Method for performing authenticated handover in a wireless local area network

• US 20060083200A1
• Filed: 10/07/2005
• Published: 04/20/2006
• Est. Priority Date: 10/15/2004
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Emeott, Stephen P., Braskich, Anthony J.
• Granted Patent: US 7,236,477 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04L 2209/80 Wireless network architectures or network communication protocols for wireless network security H04W12/00
• CPC Class Codes: H04L 2463/061 applying further key derivation, e.g. deriving traffic keys from a pair-wise master key cryptographic mechanisms or cryptographic arrangements for generation of secret information including derivation or calculation of cryptographic keys or passwords H04L9/0861
• CPC Class Codes: H04L 63/061 for key exchange, e.g. in peer-to-peer networks cryptographic mechanisms or cryptographic arrangements for key agreement H04L9/0838
• CPC Class Codes: H04L 9/083 involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]
• CPC Class Codes: H04L 9/321 involving a third party or a trusted authority
• CPC Class Codes: H04W 12/041 Key generation or derivation
• CPC Class Codes: H04W 12/0431 Key distribution or pre-distribution; Key agreement
• CPC Class Codes: H04W 12/0433 Key management protocols
• CPC Class Codes: H04W 12/062 Pre-authentication
• CPC Class Codes: H04W 12/068 using credential vaults, e.g. password manager applications or one time password [OTP] applications
• CPC Class Codes: H04W 12/08 Access security
• CPC Class Codes: H04W 36/0016 Hand-off preparation specially adapted for end-to-end data sessions
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A wireless local area network system (100) supporting mobile radio telephony reduces the time to complete an authenticated handover from one access point (104) to another (108) by a mobile station (102) by performing some of the steps normally performed upon leaving one access point while still associated with that access point. More particularly, the mobile station causes a cryptographic key (204) to be preestablished (212) for use when handing over to a new access point. The cryptographic key is derived at the mobile station, and is also derived in the WLAN infrastructure and stored until the mobile station initiates a handover.

Claims

1. A method for performing authenticated handover in a wireless local area network (WLAN) by a mobile station, comprising:

while associated with a first access point;

obtaining a fast handoff master key from an authentication server associated with the WLAN;

calculating a pairwise master key and a pairwise master key identifier from the master key;

obtaining a list of ANonce values and neighbor access point identifiers from the first access point, where each ANonce value is unique and associated with one neighbor access point;

deciding to handover to a second access point, the second access point being a neighbor access point of the first access point;

upon deciding to handover to the second access point, transmitting a reassociation request to the second access point, the reassociation request including the pairwise master key identifier and an SNonce value;

receiving from the second access point a reassociation response including an indication that the second access point has acquired the pairwise master key;

calculating a pairwise temporary key based on the pairwise master key, SNonce value, and ANonce value associated with the second access point on the list of ANonce values obtained from the first access point;

installing the pairwise temporary key; and

commencing service with the second access point using the pairwise temporary key.

2. A method for performing authenticated handover as defined in claim 1, further comprising performing an integrity check of the pairwise temporary key with the second access point, performed before installing the pairwise temporary key.

3. A method of performing authenticated handover from a first access point to a second access point by a mobile station in a wireless local area network, the second access point being a neighbor access point of the first access point, the method comprising:

preauthenticating a first cryptographic key with an authentication server in the WLAN;

receiving a list of neighbor access points and associated access point cryptographic values from the first access point;

deriving a second cryptographic key from the first cryptographic key according to a predefined computation;

deriving a second cryptographic key identifier from the second cryptographic key;

deciding to reassociate with the second access point;

transmitting a reassociation request to the second access point, including a key identifier associated with the master key and a station cryptographic value;

receiving a reassociation response from the second access point including an indication that the second access point has acquired the second cryptographic key;

deriving a session cryptographic key from the second cryptographic key, station cryptographic value, and access point cryptographic value associated with the second access point on the list of neighbor access points acquired from the first access point; and

installing the session cryptographic key for use while communicating with the second access point.

4. A method for performing authenticated handover in a wireless local area network (WLAN) by a mobile station from a first access point to a second access point, the second access point being a neighbor access point of the first access point, the method comprising:

while the mobile station is associated with the first access point;

generating a first cryptographic key at an authentication server in the WLAN in response to an authentication request by the mobile station;

distributing the first cryptographic key to the mobile station and an acting key depository coupled to the WLAN;

calculating a second cryptographic key based on the first cryptographic key at the mobile station and acting key depository;

receiving a reassociation request at the second access point including a second cryptographic key identifier;

acquiring the second cryptographic key from the key depository;

transmitting a confirmation to the mobile station indicating the second access point is in possession of the second cryptographic key;

deriving a session key at the mobile station and the second access point based on the second cryptographic key;

installing the session key at the mobile station and the second access point; and

commencing service between the second access point and the mobile station using the session key for secure communication.

5. The method of performing authenticated handover as defined in claim 4, wherein the acting key depository is the first access point.

6. The method of performing authenticated handover as defined in claim 4, wherein the acting key depository is a stand alone network entity.

7. The method of performing authenticated handover as defined in claim 4, further comprising:

generating a list of access point cryptographic values at the first access point, wherein one access point cryptographic value is generated for each neighbor access point of the first access point, and where each one of the access point cryptographic values is associated with one neighbor access point; and

transmitting the list of access point cryptographic values and associated access point identifiers to the mobile station.

8. The method of performing authenticated handover as defined in claim 4, wherein receiving the reassociation request includes a station cryptographic value, the session key is generated using the station cryptographic value.

9. The method of performing authenticated handover as defined in claim 4, wherein transmitting the confirmation is performed in response to the second access point having the second cryptographic key cached at the second access point.

10. A method for performing authenticated handover in a wireless local area network (WLAN) by a mobile station, comprising:

while associated with a first access point;

obtaining key material from an authentication server associated with the WLAN;

calculating a pairwise master key from the key material;

obtaining a list of ANonce values and neighbor access point identifiers from the first access point, where each ANonce value is unique and associated with one neighbor access point;

deciding to handover to a second access point, the second access point being a neighbor access point of the first access point;

upon deciding to handover to the second access point, transmitting a reassociation request to the second access point, the reassociation request including a pairwise master key identifier calculated from the pairwise master key and an SNonce value;

receiving from the second access point a reassociation response including an indication that the second access point has acquired the pairwise master key;

calculating a pairwise temporary key based on the pairwise master key, SNonce value, and ANonce value associated with the second access point on the list of ANonce values obtained from the first access point;

installing the pairwise temporary key; and

commencing service with the second access point using the pairwise temporary key.

11. A method for performing authenticated handover as defined in claim 10, further comprising performing an integrity check of the pairwise temporary key with the second access point, performed before installing the pairwise temporary key.

12. A method of performing authenticated handover from a first access point to a second access point by a mobile station in a wireless local area network, the second access point being a neighbor access point of the first access point, the method comprising:

obtaining a cryptographic key

receiving a list of neighbor access points and associated access point cryptographic values from the first access point;

deciding to reassociate with the second access point;

deriving a cryptographic key identifier from the cryptographic key;

transmitting a reassociation request to the second access point, including a key identifier associated with the cryptographic key and a station cryptographic value;

receiving a reassociation response from the second access point including an indication that the second access point has acquired the cryptographic key;

deriving a session cryptographic key from the cryptographic key, station cryptographic value, and access point cryptographic value associated with the second access point on the list of neighbor access points acquired from the first access point; and

installing the session cryptographic key for use while communicating with the second access point.

13. The method of performing authenticated handover defined in claim 12 wherein obtaining the cryptographic key involves preauthenticating with an authentication server in the WLAN.

14. The method of performing authenticated handover defined in claim 13 wherein obtaining the cryptographic key involves retrieving the cryptographic key from a cache of stored cryptographic keys

15. A method for performing authenticated handover in a wireless local area network (WLAN) by a mobile station from a first access point to a second access point, the second access point being a neighbor access point of the first access point, the method comprising:

while the mobile station is associated with the first access point;

generating a cryptographic key at an authentication server in the WLAN in response to an authentication request by the mobile station;

distributing the cryptographic key to an acting key depository coupled to the WLAN;

receiving a reassociation request at the second access point including a cryptographic key identifier;

acquiring the cryptographic key from the key depository;

transmitting a confirmation to the mobile station indicating the second access point is in possession of the cryptographic key;

deriving a session key at the mobile station and the second access point based on the second cryptographic key;

installing the session key at the mobile station and the second access point; and

commencing service between the second access point and the mobile station using the session key for secure communication.

16. The method of performing authenticated handover as defined in claim 15, wherein the acting key depository is the first access point.

17. The method of performing authenticated handover as defined in claim 16, wherein the acting key depository is a stand alone network entity.

18. The method of performing authenticated handover as defined in claim 16, wherein the step of acquiring the cryptographic key from the key depository is a result of a request from the second access point.

19. The method of performing authenticated handover as defined in claim 16, wherein acquiring the cryptographic key from the key depository is a result of the key depository independently distributing the cryptographic key.

20. The method of performing authenticated handover as defined in claim 16, further comprising:

generating a list of access point cryptographic values at the first access point, wherein one access point cryptographic value is generated for each neighbor access point of the first access point, and where each one of the access point cryptographic values is associated with one neighbor access point; and

transmitting the list of access point cryptographic values and associated access point identifiers to the mobile station.

21. The method of performing authenticated handover as defined in claim 20 wherein generating the list of access point cryptographic values at the first access point also includes generating a cryptographic value that is not associated with a neighbor access point

22. The method of performing authenticated handover as defined in claim 16, wherein receiving the reassociation request includes a station cryptographic value, the session key is generated using the station cryptographic value.