METHOD FOR MANAGING GROUP TRAFFIC ENCRYPTION KEY IN WIRELESS PORTABLE INTERNET SYSTEM

• US 20090235075A1
• Filed: 06/09/2006
• Published: 09/17/2009
• Est. Priority Date: 06/10/2005
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute, Hanaro Telecom., Inc., KT Corporation, Samsung Electronics Co. Ltd., SK Telecom Co., Ltd.
• Original Assignee: Electronics and Telecommunications Research Institute, Hanaro Telecom., Inc., KT Corporation, Samsung Electronics Co. Ltd., SK Telecom Co., Ltd.
• Inventors: Yoon, Chul-Sik, Cho, Seok-Heon
• Granted Patent: US 8,160,254 B2
• Time in Patent Office: Days
• US Class Current: 713/170
• CPC Class Codes: H04L 2209/80 Wireless network architectures or network communication protocols for wireless network security H04W12/00
• CPC Class Codes: H04L 9/0822 using key encryption key
• CPC Class Codes: H04L 9/0833 involving conference or group key network architectures or network communication protocols for key management in group communication in a packet data network H04L63/065
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying

Abstract

The present invention relates to a method for managing a group traffic encryption key (GTEK) in a wireless portable Internet system. In the method, for higher security of a group traffic service such as a multicast service, a broadcast service, and a multicast-broadcast service (MBS), a base station periodically generates and distributes a GTEK to a subscriber station served with the group traffic service. A lifetime of a group key encryption key (GKEK) used for encrypting a GTEK is set greater than that of the GTEK. That is, the GKEK is updated once while the GTEK is updated several times. According to the present invention, security for the group traffic service is increased while reducing radio resource consumption.

Claims

1. A method for updating a group traffic encryption key (GTEK) for a group traffic service in a wireless portable Internet system, the method comprising:

a) determining whether a lifetime of a current group key encryption key (GKEK) used for encrypting a current GTEK expires within a lifetime of the current GTEK;

b) when the lifetime of the current GKEK does expire within the lifetime of the current GTEK, generating a next GTEK and a next GKEK to be used for encrypting the next GTEK within the lifetime of the current GTEK and transmitting the next GTEK and the next GKEK to a subscriber station; and

c) when the lifetime of the current GKEK does not expire within the lifetime of the current GTEK, generating a next GTEK within the lifetime of the current GTEK and transmitting the next GTEK to the subscriber station, wherein the next GTEK is encrypted by using the current GKEK.

2. The method of claim 1, wherein b) comprises:

i) generating the next GKEK during a time interval between the start of the lifetime of the current GTEK and a specific update time;

ii) individually transmitting the next GKEK to subscriber stations served with the group traffic service through a dedicated channel between the subscriber station and a base station;

iii) generating the next GTEK after the above specific update time has expired and encrypting the next GTEK by using the next GKEK; and

iv) transmitting the encrypted next GTEK to all subscriber stations through a broadcasting channel between the subscriber station and the base station.

3. The method of claim 2, wherein the base station sets a lifetime of a GKEK used for encrypting a GTEK to be longer than a lifetime of the GTEK.

4. The method of claim 1, wherein c) comprises:

i) generating the next TEK after a specific update time has passed from the start of the lifetime of the current GTEK and; and

ii) transmitting the next GTEK to all subscriber stations through a broadcasting channel between the subscriber station and the base station.

5. The method of claim 2, wherein the specific update time is set based on a multicast and broadcast (M&

B) TEK Grace Time managed in the base station, and corresponds to a time prior to expiration of the current GTEK lifetime by the amount of the M&

B TEK Grace Time.

6. The method of claim 1, wherein a group key update message for a GKEK update mode used for transmitting the next GKEK generated in b) to each subscriber station served with the group traffic service, a group key update message for a GTEK update mode used for transmitting the next GTEK generated in b) to all subscriber stations, and a group key update message for the GTEK update mode used for transmitting the next GTEK generated in c) to all the subscriber stations are PKMv2 Group-Key-Update-Command messages in the same format.

7. The method of claim 6, wherein the group key update message for the GKEK update mode comprises:

an authorization key (AK) sequence number for identifying an AK used for generating a CMAC-Digest or HMAC-Digest; and

a GKEK-related parameter for transmitting parameters related to a GKEK that is valid in the next GKEK lifetime.

8. The method of claim 6, wherein the group key update message for the GTEK update mode comprises:

a GKEK sequence number for identifying a GKEK used for generating a CMAC-Digest or HMAC-Digest; and

a GTEK-related parameter for transmitting parameters related to a GTEK that is valid in the next GTEK lifetime.

9. The method of claim 7, wherein the group key update message further comprises:

a group security association identity (GSAID) for identifying security association (SA) mapping to a group traffic service;

a key push mode for distinguishing whether the message is the group key update message for the GKEK update mode or is the group key update message for the GTEK update mode;

a key push counter for protecting the message from a replay attack of a malicious attacker; and

a CMAC-Digest or HMAC-Digest for performing a message authentication function.

10. The method of claim 7, wherein the GKEK-related parameter comprises:

a GKEK used for encrypting a GTEK, that is encrypted with a KEK derived from an AK uniquely assigned to each subscriber station, and is transmitted to each subscriber station served with the group traffic service;

a GKEK lifetime for informing of a remaining lifetime of the GKEK; and

a GKEK sequence number for distinguishing between two GKEKs that exist during a GKEK update.

11. The method of claim 8, wherein the GTEK-related parameter comprises:

a GTEK for encrypting traffic data for a group traffic service, and that is encrypted with a GKEK uniquely assigned to each group traffic service and transmitted to the all subscriber stations;

a GTEK lifetime for informing of a remaining lifetime of the GTEK;

a GKEK sequence number for distinguishing between two GKEKs that exist during a GTEK update; and

an associated GKEK sequence number for identifying that which GKEK among the two GKEKs is used for encrypting the respective two GTEKs that exist during a GTEK update, and that is mapped to the corresponding GKEK sequence number.

19. The method of claim 1, wherein when a network node including a group traffic server, a node which requests authentication (Authenticator), or a multicast broadcast server (MBS) generates a GTEK and a GKEK, the network node transmits the GTEK and GKEK to a base station for distribution of the GTEK and GKEK to subscriber stations, wherein the base station assecssing the network node provides the group traffic service to the subscriber stations through a radio channel.

20. The method of claim 19, wherein the network node periodically generates a GTEK and a GKEK and periodically transmits the GTEK and the GKEK to the base station.

21. The method of claim 19, wherein the network node periodically generates a GTEK and a GKEK, and when the base station requests the GTEK or GKEK, the network node transmits the GTEK and GKEK to the base station in response to the request.

12. A method for a base station to update a group traffic encryption key (GTEK) for a group traffic service in a wireless portable Internet system, the method comprising:

a) receiving a GTEK request through a key request message for encrypting a specific group traffic service from a subscriber station;

b) determining whether a GTEK being used for the specific group traffic service exists;

c) when a result of the determination shows that the GTEK being used for encrypting the specific group traffic service does not exist, generating an initial GTEK for encrypting traffic data of the specific group traffic service and an initial group key encryption key (GKEK) for encrypting the initial GTEK, and transmitting the initial GTEK and the initial GKEK to the subscriber station; and

d) when a result of the determination shows that the GTEK being used for encrypting the specific group traffic service exists, transmitting a key reply message including the currently used GTEK and the currently used GKEK for encrypting the current GTEK to the subscriber station, and

wherein a lifetime of the initial GKEK generated in c) is set greater than that of the initial GTEK, and

a lifetime of the GTEK transmitted to the subscriber station in d) and a lifetime of the GKEK respectively correspond to a remaining lifetime of each key.

13. The method of claim 12, wherein the key reply message used for transmitting the GTEK and the GKEK to the subscriber station comprises:

a current GTEK-related parameter that includes parameters related to a GTEK to be used for a lifetime of a current GTEK;

a next GTEK-related parameter that includes parameters related to a GTEK to be used for a lifetime of the next GTEK;

a current GKEK-related parameter that includes parameters related to a GKEK to be used for a lifetime of a current GKEK; and

a next GKEK-related parameter that includes parameters related to a GKEK to be used for a lifetime of the next GKEK.

14. The method of claim 13, wherein, when a subscriber station requests the GTEK before a specific update time passes since the start of a lifetime of the GTEK, wherein the subscriber station requests the specific group traffic service so to be served with the service for the first time, the base station transmits a key reply message including the current GTEK-related parameter and the current GKEK-related parameter to the subscriber station.

15. The method of claim 13, wherein, when a subscriber station requests the GTEK after a specific update time has passed since the start of a lifetime of the GTEK, and a lifetime of the current GKEK expires within a lifetime of the current GTEK, wherein the subscriber station requests the speficie group traffic service so as to be served with the service for the first time, the base station transmits a key reply message including the current GTEK-related parameter, the current GKEK-related parameter, the next GTEK-related parameter, and the next GKEK-related parameter to the subscriber station.

16. The method of claim 13, wherein, when a subscriber station requests the GTEK after a specific update time has passed since the start of a lifetime of the GTEK, and a lifetime of the current GKEK does not expire within a lifetime of the current GTEK, wherein the subscriber station requests the specific group traffic service so as to be served with the service for the first time, the base station transmits a key reply message including the current GTEK-related parameter, the current GKEK-related parameter, and the next GTEK-related parameter to the subscriber station.

17. The method of claim 13, wherein when a subscriber station requests the GTEK after a specific update time has passed since the start of a lifetime of the GTEK, and a lifetime of the current GKEK expires within a lifetime of the current GTEK, wherein the subscriber station has already been served with the specific group traffic service, the base station transmits a key reply message including the next GTEK-related parameter, and the next GKEK-related parameter to the subscriber station

18. The method of claim 13, wherein when a subscriber station requests the GTEK after a specific update time has passed since the start of a lifetime of the GTEK, and a lifetime of the current GKEK does not expire within a lifetime of the current GTEK, wherein the subscriber station has already been served with the group specific traffic service, the base station transmits a key reply message including the next GTEK-related parameter to the subscriber station.