Simplified CCMP mode for a wireless local area network

• US 7,523,306 B2
• Filed: 11/21/2003
• Issued: 04/21/2009
• Est. Priority Date: 01/16/2003
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Liang, Jie
• Primary Examiner(s): Barren, Jr.; Gilberto
• Assistant Examiner(s): SAN JUAN, MARTINJERIKO P
• Application Number:
  US10/718,889
• Publication Number:
  US 20040142710A1
• Time in Patent Office: 1,978 Days
• Field of Search: None
• US Class Current: 713/161
• CPC Class Codes: H04L 63/123 received data contents, e.g. message integrity
• CPC Class Codes: H04L 63/1441 Countermeasures against malicious traffic countermeasures against attacks on cryptographic mechanisms H04L9/002
• CPC Class Codes: H04W 12/106 Packet or message integrity
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A system and method for generating a message integrity code, MIC, for a MAC protocol data unit in a wireless local area network, WLAN, operating according to the IEEE 802.11 standard. A MAC service data unit, MSDU, sequence control sequence number, SN, input to the MIC algorithm is suppressed, e.g. set to all zeros, when calculating the MIC. Only the fragment number, FN, portion of the sequence control is included in calculation of the MIC. The MIC may therefore be calculated before an actual SN has been determined. All MPDUs include sequential packet numbers, PNs. A station receiving MPDUs checks the PNs of MPDUs having the same SN, and rejects messages which do not have a proper sequential set of PNs.

Claims

1. A method for generating a message integrity code in a wireless local area network operating under an IEEE 802.11 standard, comprising:

separate a message into a plurality of fragments;

suppressing a sequence number input to a message integrity code (MIC) algorithm;

calculating a message integrity code based in part on a fragment number;

encrypting the MIC without the sequence number;

assigning packet numbers to message fragments in the order of fragmentation;

assigning a sequence number to the message which is the same for each message fragments; and

transmitting the message to a receiving station by a transmitter.

2. A method according to claim 1, further comprising, upon receipt of a plurality of messages having the same sequence number at a receiving station, checking the received packet numbers for a complete sequence.

3. A method according to claim 2, further comprising rejecting a message if it does not have a complete sequence of packet numbers.

4. In a wireless local area network message protocol in which each data unit is assigned a sequence number and a fragment number, a method of generating a message integrity code (MIC) a data unit comprising:

using the fragment number, but not the sequence number as an input to a message integrity code (MIC) algorithm; and

generating the MIC before the sequence number has been assigned to a packet.

5. The method of claim 4, further comprising assigning a packet number to each message fragment, receiving messages at a receiving station and checking packet numbers of received message for a complete sequence of packet numbers.

6. The method of claim 5, further comprising rejecting messages which do not have a complete sequence of packet numbers.

7. A method for providing security for messages transmitted over a wireless local area network, wherein the messages have a transmitted message integrity code (MIC) encrypted without a sequence number and assigned packet numbers to message fragments in the order of fragmentation, said method comprising:

receiving, by a receiver, a plurality of messages with the same sequence number; and

checking the packet numbers of each of the plurality of messages in the order received to determine whether the plurality of messages include a complete sequence of packet numbers.

8. A method according to claim 7, further comprising:

upon receipt of a message, calculating a received message integrity code based in part on the fragment number for the received message.

9. A method according to claim 8, further comprising:

comparing the transmitted message integrity code to the received message integrity code.

10. A method according to claim 9, further comprising:

rejecting the received message if the transmitted message integrity code does not match the received message integrity code.

11. A method according to claim 7, further comprising:

if the plurality of messages has an incomplete sequence of packet numbers, rejecting the messages identified by the sequence number.

12. A wireless network station comprising a processor programmed to:

suppress a sequence number input to a message integrity code (MIC) algorithm;

calculate a message integrity code based in part on a fragment number;

encrypt the MIC without the sequence number;

assign a packet number to each message fragment in the order of fragmentation; and

assign a sequence number to the message which is the same for each message fragments.

13. A wireless network station according to claim 12 wherein the processor is programmed to:

transmit a message including the message integrity code over a wireless local area network.

14. A wireless network station according to claim 12 wherein the processor is programmed to:

receive a message including a message integrity code over a wireless local area network;

suppress a sequence number input to a message integrity code algorithm; and

calculate a message integrity code for the received message based in part on a fragment number.

15. A wireless network station according to claim 14 wherein the processor is programmed to:

compare the message integrity code of the received message to the message integrity code calculated for the received message; and

if the message integrity code of the received message does not match the message integrity code calculated for the received message, reject the received message.

16. A wireless network station according to claim 14 wherein the processor is programmed to:

upon receipt of a plurality of messages having a common sequence number, check packet numbers of the messages for a complete sequence; and

if the packet number sequence is not complete, reject all of the received with the common sequence number.

17. A wireless network station comprising a processor programmed to:

assign sequence numbers to all messages in the order of transmission and include the sequence number in each transmitted message;

assign fragment numbers to all messages in the order of fragmentation of each message and include the fragment number in each transmitted message; and

calculate a transmitted message integrity code based in part on the fragment number for each transmitted message and include the transmitted message integrity code in each transmitted message.

18. A wireless network station according to claim 17 wherein the processor is programmed to:

upon receipt of a message, calculate a received message integrity code based in part on the fragment number for the received message;

compare the transmitted message integrity code to the received message integrity code; and

reject the received message if the transmitted message integrity code does not match the received message integrity code.

19. A wireless network station according to claim 17 wherein the processor is programmed to:

upon receiving a plurality of messages having the same sequence number, check the packet numbers of each of the plurality of messages to determine whether the plurality of messages include a complete sequence of packet numbers; and

if the plurality of messages has an incomplete sequence of packet numbers, reject the messages identified by the sequence number.