Generation of perfectly secret keys in wireless communication networks

• US 8,238,551 B2
• Filed: 01/26/2006
• Issued: 08/07/2012
• Est. Priority Date: 01/27/2005
• Status: Expired due to Fees

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Reznik, Alexander, Kumoluyi, Akinlolu Oloruntosi, Zhang, Guodong, Chitrapu, Prabhakar R., Sternberg, Gregory S., Shah, Yogendra C., Briancon, Alain Charles Louis, Ye, Chunxuan
• Primary Examiner(s): Flynn, Nathan
• Assistant Examiner(s): Almamun, Abdullah
• Application Number:
  US11/339,958
• Publication Number:
  US 20070177729A1
• Time in Patent Office: 2,385 Days
• Field of Search: 380/21, 380/44, 380/201, 380/44.47, 380/270, 380/276, 380/277, 713/189, 713/200, 713/201, 455/11, 455/410, 714/790
• US Class Current: 380/44
• CPC Class Codes: H04K 1/00 Secret communication
• CPC Class Codes: H04L 2209/80 Wireless
• CPC Class Codes: H04L 25/0202 Channel estimation
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 9/0858 Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding
• CPC Class Codes: H04L 9/0875 based on channel impulse response [CIR]
• CPC Class Codes: H04L 9/12 Transmitting and receiving encryption devices synchronised or initially set up in a particular manner
• 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: Y04S 40/20 Information technology specific aspects, e.g. CAD, simulation, modelling, system security

Abstract

A method and apparatus is used for generating a perfectly random secret key between two or more transceivers in a wireless communication network. In a point-to-point system, both transceivers produce an estimate of the channel impulse response (CIR) based on the received radio signal. The CIR estimation is synchronized and may include error correction and detection. A long secret key of bits is generated from a digitized version of the CIR estimate, from which a perfectly secret encryption key is derived by privacy amplification.

Claims

1. A method comprising:

generating a plurality of channel impulse response (CIR) estimates at a wireless transmit/receive unit (WTRU) by estimating each of a plurality of radio signals received from a plurality of wireless transmit/receive units (WTRUs);

generating a plurality of secret keys, each of the plurality of secret keys based on one of the plurality of CIR estimates and associated with one of the plurality of WTRUs;

selecting a shared secret key by selecting a shortest length secret key from the plurality of secret keys; and

communicating the shared secret key to each WTRU in the plurality of WTRUs using a secret key from among the plurality of secret keys associated with each respective recipient WTRU.

2. The method of claim 1, further comprising generating a perfectly secret encryption key from the shared secret key, wherein the generating the perfectly secret encryption key comprises:

mapping the secret key according to a universal hash function which extracts entropy from the first CIR estimate and removes public bits.

3. The method of claim 1, further comprising generating a perfectly secret encryption key from the shared secret key, wherein the generating the perfectly secret encryption key comprises:

entropy encoding using a Burrows-Wheeler Transform.

4. The method of claim 1, further comprising generating a perfectly secret encryption key from the shared secret key, wherein the generating the perfectly secret encryption key comprises:

generating a non-systematic code for the secret key.

5. The method of claim 1, further comprising:

deriving syndrome bits a first WTRU from among the plurality of WTRUs; and

transmitting the syndrome bits to a second WTRU from among the plurality of WTRUs.

6. The method of claim 1, further comprising:

deriving a block error correcting code having parity bits for a first WTRU from among the plurality of WTRUs; and

transmitting the parity bits to a second WTRU from among the plurality of WTRUs.

7. The method of claim 1, further comprising:

selecting an error correction code from a family of codes based on a channel condition.

8. The method of claim 7, wherein the error correction code is differentiated using at least one of a puncturing pattern and a repetition pattern.

9. The method of claim 7, wherein the channel condition includes an interference level.

10. The method of claim 7, wherein the channel condition includes a Doppler spread.

11. The method of claim 7, wherein the channel condition includes a Doppler spread or a direction of travel or a combination of a Doppler spread and a direction of travel.

12. The method of claim 7, wherein the channel condition is measured based on a bit error rate or a block error rate.

13. The method of claim 1, further comprising:

deriving error detection bits;

appending the error detection bits to at least one CIR estimate from among the plurality of CIR estimates; and

encoding an error correction code including the error detection bits.

14. The method of claim 13, wherein the error detection code includes a plurality of cyclic redundancy check (CRC) bits.

15. The method of claim 1, wherein each of the plurality of radio signals comprises a frame.

16. The method of claim 1, further comprising:

performing a weak key analysis, such that the shared secret key is rejected based on extrinsic characteristics that affect secrecy according to predefined criteria.

17. The method of claim 16, where the predefined criteria includes a repetitive string within a defined period.

18. The method of claim 1, wherein the generating each of the plurality of CIR estimates comprises producing a plurality of CIR estimates for each radio signal of the plurality of radio signals, and generating each of the plurality of secret keys comprises continuously updating each of the plurality of secret keys by:

filtering the plurality of CIR estimates for each radio signal of the plurality of radio signals to produce a predicted set of values for each radio signal of the plurality of radio signals;

generating a difference vector between a current set of estimates for each radio signal of the plurality of radio signals and the predicted values for each radio signal of the plurality of radio signals; and

updating each of the plurality of secret keys using the respective generated difference vector.

19. The method of claim 18, further comprising:

generating at least one parity stream from each difference vector;

performing puncturing or repetition on the parity stream at a rate according to a target transmit rate.

20. The method of claim 19, further comprising:

adapting the puncturing rate or the repetition rate according to a channel condition.

21. The method of claim 20, wherein the channel condition comprises an interference level.

22. The method of claim 20, wherein the channel condition comprises a Doppler spread.

23. The method of claim 20, wherein the channel condition comprises one of a Doppler spread, a direction of travel, and a combination of a Doppler spread and a direction of travel.

24. The method of claim 20, wherein the channel conditions are measured based on at least one of a bit error rate and a block error rate.

25. The method of claim 1, wherein the generating a perfectly secret encryption key includes using a block for error correction of the secret key.

26. The method of claim 1, further comprising receiving from a first WTRU of the plurality of WTRUs a portion of a common key used by a subset of the plurality of WTRUs.

27. The method of claim 1, where the communicating comprises generating a tree graph of the plurality of other WTRUs.

28. A wireless transmit/receive unit (WTRU) comprising:

a channel estimator configured to produce a plurality of channel impulse response (CIR) estimates, each based on one of a plurality of radio signals received from a plurality of wireless transmit/receive units (WTRUs);

a post processor configured to;

generate a plurality of secret keys, each of the plurality of secret keys based on one of the plurality of CIR estimates and associated with one of the plurality of WTRUs, and

select a shared secret key by selecting a shortest length secret key from the plurality of secret keys; and

a transmitter configured to communicate the shared secret key to each WTRU in the plurality of WTRUs using a secret key from among the plurality of secret keys associated with each respective recipient WTRU.

29. The WTRU of claim 28, further comprising an encryption processor configured to generate a perfectly secret encryption key from the shared secret key, wherein the encryption processor is configured to map the shared secret key according to a universal hash function that extracts entropy from a CIR estimate and removes public bits.

30. The WTRU of claim 28, further comprising an encryption processor configured to generate a perfectly secret encryption key from the shared secret key, wherein the encryption processor includes an entropy encoder configured to perform a Burrows-Wheeler Transform.

31. The WTRU of claim 28, further comprising:

an error detection encoder configured to compute a plurality of cyclic redundancy check (CRC) bits according to an error detection code and to append the CRC bits to a CIR estimate from among the plurality of CIR estimates.

32. The WTRU of claim 28, further comprising an encryption processor configured to generate a perfectly secret encryption key from the shared secret key a non-systematic code for the shared secret key.

33. The WTRU of claim 28, further comprising:

a weak key analyzer configured to reject the shared secret key based on extrinsic characteristics that affect secrecy according to predefined criteria.

34. The WTRU of claim 28 further comprising:

a decoder configured to decode parity bits received from each of the plurality of WTRUs for error correction.