This application is based on European Patent Application No. 07301668.5 filed Dec. 13, 2007, the disclosure of which is hereby incorporated by reference thereto in its entirety, and the priority of which is hereby claimed under 35 U.S.C. §119.
1. Field of the Invention
The present invention generally relates to wireless or mobile communication networks and systems.
Detailed descriptions of such networks and systems can be found in the literature, in particular in Technical Specifications published by standardisation bodies.
2. Description of the Prior Art
An example of such networks and systems, to which the present invention particularly (but not exclusively) applies, uses WiMAX technology. A description of WiMAX technology can be found in particular in IEEE 802.16e and WiMAX Forum standard specifications.
The WiMAX network reference model is recalled in
For the support of Multicast Broadcast Services (MBS), the WiMAX network further comprises an entity called MBS Server, having control and distribution functions for MBS services.
In Multi-BS access mode, as recalled in
The MBS Server is the network element that manages one MBS Zone (has the list of BSs belonging to the MBS Zone). All data traffic dedicated to this MBS Zone goes through this network element. There is one MBS Server per MBS Zone (over possibly several ASNs). The MBS Server functionalities may be located in the ASN-GW or at another place in the network.
The present invention more particularly relates to security handling in such networks and systems.
For example, for WiMAX technology, it is recalled that the MAC layer protocol includes a security sublayer providing authentication, secure key exchange, encryption and integrity control. Privacy Key Management (PKM) protocol, also known as PKMv2, is included in the security sublayer in order to provide secure key distribution from BS to SS. PKMv2 procedures include procedures by which the BS and the SS mutually authenticate themselves, and then the BS provides the authenticated SS with keying material.
PKMv2 procedures performed upon network entry by a MS are recalled in
The present invention more particularly relates to security handling in such networks and systems supporting such MBS Services.
For example, for WiMAX technology, following keying data are defined for MBS services, according to IEEE 802.16e:
Following key derivation functions are defined according to current state of IEEE 802.16e:
MAK=RAND(160)
MGTEK=(RAND 128)
MTK=Dot16KDF(MAK, MGTEK|“MTK”, 128)
The current assumption of the WiMAX Forum and the IEEE is the MAK should be stored in the MS and is common for all MS that are granted for a service (e.g for a TV channel set). However, as recalled above, IEEE 802.16e specification does not define any way to distribute the MAK.
A proposal for MAK distribution is disclosed in the following document: WiMAX Forum Network Working Group (NWG) Contribution MBS High-Level System Architecture Description (Number and file name: 070115_NWG_Huawei_MBS_Section_r2.doc).
This document proposes a WEB based distribution framework where the MS retrieve MAK by making a WEB access. As illustrated in
As recognized by the present invention, such distribution framework where the MS retrieves MAK by making a WEB access has a number of drawbacks, in particular:
The present invention in particular enables to solve part or all of such problems, or to avoid part or all of such drawbacks. More generally, the present invention enables to improve security handling in such systems.
These and other objects are achieved, in one aspect of the present invention, by a method for security handling in a wireless access system supporting Multicast Broadcast Services MBS, said method comprising the steps of:
These and other objects are achieved, in another aspect of the present invention, by a method for security handling in a wireless access system supporting Multicast Broadcast Services MBS, said method comprising the steps of:
These and other objects are achieved, in other aspects of the present invention, by different entities of a wireless access system (such as in particular ASN entity such as Base Station BS or Access Service Network Gateway ASN GW, CSN entity such as MBS Server, Mobile Station MS) for performing a method according to the present invention.
These and other objects of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings:
By way of example, in the following the present invention will more particularly be described in relation with its application to WiMAX technology.
In this example, the present invention may also be explained as follows.
The present invention proposes a flexible framework for subscription to a WiMAX MBS service flow not based on a dedicated MAK proprietary distribution framework, instead of using both MAK (MBS Authorization Key) and MGTEK (Multicast Group Traffic Encryption Key) to cipher MBS channel traffic.
The present invention proposes to avoid use of MAK distribution framework which is out of the scope of WiMAX area.
The present invention proposes to avoid completely usage of MAK and to set statically and permanently MAK in the MS. For example the MAK could be set to 0 in factory; this key is never updated and stay to 0.
The present invention proposes that the MGTEK is then used for both traffic encryption and user content subscription management.
An example of security procedures according to the present invention is illustrated in
In this example, some ASN functionalities are implemented in a BS, while other ASN functionalities are implemented in a ASN GW. However, it should be understood that other examples are possible. In particular, depending on choice for ASN implementation (i.e. Profile A, or Profile B, or Profile C) some ASN functionalities can be implemented either in a BS or in a ASN GW. In general, to cover such different possibilities, the generic term ASN entity will also be used in the present application.
In the example illustrated in
In step 1, the MS performs initial network entry, as defined in IEEE 802.16e.
In step 2, the ASN GW acting as RADIUS authenticator authenticates the MS, according to the procedures recalled in
In step 3, the keys (KEK) for dedicated connections (i.e. for connections others than the one established for MBS service flow) are exchanged, according to the procedures recalled in
In step 4, the MS requests the MGTEK for an MBS service flow, by sending a PKMv2 Key Request message to the BS. Parameters sent in this message include MBS SAID (MBS Security Association Identifier).
In step 5, in another aspect of the present invention, the BS relays this Key Request message to the ASN GW, by sending a message called MBS Access Request to the ASN GW. In the illustrated example, parameters sent in this message include MSSID (Mobile Station Identifier), MBS SAID.
In step 6, in another aspect of the present invention, the ASN GW checks if the MBS Service flow is authorized for the MS, thanks to the subscription data discovered in step 2, and if the MBS service flow is authorized for the MS, then the ASN GW replies to the BS by sending a message called MBS Access Grant. In the illustrated example, parameters sent in this message include MSSID, MBS SAID.
In step 7, the BS sends MGTEK parameters to the MS in a Key Reply message. In the illustrated example, parameters sent in this message include MBS SAID, MGTEK, MGTEK Lifetime, MGTEK SN (MGTEK Sequence Number). Those parameters are ciphered by the KEK which is dedicated to the MS. So other MSs cannot discover the MGTEK associated to the MBS channel during this stage.
Steps 4, 5, 6 and 7 are repeated each time the MGTEK has expired.
If the MS does not have the right to listen the requested MBS Channel then the ANS GW does not reply, and steps 6 and 7 are by-passed. In such condition the MS is not able to listen MBS because it does not have appropriate keying material to do it.
The MGTEK is periodically updated based on a PKMv2 Key request procedure triggered by the MS (this procedure is described in security section of IEEE 802.16e). The Key request procedure is protected by KEK (Key Encryption Key).
In such conditions, when the ASN gateway receives a PKMv2 request for an MBS service, the MSS is authenticated and the ASN GW knows MBS access restrictions associated to this MS. MGTEK is then distributed to this MS function of these restrictions.
In another aspect of the present invention, the MTK is derived from MAK and MGTEK, by using for example the following key derivation functions replacing the above recalled key derivation functions defined according to current state of IEEE 802.16e:
MAK=Constant and never updated (e.g.: set to 0 in factory in the MSS)
MGTEK=(RAND 128)
MTK=Dot16KDF(MAK, MGTEK|“MTK”, 128).
Thus, in one aspect, the present invention proposes a method for security handling in a wireless access system supporting Multicast Broadcast Services MBS, said method comprising the steps of:
In an embodiment, said MBS keying data include an MBS Group Traffic Encryption Key MGTEK.
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises the steps of:
In an embodiment, said steps are repeated upon expiration of a key lifetime.
In an embodiment, said method comprises the steps of:
In the example illustrated in
In step 1′, in another aspect of the present invention, the ASN GW sends a MGTEK Request to the MBS Server. In the illustrated example, this message contains a unique identifier of the multicast channel to be ciphered (formerly it should be an identifier of a security association related to the MBS service: MBS SAID).
In step 2′, in another aspect of the present invention, the MBS Server replies with a MGTEK Response including, in the illustrated example, the value of the MGTEK, the MGTEK lifetime, and the serial number of the MGTEK MGTEK SN. As is the case in the illustrated example, the MBS Server may also include a value of MAK, which could be seen as a way to retrieve factory value of the MAK set in all MSs in case it is not 0.
In step 3′, the ASN GW gives these information to the BSs which broadcast the MBS channel. In the illustrated example, these information are sent in a message Set MGTEK including the same parameters as the MGTEK Response.
In step 4′, the BS acknowledges reception of the message sent in step 3′ by the ASN GW, by sending to the ASN GW a message Set MGTEK Response including, in the illustrated example, MBS SAID.
In the example described in
In the example described in
The scenario according to the example of
The scenario according to the example of
Thus, in another aspect, the present invention proposes a method for security handling in a wireless access system supporting Multicast Broadcast Services MBS, said method comprising the steps of:
In an embodiment, said MBS keying data include an MBS Group Traffic Encryption Key MGTEK.
In an embodiment, said generated MBS keying data include said permanent value of a MBS Authorization Key MAK.
In an embodiment, said method comprises the steps of:
In an embodiment, said steps are repeated upon expiration of a key lifetime.
The present invention in particular has the following advantages:
Additionally there is no specific requirement in the MS as the solution is purely based on IEEE 802.16e radio mechanisms.
In addition to the above described methods, other aspects of the present invention correspond to different entities of a wireless access system (such as in particular Access Service Network ASN entity such as Base Station BS or Access Service Network Gateway ASN GW, Connectivity Service Network CSN entity such as MBS Server) for performing a method according to the present invention.
Thus, another aspect of the present invention is an Access Service Network ASN entity for a wireless access system supporting Multicast Broadcast Services MBS, said ASN entity comprising:
In an embodiment, said Access Service Network ASN entity comprises:
Another aspect of the present invention is an Access Service Network ASN entity for a wireless access system supporting Multicast Broadcast Services MBS, said ASN entity comprising:
In an embodiment, said Access Service Network ASN entity comprises:
Another aspect of the present invention is an Access Service Network ASN entity for a wireless access system supporting Multicast Broadcast Services MBS, said ASN entity comprising:
In an embodiment, said Access Service Network ASN entity comprises:
For these aspects of the present invention regarding an Access Service Network ASN entity:
In an embodiment, said MBS keying data include an MBS Group Traffic Encryption Key MGTEK.
In another embodiment, said ASN entity comprises:
In another embodiment, said ASN entity comprises:
Another aspect of the present invention is a MBS Server for a wireless access system supporting Multicast Broadcast Services MBS, comprising:
In an embodiment, said generated MBS keying data include an MBS Group Traffic Encryption Key MGTEK.
In an embodiment, said generated MBS keying data include a permanent value of a MBS Authorization Key MAK.
Another aspect of the present invention is a Base Station BS, comprising:
In an embodiment, said steps are repeated upon expiration of a key lifetime.
In an embodiment, said Base Station comprises:
In an embodiment, said MBS keying data include an MBS Group Traffic Encryption Key MGTEK.
In an embodiment, said Base Station comprises:
In an embodiment, said MBS keying data include said permanent value of a MBS Authorization Key MAK.
Another aspect of the present invention is an Access Service Network Gateway ASN GW, comprising:
Another aspect of the present invention is an ASN GW comprising:
Another aspect of the present invention is an ASN GW comprising:
In an embodiment, said MBS keying data include an MBS Group Traffic Encryption Key MGTEK.
In an embodiment, said MBS keying data include a permanent value of a MBS Authorization Key MAK.
Another aspect of the present invention is an Access Service Network Gateway ASN GW, comprising:
Another aspect of the present invention is a MBS Server, comprising:
In an embodiment, said generated MBS keying data include an MBS Group Traffic Encryption Key MGTEK.
In an embodiment, said generated MBS keying data include a permanent value of a MBS Authorization Key MAK.
Another aspect of the present invention is a Mobile Station for a wireless access system supporting Multicast Broadcast Services MBS, comprising:
In an embodiment, said Mobile Station comprises:
The detailed implementation of the above-mentioned means does not raise any special problem for a person skilled in the art, and therefore such means do not need to be more fully disclosed than has been made above, by their function, for a person skilled in the art.
Number | Date | Country | Kind |
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07301668.5 | Dec 2007 | EP | regional |