Re: [Mobopts] Key transfer issue for pana-cxtp

Hi james,

On Thu, Mar 31, 2005 at 12:00:14PM -0800, James Kempf wrote:
>
> >
> > Currently we use the mechanism described in pana-mobopts for key

the PANA-Start-Exchange (PSR/PSA) is not protected

> assume PAA-nonce is for nPAA, right? How is that protected (I'm assuming

The PAA_Nonce is created by the PAA and sent to the PaC the PaC_Nonce is created by the PaC and sent to the PAA

> > Thus an attacker can get AAA-Key-new if:

my notation is misleading. I'm sorry about that. What I meant is that to get the AAA-Key the attacker must compromise the pPAA. In fact we can replace "=>" by "The attacker must"

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> What's to prevent an attacker from starting a PANA exchange

exactly.

>
> > => others ?
> > * it knows Nonces
> > => sniff MN-nPAA PANA-Start-Exchange
> >
> > We need to know if this key transfer is ok from a security point of
> > view.

I got it, The criteria of interest is:

"Compromise of a single NAS cannot compromise any other part of the system, including session keys and long-term keys"

In our situtation, the compromision of the pPAA (NAS) can compromise other part of the system. But the attacker must perform other operations:

• sniff MN-pPAA link to get session-id
• get nPAA's identity
• sniff MN-nPAA link to get Nonces

So this is not only a compromision of the NAS which permit to compromise other part of the system. That's why I'm a little bit confused.

I'd like to get a sort of consensus on this to know if is useful to continue with this idea (transfer of the AAA-Key-int).

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regards,  

-- 
julien.bournelle at int-evry.fr

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