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

[Salowey, Joe (jsalowey]

I would add that the AMSK for a particular application should be derived
such that once the AMSK is derived for that application there is no need
to continue to use the EMSK for derivation of additional keys for that
application.  

> -----Original Message-----
> From: Avi Lior [mailto:avi [at] bridgewatersystems.com] 
> Sent: Wednesday, March 08, 2006 10:24 AM
> To: Salowey, Joe; Narayanan, Vidya; Jari Arkko
> Cc: eap [at] frascone.com
> Subject: RE: [eap] Strawman -10/EMSK deletion requirement?
> 
> So there might be reason for caching the EMSKs.  So language like the
> following:
> 
> EMSK is used strictly for generating AMSKs.
> 
> EMSK is not transported out of the EAP Authentication Server Layer.
> 
> EMSK MUST be deleted when the session for which it was created is
> deleted.
> 
> EMSK SHOULD be deleted sooner, when it is no longer required.  
> 
> > -----Original Message-----
> > From: Salowey, Joe [mailto:jsalowey [at] cisco.com] 
> > Sent: Wednesday, March 08, 2006 1:23 PM
> > To: Narayanan, Vidya; Avi Lior; Jari Arkko
> > Cc: eap [at] frascone.com
> > Subject: RE: [eap] Strawman -10/EMSK deletion requirement?
> > 
> > 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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