Subject: [AAA-WG]: RE: [Mip4] dynamic keys

From: "James Jing" <[email-masked]>
Date: Thu, 12 Feb 2004 08:55:07 +1100

Hi Henrik,
 
You are right on DH in that on DH does not provide authentication at
all. However, the tunnel setup using DH can be mutually authenticated in
a separate exchange, like in IPSEC. 
 
Provided that HA posseses a certificate, then one can perform
key-exchange and HA authentication first, and MN authentication later.
For example, MN sends its DH data using the public key of the HA, but
the server sends its DH data in the clear, one can at least authenticate
the HA in the process and the MN can trust the tunnel to later send it
its password (if PAP) or digest.
 
Alternatively, one can employ RSA public key encryption to exchange a
MN-generated session key as the same time as authentication is taking
place (one can exchange the session key first, then exchange MN
authentication). TLS-EAP practically does that. 
 
I personally think it is a good idea to relieve the AAA server of
problematic involvement in the session encryption key, if possible. 
 
James

  _____  

From: Henrik Levkowetz [mailto:[email-masked]] 
Sent: Wednesday, February 11, 2004 8:56 PM
To: James Jing
Cc: Jeremy A. Greene; [email-masked]
Subject: Re: [Mip4] dynamic keys

Hi James, 

Wednesday 11 February 2004, James Jing wrote: 
> Why can't the session key be dynamically negotiated (say using 
> Diffie-Hellman) together with the Mobile-Node to AAAh (via HA etc) 
> mutual authentication messages? 

If you're talking of the initial bootstrapping MN-AAAH key, a
dynamically 
negotiated session key would make it possible to encrypt the session, 
but would provide no assurance that either parties have any particular 
identity - i.e., it gives no Authentication. 

        Henrik 

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