Handover mechanisms in next generation heterogeneous wireless ...

PROXY BASED AUTHENTICATION LOCALISATION SCHEME FOR HANDOVER
the local authentication key LAK shared between the MH and the FAP. The AN acts
just as a pass-through, and can not view or modify the two passed nonces. After
receiving the key renew request, the AN forwards it with the encrypted E LAK ( N m '||
N s )
to the FAP. E LAK ( N m '||
N s ) is decrypted at the FAP later using the cached LAK. The
FAP verifies whether N s provided by the MH is the same as what has been included in
the original FAT. If the MH could pass this request origination check, the FAP
generates a new proxy nonce N p ' , and computes the new PMK (PMK’) as follows:
PMK ' � prf ( LAK , PMK || N m '||
N p ' )
(Equation 6.7)
The new PMK’ along with the encrypted proxy nonce E ')
will be delivered to the
- 126 -
( p
LAK N
AN through the FAP-sAN connection (protected by K pa as shown in Figure 6.6). The
AN keeps the PMK’ for renewing the related session key, and forwards LAK ( p ')
N E to
the MH. With the decryption, the MH obtains the new proxy nonce N p ' from
E LAK ( N p ')
, and can derive the new pairwise master key PMK’ according to Equation
6.7.
E
LAK
( Nm
'||
Ns
)
ELAK
( N p ')
EK pa
{ ELAK
( Nm
'||
N s )}
E LAK p
K pa
{ E ( N '),
PMK '}
Figure 6.6 Session key renewal procedure initiated by MH
The sAN can start the session key renewal procedure. This is started by sending a Key
Renew Request to the FAP. Then, the FAP generates the new proxy nonce N p ' , and
sends this nonce N p ' along with the received original mobile nonce N m to the MH for
verification by the MH. The N p ' and N m are encrypted using the LAK so that they can