eap Mailing List: Re: Proposed Resolution to Issue 314: AAA-Key Confusion

[Yoshihiro Ohba (yohba]

On Sun, Jan 08, 2006 at 10:31:05AM -0800, Bernard Aboba wrote:
> The text of Issue 314 is available here:
> http://www.drizzle.com/~aboba/EAP/eapissues3.html#Issue%20314
> 
> The Proposed Resolution is as follows:
> 
> In Section 1.2, change:
> 
> "AAA-Key
>     A key derived by the peer and EAP server, used by the peer and
>     authenticator in the derivation of Transient Session Keys (TSKs).
>     Where a backend authentication server is present, the AAA-Key is
>     transported from the backend authentication server to the
>     authenticator.  In existing usage, the AAA-Key is always derived
>     from the MSK and so can be referred to using the MSK name.  AAA-Key
>     = MSK(0,63)."
> 
> To:
> 
> "AAA-Key
> The term "AAA-Key" is synonymous with MSK."

This does not work for draft-ohba-eap-aaakey-binding-01 where 
AAA-Key = KDF(MSK, AAA-Key-name|key-binding-blob).

Yoshihiro Ohba

> 
> In Section 2.1, change:
> 
> "  An additional step (phase 1b) is required in deployments which
>  include a backend authentication server, in order to transport keying
>  material from the backend authentication server to the authenticator.
>  In order to obey the principle of Mode Independence, where a backend
>  server is present AAA Key transport needs to provide the exported EAP
>  keying material and/or derived keys required for derivation of the
>  TSKs.  Since existing TSK derivation techniques depend solely on the
>  MSK, in existing AAA implementations, this is the only keying
>  material replicated in the AAA key transport phase 1b. "
> 
> To:
> 
> " An additional step (phase 1b) is required in deployments which
>  include a backend authentication server, in order to transport keying
>  material from the backend authentication server to the authenticator.
>  In order to obey the principle of Mode Independence, where a backend
>  server is present, all keying material which us required by the lower 
> layer needs to
>  be transported from the EAP server to the authenticator.
>  Since existing TSK derivation techniques depend solely on the
>  MSK, in existing implementations, this is the only keying
>  material replicated in the AAA key transport phase 1b. "
> 
> 
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