eap Mailing List: RE: Strawman -10/EMSK deletion requirement?

[Salowey, Joe (jsalowey]

The EMSK is the root of all AMSKs, so a compromise of the EMSK
compromises all AMSKs.  Therefore I would like to see the EMSK protected
as much as possible.  Once the EMSK is securely deleted it cannot be
compromised. I would like to see applications be as independent from one
another as possible and not have one application require the EMSK be
cached once its AMSK is generated. This implies a deeper key hierarchy
than if an application derives all of its keys directly from the EMSK.  

Caching itself is new functionality in the system, but seems to be
required whether you cache AMSK or EMSK.  I don't really have a problem
with caching the EMSK if it is required at the system level because all
applications are not known at the right time.  It think it may be OK for
an implementation to cache the EMSK for its own optimizations, but I
would prefer that the caching of the EMSK not be required for any
particular AMSK usage.  Since an AMSK is exportable you have more
options on where it can be cached.  

Hope this helps,

Joe

> -----Original Message-----
> From: Narayanan, Vidya [mailto:vidyan [at] qualcomm.com] 
> Sent: Tuesday, March 07, 2006 12:40 PM
> To: Salowey, Joe; Avi Lior; Jari Arkko
> Cc: eap [at] frascone.com
> Subject: RE: [eap] Strawman -10/EMSK deletion requirement?
> 
> Joe, 
> I can see the problem with transporting the EMSK to other entities -
> however, what really is the concern with caching the EMSK as 
> long as it
> is never exported? Is it just the concern of having to 
> maintain state or
> is there a security concern here? 
> 
> Vidya 
> 
> > -----Original Message-----
> > From: Salowey, Joe [mailto:jsalowey [at] cisco.com] 
> > Sent: Monday, March 06, 2006 2:04 PM
> > To: Avi Lior; Jari Arkko
> > Cc: eap [at] frascone.com
> > Subject: RE: [eap] Strawman -10/EMSK deletion requirement?
> > 
> > Hi Avi,  
> > 
> > > 
> > > Perhaps you missed my poorly stated point :-)
> > > 
> > > What if the user is requesting access to a new application? 
> > > which could
> > > also involve the modification of the user's profile. 
> > > If EMSK is not there, then what do I do? Restart the session? No.
> > > 
> > > At anyrate I belive that there could be other use cases... 
> > I gave two 
> > > reason why:
> > > 
> > > Just-in-time;
> > > Dynamic-Application provisioning.
> > 
> > [Joe] Would you agree with the following:
> > 
> > "For any specific application once the AMSK is generated for 
> > that application there is no requirement to cache the EMSK 
> > for that application, however there may be a need to cache 
> > the EMSK if the system requires other Masks to be generated. "  
> > 
> > This makes the caching more of a system issue than an issue for one
> > particular application.   
> > 
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