System and Method for Securing Wireless Communications

• US 20120106739A1
• Filed: 11/03/2010
• Published: 05/03/2012
• Est. Priority Date: 11/03/2010
• Status: Active Grant

• Current Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Inventors: Blankenship, Yufei, Liu, Tie, Ly, Hung D.
• Granted Patent: US 8,744,082 B2
• Time in Patent Office: Days
• US Class Current: 380/270
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• 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 63/1475 Passive attacks, e.g. eavesdropping or listening without modification of the traffic monitored
• CPC Class Codes: H04L 9/0875 based on channel impulse response [CIR]
• 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 12/65 Environment-dependent, e.g. using captured environmental data

Abstract

A system and method for securing wireless communications are provided. A method for secure communications by a first user includes estimating a channel between the first user and a second user based on a pilot signal transmitted by the second user, determining a first threshold and a second threshold based on the estimate of channel, selecting a first subset of channel estimates, signaling the first subset of channel estimates to the second user, receiving a second subset of channel estimates from the second user, for each channel estimate in the second subset of channel estimates, quantizing the channel estimate based on a relationship between a gain of the channel estimate and the first threshold and the second threshold, generating a first secret key based on quantized channel estimates, verifying that the first secret key matches a second secret key generated by the second user, and transmitting information to the second user.

Claims

1. A method for secure communications by a first user, the method comprising:

estimating a channel between the first user and a second user, thereby producing a first channel estimate comprising a first gain estimate and a first phase estimate of the channel;

transmitting a first public information regarding the first channel estimate to the second user; and

generating a first block of secret bits based on the first channel estimate.

2. The method of claim 1, further comprising determining the first public information.

3. The method of claim 2, wherein determining the first public information comprises:

selecting a set of one or more time instances from which the first user produces the first channel estimate; and

setting an indicator of the selected set of one or more time instances as the first public information.

4. The method of claim 3, wherein determining the first public information further comprises:

selecting a group of phase quantization bins from a plurality of groups of phase quantization bins; and

selecting an indicator of the selected group of phase quantization bins as an additional component of the first public information.

5. The method of claim 3, wherein selecting a set of one or more time instances comprises:

determining a first threshold and a second threshold;

selecting a set of channel estimates, wherein the set of channel estimates comprises M or more consecutive channel estimates with gain estimates that are all less than the first threshold or all more than the second threshold, where M is a positive integer value; and

selecting the time instances corresponding to the selected set of channel estimates.

6. The method of claim 5, wherein generating a first block of secret bits comprises for each channel estimate in the selected set of channel estimates, quantizing the channel estimate based on a relationship between a gain estimate of the channel estimate and the first threshold and the second threshold to produce the first block of secret bits.

7. The method of claim 6, wherein quantizing the channel estimate comprises:

determining if the gain estimate of the channel estimate is less than the first threshold or if the gain estimate of the channel estimate is more than the second threshold;

quantizing the gain estimate of the channel estimate to produce the first block of secret bits if the gain estimate of the channel estimate is less than the first threshold; and

quantizing the gain estimate of the channel estimate and a phase estimate of the channel estimate to produce the first block of secret bits if the gain estimate of the channel estimate is more than the second threshold.

8. The method of claim 7, wherein quantizing the phase estimate of the channel estimate comprises:

selecting a group of phase quantization bins from a plurality of groups of phase quantization bins;

mapping the phase estimate of the channel to a codeword, wherein the codeword is associated with a quantization bin in the selected group of phase quantization bins; and

selecting at least a portion of the codeword as part of the first block of secret bits.

9. The method of claim 1, further comprising receiving a second public information from the second user, and wherein the generating the first block of secret bits is further based on the second public information.

10. The method of claim 9, wherein the second public information comprises a subset of the first public information.

11. The method of claim 10, wherein the second public information comprises one or more time instances where the second user selects to generate a second block of secret bits.

12. The method of claim 11, wherein the second user generates a second block of secret bits based on a second channel estimate, wherein the second channel estimate comprises a second gain estimate and a second phase estimate.

13. The method of claim 11, wherein the generating the first block of secret bits comprises generating the first block of secret bits within time instances of the second public information.

14. A method for secure communications by a second user, the method comprising:

receiving a first public information from a first user;

estimating a channel between the second user and the first user, thereby producing a second channel estimate comprising a second gain estimate and a second phase estimate of the channel; and

generating a second block of secret bits based on the first public information and the second gain estimate and the second phase estimate of the channel.

15. The method of claim 14, wherein the second user produces a second public information based on the second channel estimate, and transmits the second public information to the first user.

16. The method of claim 15, wherein the generating the second block of secret bits is based on the second public information.

17. The method of claim 14, wherein the first public information comprises an indication of a set of one or more time instances when the second user performs the channel estimation.

18. The method of claim 16, wherein the generating a second block of secret bits comprises:

determining a first threshold and a second threshold; and

quantizing a set of channel estimates indicated by the second public information based on a relationship between a gain estimate of the channel estimate and the first threshold and the second threshold to produce the second block of secret bits.

19. The method of claim 18, wherein quantizing a set of channel estimates indicated by the second public information based on a relationship between a gain estimate of the channel estimate and the first threshold and the second threshold comprises:

determining if the gain estimate of the channel estimate is less than the first threshold or if the gain estimate of the channel estimates is more than the second threshold;

quantizing the gain estimate of the channel estimate if the gain estimate of the channel estimate is less than the first threshold; and

quantizing the gain estimate of the channel estimate and a phase estimate of the channel estimate if the gain estimate of the channel estimate is more than the second threshold.

20. The method of claim 19, wherein quantizing the phase estimate of the channel estimate comprises:

selecting a group of phase quantization bins from a plurality of groups of phase quantization bins;

mapping the phase estimate of the channel to a codeword, wherein the codeword is associated with a quantization bin in the selected group of phase quantization bins; and

selecting all or a portion of the codeword as part of the second block of secret bits.

21. A communications device comprising:

a channel estimate unit configured to estimate a channel between the communications device and a remote communications device;

a threshold unit coupled to the channel estimate unit, the threshold unit configured to determine one or more thresholds based on the channel estimate;

a channel select unit coupled to the channel estimate unit, the channel select unit configured to select channel estimates; and

a key generate unit coupled to the channel estimate unit, the key generate unit configured to generate secret bits based on a gain of the channel estimate and a phase of the channel estimate.

22. The communications device of claim 21, wherein the key generate unit generates the secret bits based on a relationship between a gain of the channel estimate and the one or more thresholds.

23. The communications device of claim 22, wherein the key generate unit comprises:

a phase quantizer configured to quantize a phase of a channel estimate;

a gain quantizer configured to quantize a gain of a channel estimate;

a key generator unit coupled to the phase quantizer and to the gain quantizer, the key generator unit configured generate the secret bits based on a codeword produced by the phase quantizer and/or the gain quantizer; and

a comparison unit coupled to the phase quantizer and to the gain quantizer, the comparison unit configured to compare the gain of the channel estimate with the one or more thresholds and to generate a control signal based on the comparison.

24. The communications device of claim 21, further comprising an encrypt/decrypt unit coupled to the key generate unit, the encrypt/decrypt unit configured to encode transmissions to the remote communications device with the secret bits.

25. The communications device of claim 21, wherein the key generate unit is configured to select a group of phase quantization bins from a plurality of groups of phase quantization bins, to map a first phase estimate of the channel to a codeword, wherein the codeword is associated with a quantization bin in a selected group of phase quantization bins, and select at least a portion of the codeword as a part of the secret bits.

26. A device for secure communications, the device comprising:

a channel estimator configured to estimate a channel between the device and a second device, thereby producing a first channel estimate comprising a first gain estimate and a first phase estimate of the channel;

a transmitter configured to transmit a first public information regarding the first channel estimate to the second device; and

a generator configured to generate a first block of secret bits based on the first channel estimate.

27. The device of claim 26, further comprising a determining unit configured to determine the first public information by selecting a set of one or more time instances from which the device produces the first channel estimate and setting an indicator of the selected set of one or more time instances as the first public information.

28. The device of claim 27, wherein the determining unit determines the first public information by selecting a group of phase quantization bins from a plurality of groups of phase quantization bins and selecting an indicator of the selected group of phase quantization bins as an additional component of the first public information.

29. The device of claim 27, further comprising a receiving unit configured to receive a second public information from the second device, and wherein the generator is configured to generate the first block of secret bits based on the second public information.

30. A device for secure communications, the device comprising:

a receiver, configured to receive a first public information from a second device;

a channel estimator, configured to estimate a channel between the second device and the device, thereby producing a second channel estimate comprising a second gain estimate and a second phase estimate of the channel; and

a generator, configured to generate a second block of secret bits based on the first public information and the second gain estimate and the second phase estimate of the channel.

31. The device of claim 30, further comprising an information producer configured to produce a second public information based on the second channel estimate, the second public information to be transmitted to the second device.

32. The device of claim 30, wherein the first public information comprises an indication of a set of one or more time instances when the channel estimator performs the channel estimation.