802.11 using a compressed reassociation exchange to facilitate fast handoff

• US 7,350,077 B2
• Filed: 04/17/2003
• Issued: 03/25/2008
• Est. Priority Date: 11/26/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Meier, Robert, Smith, Douglas, Rebo, Richard D., Winget, Nancy Cam, Griswold, Victor J.
• Primary Examiner(s): Zand; Kambiz
• Assistant Examiner(s): Tolentino; Roderick
• Application Number:
  US10/417,653
• Publication Number:
  US 20040103282A1
• Time in Patent Office: 1,804 Days
• Field of Search: 713/171, 713/168, 370/338
• US Class Current: 713/171
• CPC Class Codes: G06Q 20/3674 involving authentication
• CPC Class Codes: H04L 2209/80 Wireless
• CPC Class Codes: H04L 2463/061 applying further key derivation, e.g. deriving traffic keys from a pair-wise master key
• CPC Class Codes: H04L 63/06 for supporting key management in a packet data network cryptographic mechanisms or cryptographic arrangements for key management H04L9/08
• CPC Class Codes: H04L 63/08 for authentication of entities cryptographic mechanisms or cryptographic arrangements for entity authentication H04L9/32
• CPC Class Codes: H04L 9/0836 using tree structure or hierarchical structure
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying
• CPC Class Codes: H04W 12/04 Key management, e.g. using generic bootstrapping architecture [GBA]
• CPC Class Codes: H04W 12/062 Pre-authentication
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: Y10S 707/99945 Object-oriented database structure processing
• CPC Class Codes: Y10S 707/99948 Application of database or data structure, e.g. distributed, multimedia, or image

Abstract

A method and system for handling roaming mobile nodes in a wireless network. The system uses a Subnet Context Manager to store current Network session keys, security policy and duration of the session (e.g. session timeout) for mobile nodes, which is established when the mobile node is initially authenticated. Pairwise transit keys are derived from the network session key. The Subnet Context Manager handles subsequent reassociation requests. When a mobile node roams to a new access point, the access point obtains the network session key from the Subnet Context Manager and validates the mobile node by computing a new pairwise transient key from the network session key.

Claims

1. A method for establishing a secure association for a mobile node with a network, the steps comprising:

associating with an access point;

authenticating the mobile node using an extensible authentication protocol by the access point;

establishing a network session key; and

wherein the network session key is used to establish a key request key and a base transient key;

wherein the base transient key is used as a counter mode key generator to provide fresh pairwise transient keys;

wherein the key request key is used by the mobile node to prove it has proper authorization for a session;

wherein roaming after establishing the network session key comprises;

incrementing a rekey number, producing an incremented rekey number,

generating a fresh pairwise transient key based on the incremented rekey number;

sending a reassociation request to a new access point, the reassociation request containing the incremented rekey number, and

verifying the new access point is using the fresh pairwise transient key based on the incremented rekey number.

2. The method of claim 1 further comprising sending the network session key to a Subnet Context Manager.

3. The method of claim 1 wherein the extensible authentication protocol is 802.1X compliant.

4. The method of claim 1 further comprising authenticating key refreshes using the key request key.

5. The method of claim 4 further comprising deriving a pairwise transient keys using the base transient key.

6. The method of claim 1 further comprising delivering the group transient key in the re-association request to compress and optimize messages.

7. The method of claim 1 further comprising computing a Key Request Key and a Base Transient Key from the network session key using a pseudo random function.

8. The method of claim 1 further comprising sending a re-association request, the re-association request comprising a rekey request number and an authenticated element.

9. The method of claim 8 further comprising verifying the rekey request number of the re-association request is greater than a previous rekey request number.

10. The method of claim 8 wherein the re-association request further comprises replay protection.

11. The method of claim 10 wherein the replay protection comprises a timestamp.

12. The method of claim 10 wherein the replay protection comprises a random challenge.

13. The method of claim 8 wherein the authenticated element authenticates a security policy defined by the mobile node.

40. A method according to claim 1, the verifying step further comprises retrieving group transient key from the new access point using the fresh pairwise key.

41. A method according to claim 1, further comprising

the reassociation request further comprising a mobile node identification and an authentication element;

validating the current security association to the network by use of the key request key; and

the verifying step further comprising receiving a response from the new access point, the response comprising an authentication element, the authentication element comprising delivery of a new group transient key, and proof of possession of the fresh pairwise transient key by using the new pairwise transient key to authenticate the element.

42. The method according to claim 1, wherein roaming comprises a rekey sequence, the rekey sequence comprising:

computing an authentication element, the authentication element comprising a rekey request number and the fresh pairwise transient key;

transmitting to the new access point a call for a new pairwise transient key and alerting the new access point that the mobile node is ready to receive and transmit using the fresh pairwise transient key;

receiving a response authentication element from the new access point; and

the verifying step comprises verifying the response authentication element comprises the fresh pairwise transient key and receipt of the group transient key.

14. A mobile node, comprising:

means for associating with an access point;

means for authenticating the mobile node using an extensible authentication protocol by the access point;

means for establishing a network session key; and

wherein the network session key is used to establish a key request key and a base transient key;

wherein the base transient key is used as a counter mode key generator to provide fresh pairwise transient keys;

wherein the key request key is used by the mobile node to prove it has proper authorization for a session; and

means for roaming, the means for roaming comprises means for incrementing a rekey number, producing an incremented rekey number, means for generating a fresh pairwise transient key based on the incremented rekey number, means for sending a reassociation request to a new access point, the new reassociation request containing the incremented rekey number, and means for verifying the new access point is using the fresh pairwise transient key based on the incremented rekey number.

15. The mobile node of claim 14 further comprising means for sending the network session key to a Subnet Context Manager.

16. The mobile node of claim 14 wherein the extensible authentication protocol is 802.1X compliant.

17. The mobile node of claim 14 further comprising means for authenticating key refreshes using the key request key.

18. The mobile node of claim 17 further comprising means for deriving a pairwise transient keys using the base transient key.

19. The mobile node of claim 14 further comprising means for delivering the group transient key in the re-association request to compress and optimize messages.

20. The mobile node of claim 14 further comprising means for computing a Key Request Key and a Base Transient Key from the network session key using a pseudo random function.

21. The mobile node of claim 14 further comprising means for sending a re-association request, the re-association request comprising a rekey request number and an authenticated element.

22. The mobile node of claim 21 further means for comprising verifying the rekey request number of the re-association request is greater than a previous rekey request number.

23. The mobile node of claim 21 wherein the means for re-association request further comprises means for replay protection.

24. The mobile node of claim 23 wherein the means for replay protection comprises means for using a timestamp.

25. The mobile node of claim 23 wherein the means for replay protection comprises means for a random challenge.

26. The mobile node of claim 21 wherein the authenticated element authenticates a security policy defined by the mobile node.

27. A computer program product having a computer readable medium having computer program logic recorded thereon for establishing a secure association for a mobile node with a network, comprising means for associating with an access point;

means for authenticating the computer readable instructions using an extensible authentication protocol by the access point;

means for establishing a network session key; and

wherein the network session key is used to establish a key request key and a base transient key;

wherein the base transient key is used as a counter mode key generator to provide fresh Pairwise transient keys;

wherein the key request key is used by the computer readable instructions to prove it has proper authorization for a session; and

means for roaming, the means for roaming comprises means for incrementing a rekey number, producing an incremented rekey number, means for generating a fresh pairwise transient key based on the incremented rekey number, means for sending a reassociation request to a new access point, the new reassociation request containing the incremented rekey number, and means for verifying the new access point is using the fresh pairwise transient key based on the incremented rekey number.

28. The computer program product of claim 27 further comprising means for sending the network session key to a Subnet Context Manager.

29. The computer program product of claim 27 wherein the extensible authentication protocol is 802.1X compliant.

30. The computer program product of claim 27 further comprising means for authenticating key refreshes using the key request key.

31. The computer program product of claim 30 further comprising means for deriving a pairwise transient keys using the base transient key.

32. The computer program product of claim 27 further comprising means for delivering the group transient key in the re-association request to compress and optimize messages.

33. The computer program product of claim 27 further comprising means for computing a Key Request Key and a Base Transient Key from the network session key using a pseudo random function.

34. The computer program product of claim 27 further comprising means for sending a re-association request, the re-association request comprising a rekey request number and an authenticated element.

35. The computer program product of claim 34 further means for comprising verifying the rekey request number of the re-association request is greater than a previous rekey request number.

36. The computer program product of claim 34 wherein the means for re-association request further comprises means for replay protection.

37. The computer program product of claim 36 wherein the means for replay protection comprises means for using a timestamp.

38. The computer program product of claim 36 wherein the means for replay protection comprises means for a random challenge.

39. The computer program product of claim 34 wherein the authenticated element authenticates a security policy defined by the computer program product.