Subject: [Mipshop] rfc4068bis - MAC Mobility Option for FBU/FBAck protection

From: "Narayanan, Vidya" <[email-masked]>
Date: Fri, 16 Jun 2006 11:03:37 -0700

Hi folks,
After some offline discussion among Rajeev, James and myself, we have
come up with the following option that would allow integrity protection
of FMIP signaling - particularly, the FBU and FBAck messages. The goal
is to have an option format that is common, regardless of the handover
key exchange mechanism used to generate the handover key itself. 

We are seeking WG input on this option - please respond with your
comments. 

Thanks,
Vidya

The description of the option is as follows. 

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                      |  HKE  |  AT   |    Reserved   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           SPI                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|                         AUTH Data             ....
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

MH Option Type = "MAC Mobility Option"

MH Option Length = Length of the MH data field

MH Data Fields: 

HKE (4 bits) = Handover Key Exchange Type ('1' - SEND-based; '2' -
AAA-based;)

AT (4 bits) = Algorithm Type - Defined values - '1' - HMAC-SHA-1
(default); '2' - HMAC-SHA-256

Reserved (8 bits) = Set to 0

SPI (32 bits) = The SPI is used by the MN and the AR to identify the key
when a AAA-based HKE (value '2') is used. In this case, the MN will use
the SPI and AR IP address to locate the key, while the AR can use the
SPI alone to identify the key (the SPI is unique per AR). When a key
resulting from a SEND-based HKE (value '1') is used, the key will be
identified by the CoA and the SPI MUST be set to zero. Therefore, an SPI
value of zero is reserved and MUST NOT be used when a AAA-based HKE is
used. (IANA considerations must request IANA to reserve the value of
zero for SPI). 

AUTH Data = prf(K, MH Data)

Where, prf is identified by the AT field; 

K = HK (Handover Key);  

MH Data is the content of the Mobility Header up to and including the
Reserved field of this option

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From: Vijay Devarapalli <[email-masked]>
Date: Fri, 16 Jun 2006 11:26:52 -0700

why can't you use the Mobility Message Authentication option
from RFC 4285.

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        |  Option Type  | Option Length |  Subtype      |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                  Mobility SPI                                 |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                  Authentication Data ....
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

these two fields are not shown in the figure.

> (default); '2' - HMAC-SHA-256

wouldnt the SPI (and the IP addresses) tell you which key and
which authentication algorithm to use? does it matter if the
key was derived using SEND or AAA network access? for
processing the option, you only need to know which key, right?
maybe I am missing something.

Vijay