hierarchy derived from the EMSK, can be
>   used to provide cryptographically separate keying material for use in
>   fast handoff.  Instead of using the EMSK directly a application specific
>   key is derived, the AMSK, as described in seciton F:
>
>   AAA-Key-A = MSK(0,63)
>   AAA-Key-B = PRF(AMSK(0,63),"EAP AAA-Key derivation for
>               multiple attachments", AAA-Key-A,B-Called-Station-Id,
>               Calling-Station-Id,length)
>
>   AAA-Key-E = PRF(AMSK(0,63),"EAP AAA-Key derivation for
>               multiple attachments",AAA-Key-A,E-Called-Station-Id,
>               Calling-Station-Id, length)"
>
>
>
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