Subject: [HOKEY] why bother?

From: "Dan Harkins" <[email-masked]>
Date: Mon, 10 Dec 2007 09:31:06 -0800 (PST)

After leaving the HOKEY meeting in Vancouver I came to the realization
that there is strong consensus that it is OK to move keys from one
distributed system of computers (domain A) to another distributed system
of computers (domain N) through a multiplicity of other distributed
systems of computers (domain B, domain C, ...). Most people in the group
seem to think so, Russ is happy to (re)interpret RFC4962 to permit it,
the ADs didn't complain.

  Furthermore, it was asserted that this is still "just like IPsec"
because if any of the players do things they're not supposed to then
all bets are off. So as long as a given distributed system of computers
trusts nother distributed systems of computers and (by transitive trust)
trusts all other distributed systems of computers that are trusted by
these immediately trusted distributed systems of computers then everything
is fine from a security perspective. And we have lawyers to deal with any
rogues in the mix.

  So if this is all fine then why are we going to the trouble of having
this complicated key hierarchy? Well the explanation from the EMSK key
hierarchy draft is, "[in] order to prevent security problems in one usage
from interfering with another usage...." But the justification for this
massive key sharing is that there aren't going to be any security problems.
Furthermore, this key hierarchy isn't preventing security problems from
one usage from interfering with another usage since any entity in any of
those distributed systems of computers (domains A, B, C, ..., N-1) that
comes into contact with a key for domain N can impersonate any entity in
the distributed system of computers that comprises domain N. If there are
"security problems" in any of those domains then this key hierarchy does
not stop them from affecting other domains.

  And what is the need for usage-specific keys since the entities in this
distributed system are all trusted? What's the threat model?

  If the assumption is still that a peer will do a full EAP authentication
every time it visits a new domain then let's do away with this complex
key hierarchy. The peer has a key for this domain and she'll use it for
that domain, for whatever use she feels like. If she goes to another domain
she'll get a brand new key and use it for that domain.

  Dan.

On Mon, November 19, 2007 12:35 pm, Lakshminath Dondeti wrote:
> Hi Charles, Glen,
>
> As one of the authors of the "EMSK Root Key Derivation" draft, I think
> the draft is ready for WGLC.  We have been discussing this topic for a
> long time in the IETF with Joe and Pasi's work in the past and within
> the EAP WG.  Furthermore, the document now records the WG consensus on
> the EMSK, USRK and DSRK derivations and usage.
>
> We may have 1-2 issues that are still contentious, but they are in the
> same ballpark as the other discussions we have had in the past in
> advancing 4962 and currently in advancing the EAP keying framework I-D.
>   Let us have those discussions on this list, perhaps as part of LC
> comment resolution.  It's your call of course to have those discussions
> before or as part of WG LC :).
>
> best,
> Lakshminath
>
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