eap Mailing List: Re: About use of EMSK

[Jari Arkko (jari.arkko]

Rafa Marin Lopez wrote:

> > [Joe] The EMSK MUST NOT be exported to the lower layer.   
> Clarified this point. In your answer you specify "only" lower layer. 
> Did you forget to include AAA layer ? Or do you think AAA layer might 
> receive EMSK?.

Ignoring the definition problems with layers for a while.
I think we know the external behaviour we want. We
want

- Avoid L2 design, implementation, or node compromise problems
 causing the compromise of other L2 networks. Or compromise
 of one application of EAP keys leading to the compromise of
 others.

- Allow crypto-agility for the function used in the key
 derivation.

- Allow different keys to be used for different attachments,
 without keys 2, 3, ... to be based on key 1, which is what
 we would have to do with MSK

- Make it possible to use existing EAP methods.

One way of approaching this is to have the EAP server/AAA server
keep the EMSK, and provide AMSKs for various purposes. Another
is giving the EMSK to the lower layer, but dictating something about
its use.

--Jari