Information Technology Reference
In-Depth Information
the current PMSI once again to the TD. At this time, the TD notifies the other
messages produced before or after by checking the synchronized time based on the
PMSI, which has already been notified by the TD itself.
[Step 5]
the step for the creation and updating for the ACK message of the MS:
The MS creates the acknowledgement message ACK after checking the {call setup
message} and sends it to the TD through the GMSC. The value of PMSI_cur is the
current value of PMSI, but it is a exact calculated value according to the synchronized
time at the moment when the TD notifies it to the GMSC. In case the MS will renew
the updating of PMSI just after receiving a call request from the GMSC, the value of
PMSI_cur included in the ACK is to be used by the previous value of PMSI, that is,
the value introduced by the synchronize time at the moment when the TD notifies it to
the GMSC.
[Step 6]
the
step for the verification of ACK by the TD:
The TD updates the value of PMSI_cur after the encryption using the short term
secret key K from the ACK message, which is encrypted by the MS, in its own table
as the value of PMSI_acked.
If there is a normal call receiving request to the same MS from the external user
after detecting the illegal attempt from the GMSC in
[Step 3]
,
the GMSC will also
start from
[Step 1]
by reinitializing the value of PMSI_provided by null.
4 Analysis of the Proposed Scheme
The results for the comparison between the present method and the proposed method
are shown in talbe 1 whether the location privacy of the MS is protected. As shown
in table 1, the symbol
means that the passive attack is to be protected as the
collusion between the disinterested party and the NP in the method of TP, but the
active attack is not to be protected. Also, it is not perfect to protect for the attack by
Δ
Table 1.
Comparison between the present method and the proposed method whether the
position and location privacy of the MS is provided
TP Method+
Reachability
Manager[6]
Proposed
Method
GSM[7]
TP Method[3]
Using
PMSI
And TD
Position Privacy
Protection Method
Using
TMSI
Using PMSI
and TD
Using PMSI
and TD
The 3rd Party
○
○
○
○
Passive
attack of the NP
×
○
○
○
Location
Privacy
Protection
Active attack
of the NP
×
×
○
Δ
Collusion with
the NP and
3rd Party
×
○
Δ
Δ
