Asymmetric spread-spectrum watermarking systems and methods of use

• US 20020191809A1
• Filed: 02/27/2001
• Published: 12/19/2002
• Est. Priority Date: 02/27/2001
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Kirovski, Darko, Yacobi, Yacov
• Granted Patent: US 6,891,958 B2
• Time in Patent Office: Days
• US Class Current: 382/100
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• CPC Class Codes: H04K 1/00 Secret communication
• CPC Class Codes: H04L 2209/26 Testing cryptographic entity, e.g. testing integrity of encryption key or encryption algorithm
• CPC Class Codes: H04L 2209/608 Watermarking
• CPC Class Codes: H04L 9/30 Public key, i.e. encryption algorithm being computationally infeasible to invert or user's encryption keys not requiring secrecy

Abstract

Described herein is an audio watermarking technology for detecting watermarks in audio signals, such as a music clip. The watermark identifies the content producer, providing a signature that is embedded in the audio signal and cannot be removed. The watermark is designed to survive all typical kinds of processing and all types of malicious attacks that attempt to remove or modify the watermark from the signal. The implementations of the watermark detecting system, described herein, support quick, efficient, and accurate detection of watermarks by the specifically designed watermark detecting system. In one described implementation, a watermark detecting system employs an improved normalized covariance test to determine the presence of a watermark using less expensive materials (hardware), quicker calculations, and a more accurate test (than the original correlation test). In other described implementations, a watermark detecting system employs a cepstrum filter and dynamic processing to minimize the affect of the “noise” in the watermarked signal. The “noise” is the original content of the signal before such signal was watermarked. In still another described implementation, a watermark detecting system employs a mechanism for random detection threshold so that the act of watermark detection does not provide decipherable clues to a digital pirate as to the value or location of the embedded watermark.

Claims

1. A method, comprising:

combining a private key watermark signal with a watermark carrier signal to create a public key watermark signal;

combining the private key watermark signal with a content sequence to create a watermarked content sequence; and

wherein it can be determined if an input content sequence contains the private key watermark signal by correlating the input content sequence with the public key watermark signal.

2. The method as recited in claim 1, further comprising generating the private key watermark signal.

3. The method as recited in claim 1, wherein the watermark carrier signal further comprises a uniformly distributed signal having a variance great enough to hide the private key watermark signal.

4. The method as recited in claim 1, wherein:

the private key watermark signal has an amplitude; and

the watermark carrier signal further comprises a signal exhibiting a zero-mean Gaussian distribution having a standard deviation that is greater than the amplitude of the private key watermark signal.

5. The method as recited in claim 4, wherein the standard deviation of the watermark carrier signal is larger than the standard deviation of the private watermark signal such that a significant portion of the private key watermark signal cannot be determined from analyzing the public key watermark signal..

6. The method as recited in claim 5, wherein the standard deviation of the watermark carrier signal is from two and one-half times to five times the amplitude of the private key watermark signal.

7. The method as recited in claim 1, wherein the combining a private key watermark signal with a watermark carrier signal further comprises performing a linear point-to-point addition of the private key watermark signal and the watermark carrier signal.

8. The method as recited in claim 1, wherein the combining the private key watermark signal with a content sequence further comprises performing a linear point-to-point addition of the private key watermark signal and the content sequence.

9. The method as recited in claim 1, wherein the content sequence is an audio signal.

10. The method as recited in claim 1, wherein the content sequence is a video signal.

11. The method as recited in claim 1, wherein the content sequence is a digital image.

12. The method as recited in claim 1, wherein the content sequence is multimedia data.

13. The method as recited in claim 1, wherein the carrier signal is a pseudo-randomly generated signal.

15. The method as recited in claim 14, wherein the determining further comprises determining that the content sequence contains the private key watermark signal if the result of the correlation equals zero.

16. The method as recited in claim 14, wherein:

the content sequence has an amplitude ranging from +1 to −

1; and

the determining further comprises determining that the content sequence contains the private key watermark signal if the result of the correlation is less than one-half.

17. The method as recited in claim 14, wherein:

the content sequence has an amplitude; and

the determining further comprises determining that the content sequence does not contain the private key watermark signal if the result of the correlation equals the square of the cardinality of the amplitude of the content sequence.

18. The method as recited in claim 14, wherein:

the content sequence has an amplitude ranging from +1 to −

1; and

the determining further comprises determining that the content sequence does not contain the private key watermark signal if the result of the correlation equals 1.

19. The method as recited in claim 14, wherein:

the content sequence has an amplitude ranging from +1 to −

1; and

the determining further comprises determining that the content sequence does not contain the private key watermark signal if the result of the correlation is greater than one-half.

20. The method as recited in claim 14, wherein the content sequence is an audio signal.

21. The method as recited in claim 14, wherein the content sequence is a video signal.

22. The method as recited in claim 14, wherein the content sequence is a digital image.

24. The system as recited in claim 23, wherein the private key watermark unit is configured to store the private key watermark, which is accepted a priori.

25. The system as recited in claim 23, wherein the private key watermark unit is configured to generate the private key watermark.

26. The system as recited in claim 23, wherein the private key watermark unit is configured to generate the private key watermark from a secret key and a pseudo-random number generator.

27. The system as recited in claim 23, wherein:

the private key watermark signal has an amplitude; and

the watermark carrier signal further comprises a signal that exhibits a zero-mean Gaussian distribution having a standard deviation that is greater than the amplitude of the private key watermark signal.

28. The system as recited in claim 23, wherein the standard deviation of the watermark carrier signal is from two and one-half times to five times the amplitude of the private key watermark signal.

29. The system as recited in claim 23, wherein the content sequence further comprises a signal that exhibits a zero-mean Gaussian distribution having a standard deviation that is greater than the standard deviation of the watermark carrier signal.

30. The system as recited in claim 23, wherein the public key watermark signal generation unit is further configured to generate a public key watermark by linear point-to-point addition of the private key watermark signal and the watermark carrier signal.

31. The system as recited in claim 23, wherein the content sequence is an audio signal.

32. The system as recited in claim 23, wherein the content sequence is a video signal.

33. The system as recited in claim 23, wherein the content sequence is a digital image.

35. The system as recited in claim 34, wherein the determining further comprises determining that the content sequence contains the private key watermark signal if the correlation result approaches zero.

36. The system as recited in claim 34, wherein:

the content sequence has an amplitude; and

the determining further comprises determining that the content sequence does not contain the private key watermark signal if the correlation result approaches the cardinality of the amplitude of the content sequence.

37. The system as recited in claim 34, wherein:

the content sequence has an amplitude ranging from +1 to −

1; and

the determining further comprises determining that the content sequence contains the private key watermark signal if the result of the correlation is less than one-half.

38. The system as recited in claim 34, wherein:

the content sequence has an amplitude ranging from +1 to −

1; and

the determining further comprises determining that the content sequence does not contain the private key watermark signal if the result of the correlation is greater than one-half.

39. The system as recited in claim 34, wherein the content sequence is an audio signal.

40. The system as recited in claim 34, wherein the content sequence is a video signal.

41. The system as recited in claim 34, wherein the content sequence is a digital image.

14. A method for detecting a private key watermark signal in a content sequence using a public key watermark signal, comprising:

correlating the content sequence with the public key watermark signal;

determining if the content sequence contains the private key watermark signal based on the results of the correlation; and

wherein the public key watermark signal is a carrier signal containing the private key watermark signal.

23. A system for incorporating a private key watermark signal into a content sequence, comprising:

a processor;

memory;

a private key watermark unit;

a public key watermark signal generation unit configured to generate a public key watermark by incorporating the private key watermark signal into a watermark carrier signal;

a watermarking unit configured to incorporate the private key watermark signal into a content sequence; and

wherein it can be determined if the content sequence contains the private key watermark signal by correlating the content sequence with the public key watermark signal.

34. A system for determining whether a content sequence contains a private key watermark signal, comprising:

correlating the content sequence with a public key watermark signal;

determining whether the content sequence contains the private key watermark signal based on the results of the correlation; and

wherein the public key watermark is a carrier signal that contains the private key watermark.

42. One or more computer-readable media containing computer-executable instructions that, when executed on a computer, perform the following steps:

creating a public key watermark signal by incorporating a private key watermark signal into a watermark carrier signal;

watermarking a content sequence by incorporating the private key watermark signal into a the content sequence; and

wherein the private key watermark signal can be detected in the content sequence by correlating the public key watermark signal with the content sequence.

43. The one or more computer-readable media as recited in claim 42, further comprising computer-executable instructions that, when executed on a computer, generate the private key watermark signal.

44. The one or more computer-readable media as recited in claim 42, wherein:

the private key watermark signal has an amplitude; and

the watermark carrier signal further comprises a signal having a zero-mean Gaussian distribution with a standard deviation that is greater than the amplitude of the private key watermark signal.

45. The one or more computer-readable media as recited in claim 42, wherein the standard deviation of the watermark carrier signal is from two and one-half times to five time the amplitude of the private key watermark signal.

46. The one or more computer-readable media as recited in claim 42, wherein the content sequence further comprises a signal that exhibits a zero-mean Gaussian distribution having a standard deviation that is greater than the standard deviation of the watermark carrier signal.

47. The one or more computer-readable media as recited in claim 42, wherein the creating the public key watermark signal further comprises performing linear point-to-point addition with the private key watermark signal and the watermark carrier signal to create the public key watermark signal.

48. The one or more computer-readable media as recited in claim 42, wherein the watermarking further comprises creating a watermarked content sequence by linear point-to-point addition of the private key watermark signal and the content sequence.

49. The one or more computer-readable media as recited in claim 42, wherein the content sequence is an audio signal.

50. The one or more computer-readable media as recited in claim 42, wherein the content sequence is a video signal.

51. The one or more computer-readable media as recited in claim 42, wherein the content sequence is a digital image.

52. The one or more computer-readable media as recited in claim 42, wherein the content sequence is multimedia data.