Subject: Re: [mobile-ip] Authentication Data as a BU suboption

From: Lars Henrik Petander <[email-masked]>
Date: Wed, 1 Aug 2001 20:24:17 +0300 (EET DST)

Hi Vijay,

I am mostly neutral on whether the authentication data should be in the AH
or in the BU itself. Both solutions have their benefits and drawbacks.  
However, the version 14 of the draft should be clearer on how the BSA is
created, used and destroyed:

The BSAs should be deleted when MN deregisters, since the replay state for
MN is deleted then. If MN and HA have a preconfigured shared secret they
need some new mechanism of deriving session keys to use for authenticating
BUs and BAs. (If the same key is used for multiple sessions the replay
protection from sequence numbers is broken) 

Henrik
 
On Tue, 31 Jul 2001, Vijay Devarapalli wrote:

> hi,
> 
> I like authentication data as a BU suboption. this 
> authentication data protects the BU option and the 
> home address option alone. nothing else. draft-14 
> gives a cleaner solution for authenticating BU's IMO.

---

From: "Charles E. Perkins" <[email-masked]>
Date: Wed, 01 Aug 2001 13:52:23 -0700

Hello Henrik,

> MN is deleted then.

It is likely that the existing mechanism for replay protection could be
improved.  For instance, we could specify an explicit field in the
Binding Update option data for this purpose, and maybe that should be
done in preference to relying merely on the Sequence Number field.
Alternatively, we could continue to go with the Sequence Number field
and just accept the possibility for more frequent rekeying.  However,
I get the sense that people will desire that rekeying be done every
few days or weeks anyway, so maybe it's O.K. as is, even between
mobile node and home agent.

This means that a BSA could be retained as long as the sequence
number could still protect against replays (i.e., the replay state
would become part of the BSA and not be deleted).

>                    If MN and HA have a preconfigured shared secret they

Agreed, and this has been noted within the specification.  It is an
open question how adequate or inadequate the current proposed use of
the sequence number might be.  I am, myself, completely neutral on
the issue, as with most of the current security issues.

Regards,
Charlie P.