IEEE C802.16m-09/0126
Project
IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/16>
Title
GAK and GTEK Update
Date
Submitted
2009-01-05
Source(s)
Allan Xu， Lei Jin
Huawei
Re:
IEEE 802.16m-08/052: Call for Comments on Project 802.16m System Description Document
(SDD):
Voice:
E-mail:
zhier81@huawei.com
*<http://standards.ieee.org/faqs/affiliationFAQ.html>
Section: 10.6 Security
Abstract
In 16m we need efficiently mechanism to update GAK and GTEK. This proposal will supply
sufficient procedure to update MBS related key. .
Purpose
Discussion and adopt
Notice
Release
Patent
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GAK and GTEK Update
Allan Xu, Lei Jin
Huawei
1. Introduction
In now 16m , GAK (Group Authorization Key) and GTEK (Group Transmission Encryption Key) are for MBS.
GAK is randomly generated at the ABS. The GTEK is generated locally by using the GAK, the NONCE, the
KEY_COUNT and other identity parameters. The GTEK is used to encrypt data packets of the multicast service
or the MBS and it is shared among all SSs those belong to same multicast/MBS group.
New GTEK shall be derived in the following situations:
• AMS enters to multicast group (derived only in AMS side)
• Generation and transmission of new GAK
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IEEE C802.16m-09/0126
• Group key update procedure for multicast connection.
At the same time considering power saving, we shall support MS can receive MBS when it is in idle state.
How can MS update GAK or GTEK when it is in idle state? We shall support MS in idle state can update its
key efficiently with least power consumption.
2. Solution
In this section we propose GAK update mechanism and GTEK update mechanism respectively.
2.1 GAK update
When GAK updates, BS can use special paging message (MOB_PAG-ADV message in 16e) to indicated
the paging intention is for GAK update, then MS can request updated GAK in RNG-REQ message when it do
ranging procedure, and BS can unicast updated GAK material to MS in RNG-RSP. In this mechanism, MS
doesn’t do whole network re-entry for updated GAK material. In RNG-REQ/RSP interaction MS can obtain
updated GAK, this is more efficient than that MS do whole network entry for updated GAK. And at the same
time overhead decreases because other interactions are omitted.
So we propose that when MS is in idle and GAK updates, BS pages MS with multicast CID or station ID
and one action code to indicate which GAK is updated. If MS receives this paging message it can do ranging
procedure, in ranging procedure MS requests updated GAK in RNG-REQ, and BS includes the updated GAK in
RNG-RSP.
2.2 GTEK update
When GTEK updates, BS can include the updated GTEK in the MBS allocation message (MBS_MAP in
16e), then MS can obtain updated GTEK when it receives MBS Data. As an optional way BS also can include
the updated GTEK in MBS data, in this way MS can obtain updated GTEK when it parse MBS data. In previous
two mechanisms we can see that BS broadcasts the updated GTEK only time, and MS can obtain updated
GTEK when it receives MBS data. These mechanisms can save overhead and MS power consumption also can
be saved, and all BSs broadcast the GTEK at the same time so GTEK can be transmitted in SFN mode.
As we can see BS includes updated GTEK in MBS allocation message or MBS data can introduce so many
advantages, so we propose that BS includes updated GTEK in MBS allocation message or MBS data.
2.3 GAK and GTEK update flow
Here we give the GAK and GTEK update flow in 16m.
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IEEE C802.16m-09/0126
MS
BS
MOB_PAG-ADV (GAK update mode)
RNG-REQ/RSP (GAK)
{Ranging CID (MAC Address): GAK update} M&B TEK
TEK
Grace
Time
MBS_MAP (new GTEK information )
{Broadcast CID: GTEK update mode}
M&B
TEK
Grace
Time
GTEK
Active
Lifetime
MBS_MAP (new GTEK information )
TEK
Grace
Time
Refresh Timeout
GTEK
Active
Lifetime
M&B TEK
Refresh Timeout
{Broadcast CID: GTEK update mode}
M&B
TEK
Grace
Time
GTEK
Active
Lifetime
GTEK
Active
Lifetime
MBS_MAP (new GTEK information )
M&B TEK
Refresh Timeout
{Broadcast CID: GTEK update mode}
TEK
Grace
Time
MOB_PAG-ADV (GAK update mode)
RNG-REQ/RSP (GAK)
{Ranging CID (MAC Address): GAK update}
MBS_MAP (new GTEK information )
TEK
Grace
Time
{Broadcast CID: GTEK update mode}
M&B TEK
Refresh Timeout
M&B
TEK
Grace
Time
GTEK
Active
Lifetime
M&B
TEK
Grace
Time
Figure 1. GAK and GTEK update flow in 16m
BS can .
2. Text Proposal
Remedy 1:
-------- Start of the text proposal --------------------------------------------------------------------------------------3
IEEE C802.16m-09/0126
[Change Line 9 Page 50 in IEEE 802.16m-08/003r6 as following:]
Group AK (GAK) is randomly generated at the ABS. When MS is in idle mode and GAK updates, BS can
page MS one action code to indicate GAK is updated. If MS receives this paging message it may perform
ranging procedure, in ranging procedure MS requests updated GAK in RNG-REQ, and BS includes the updated
GAK in RNG-RSP.
-------- End of proposed text --------------------------------------------------------------------------------------------Remedy 2:
-------- Start of the text proposal --------------------------------------------------------------------------------------[Change Line 17 Page 50 in IEEE 802.16m-08/003r6 as following:]
• Group key update procedure for multicast connection. BS includes updated GTEK in MBS allocation
message, MS can obtain updated GTEK when it decodes MBS allocation message. Alternatively BS can include
updated GTEK in MBS data, MS can obtain updated GTEK when it decodes MBS data.
-------- End of proposed text ---------------------------------------------------------------------------------------------
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