System and method for securing wireless communications

• US 8,744,082 B2
• Filed: 11/03/2010
• Issued: 06/03/2014
• 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: Ly, Hung D., Blankenship, Yufei, Liu, Tie
• Primary Examiner(s): Patel, Ashok
• Assistant Examiner(s): GRACIA, GARY S
• Application Number:
  US12/938,841
• Publication Number:
  US 20120106739A1
• Time in Patent Office: 1,308 Days
• Field of Search: 380/270, 375/222, 375/226, 375/269, 375/273, 375/308, 341/54, 370/516
• 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, by a processor, 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;

determining, by the processor, first public information, comprising;

selecting a set of one or more time instances from which the first user produces the first channel estimate, wherein selecting the 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 time instances corresponding to the selected set of channel estimates; and

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

transmitting, by a transmitter, the first public information regarding the first channel estimate to the second user;

determining, by the processor, whether to use only the first gain estimate to generate a first block of secret bits, or to use both the first gain estimate and the first phase estimate to generate the first block of secret bits; and

generating, by the processor, the first block of secret bits using the first channel estimate,

wherein the generating comprises using the first gain estimate without the first phase estimate to generate the first block of secret bits, when the first gain estimate is less than the first threshold, and

wherein the generating comprises using the first gain estimate and the first phase estimate to generate the first block of secret bits, when the first gain estimate is more than the second threshold, wherein the first threshold is lower than the second threshold.

2. The method of claim 1, 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.

3. The method of claim 1, wherein generating a first block of secret bits comprises for each channel estimate in the selected set of channel estimates, quantizing the channel estimate using 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.

4. The method of claim 3, 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 without the phase estimate of the channel estimate to produce the first block of secret bits when 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 when the gain estimate of the channel estimate is more than the second threshold.

5. The method of claim 4, 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.

6. 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 further comprises using the second public information.

7. The method of claim 6, wherein the second public information comprises a subset of the first public information.

8. The method of claim 7, wherein the second public information comprises one or more time instances where the second user selects to generate a second block of secret bits.

9. The method of claim 8, wherein the second user generates a second block of secret bits using a second channel estimate, wherein the second channel estimate comprises a second gain estimate and a second phase estimate.

10. The method of claim 8, 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.

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

receiving, by a receiver, a first public information from a first user, the first public information determined by;

selecting a set of one or more time instances from which the first user produces a first channel estimate, wherein selecting the 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 time instances corresponding to the selected set of channel estimates; and

setting an indication of the selected set of one or more time instances as the first public information;

estimating, by a processor, 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;

determining, by the processor, whether to use only the second gain estimate to generate a second block of secret bits, or to use both the second gain estimate and the second phase estimate to generate the second block of secret bits; and

generating, by the processor, the second block of secret bits using the first public information and the second gain estimate and the second phase estimate of the channel,

wherein the generating comprises using the second gain estimate without the second phase estimate to generate the second block of secret bits, when the second gain estimate is less than the first threshold, and

wherein the generating comprises using the second gain estimate and the second phase estimate to generate the second block of secret bits, when the second gain estimate is more than the second threshold, wherein the first threshold is lower than the second threshold.

12. The method of claim 11, wherein the second user produces a second public information using the second channel estimate, and transmits the second public information to the first user.

13. The method of claim 12, wherein the generating the second block of secret bits is using the second public information.

14. The method of claim 11, wherein the indication of the selected set of one or more time instances indicate when the second user performs the channel estimation.

15. The method of claim 13, wherein the generating a second block of secret bits comprises:

determining the first threshold and the second threshold; and

quantizing a set of channel estimates indicated by the second public information using 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.

16. The method of claim 15, wherein quantizing a set of channel estimates indicated by the second public information using 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 without the phase estimate of the channel estimate when 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 when the gain estimate of the channel estimate is more than the second threshold.

17. The method of claim 16, 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.

18. A first communications device comprising:

a non-transitory memory containing instructions; and

a processor coupled to the memory for executing the instructions, the instructions comprising;

channel estimate instructions for estimating a channel between the first communications device and a remote communications device;

threshold instructions for determining one or more thresholds using the channel estimate;

channel select instructions for;

selecting a set of one or more time instances from which the channel estimate unit produces the channel estimate, wherein the instructions for selecting the set of one or more time instances comprise instructions for;

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 a first threshold or all more than a second threshold, where M is a positive integer value; and

selecting time instances corresponding to the selected set of channel estimates; and

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

key generate instructions for;

generating secret bits using a gain of the channel estimate and a phase of the channel estimate;

determining whether to use only the gain of the channel estimate to generate the secret bits, or to use both the gain of the channel estimate and the phase of the channel estimate to generate the secret bits;

using the gain of the channel estimate without the phase of the channel estimate to generate the secret bits, when the gain of the channel estimate is less than the first threshold; and

using the gain of the channel estimate and the phase of the channel estimate to generate the secret bits, when the gain of the channel estimate is more than the second threshold, wherein the first threshold is lower than the second threshold.

19. The first communications device of claim 18, wherein the key generate instructions comprise instructions for generating the secret bits using a relationship between a gain of the channel estimate and the one or more thresholds.

20. The first communications device of claim 19, wherein the key generate unit comprises instructions comprise instructions for:

quantizing a phase of a channel estimate;

quantizing a gain of a channel estimate;

generating the secret bits using a codeword produced by the quantizing of the phase and/or gain of the channel estimate; and

comparing the gain of the channel estimate with the one or more thresholds and to generate a control signal using the comparison.

21. The first communications device of claim 18, wherein the non-transitory memory contains encrypt/decrypt unit instructions for encoding transmissions to the remote communications device with the secret bits.

22. The first communications device of claim 18, wherein the key generate instructions comprise instructions for selecting a group of phase quantization bins from a plurality of groups of phase quantization bins, mapping 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 selecting at least a portion of the codeword as a part of the secret bits.

23. A first device for secure communications, the first device comprising:

a non-transitory memory containing instructions; and

a processor coupled to the memory for executing the instructions, wherein the instructions comprise;

channel estimator instructions for estimating a channel between the first device and a second device, thereby producing a first channel estimate comprising a first gain estimate and a first phase estimate of the channel;

determining instructions for determining first public information by;

selecting a set of one or more time instances from which the first device produces the first channel estimate, wherein selecting the 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 time instances corresponding to the selected set of channel estimates; and

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

generator instructions for;

generating a first block of secret bits using the first channel estimate;

determining whether to use only the first gain estimate to generate the first block of secret bits, or to use both the first gain estimate and the first phase estimate to generate the first block of secret bits;

using the first gain estimate without the first phase estimate to generate the first block of secret bits, when the first gain estimate is less than the first threshold; and

using the first gain estimate and the first phase estimate to generate the first block of secret bits, when the first gain estimate is more than the second threshold, wherein the first threshold is lower than the second threshold; and

a transmitter for transmitting the first public information regarding the first channel estimate to the second device.

24. The first device of claim 23, wherein the determining instructions comprise instructions for determining the first public information by selecting a set of one or more time instances from which the first 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.

25. The first device of claim 24, wherein the determining instructions comprise instructions for determining 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.

26. The first device of claim 24, further comprising a receiver for receiving a second public information from the second device, and wherein the generator instructions comprise instructions for generating the first block of secret bits using the second public information.

27. A first device for secure communications, the first device comprising:

a receiver for receiving a first public information from a second device, the first public information determined by;

selecting a set of one or more time instances from which the second device produces a first channel estimate, wherein selecting the 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 time instances corresponding to the selected set of channel estimates; and

setting an indication of the selected set of one or more time instances as the first public information;

a non-transitory memory containing instructions; and

a processor coupled to the memory for executing the instructions, the instructions comprising;

channel estimator instructions for estimating a channel between the second device and the first device, thereby producing a second channel estimate comprising a second gain estimate and a second phase estimate of the channel; and

generator instructions for;

generating a second block of secret bits using the first public information and the second gain estimate and the second phase estimate of the channel;

determining whether to use only the second gain estimate to generate the second block of secret bits, or to use both the second gain estimate and the second phase estimate to generate the second block of secret bits;

using the second gain estimate without the second phase estimate to generate the second block of secret bits, when the second gain estimate is less than the first, threshold; and

using the second gain estimate and the second phase estimate to generate the second block of secret bits, when the second gain estimate is more than the second threshold, wherein the first threshold is lower than the second threshold.

28. The first device of claim 27, wherein the non-transitory memory contains information producer instructions for producing a second public information using the second channel estimate, the second public information to be transmitted to the second device.

29. The first device of claim 27, wherein the an indication of the set of one or more time instances indicates when the channel estimator performs the channel estimation.