Steganographic encoding and decoding of auxiliary codes in media signals

• US 6,944,298 B1
• Filed: 05/31/2000
• Issued: 09/13/2005
• Est. Priority Date: 11/18/1993
• Status: Expired due to Fees

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimare Corporation
• Inventors: Rhoads, Geoffrey B.
• Primary Examiner(s): Caldwell, Andrew
• Assistant Examiner(s): Callahan, Paul E.
• Application Number:
  US09/585,726
• Time in Patent Office: 1,931 Days
• Field of Search: 380/202, 380/242, 705/57, 725/31, 382/100, 382/232, 714/786, 714/794, 714/795, 713/176
• US Class Current: 380/205
• CPC Class Codes: G06Q 20/341 Active cards, i.e. cards including their own processing means, e.g. including an IC or chip
• CPC Class Codes: G06Q 20/40145 Biometric identity checks
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• CPC Class Codes: G07C 9/253 visually
• CPC Class Codes: G07D 7/0032 using holograms
• CPC Class Codes: G07D 7/004 using digital security elements, e.g. information coded on a magnetic thread or strip
• CPC Class Codes: G07F 17/16 for devices exhibiting advertisements, announcements, pictures or the like
• CPC Class Codes: G07F 7/08 by coded identity card or credit card or other personal identification means without personal verification means G07F7/02
• CPC Class Codes: G07F 7/086 by passive credit-cards adapted therefor, e.g. constructive particularities to avoid counterfeiting, e.g. by inclusion of a physical or chemical security-layer for security documents G07D7/00; for the reading of record-carriers in general G06K7/00; for the design of coded credit-cards G06K19/10
• CPC Class Codes: G07F 7/1008 Active credit-cards provided with means to personalise their use, e.g. with PIN-introduction/comparison system
• CPC Class Codes: G07F 7/1016 Devices or methods for securing the PIN and other transaction-data, e.g. by encryption arrangements for secret communication, see H04L9/00
• CPC Class Codes: G07F 7/12 Card verification
• CPC Class Codes: G10L 19/018 Audio watermarking, i.e. embedding inaudible data in the audio signal
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/00094 involving measures which result in a restriction to authorised record carriers
• CPC Class Codes: G11B 20/00166 involving measures which result in a restriction to authorised contents recorded on or reproduced from a record carrier, e.g. music or software
• CPC Class Codes: G11B 20/0021 involving encryption or decryption of contents recorded on or reproduced from a record carrier
• CPC Class Codes: G11B 20/00884 involving a watermark, i.e. a barely perceptible transformation of the original data which can nevertheless be recognised by an algorithm
• CPC Class Codes: G11B 20/00891 : embedded in audio data
• CPC Class Codes: H04B 1/665 : using psychoacoustic properties of the ear, e.g. masking effect
• CPC Class Codes: H04N 1/00005 : relating to image data
• CPC Class Codes: H04N 1/00037 : Detecting, i.e. determining the occurrence of a predetermined state H04N1/00031 takes precedence
• CPC Class Codes: H04N 1/00079 : remotely
• CPC Class Codes: H04N 1/32122 : in a separate device, e.g. in a memory or on a display separate from image data
• CPC Class Codes: H04N 1/32144 : embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
• CPC Class Codes: H04N 1/32208 : involving changing the magnitude of selected pixels, e.g. overlay of information or super-imposition H04N1/32219, H04N1/32224 take precedence
• CPC Class Codes: H04N 1/32251 : in multilevel data, e.g. greyscale or continuous tone data
• CPC Class Codes: H04N 1/32288 : Multiple embedding, e.g. cocktail embedding, or redundant embedding, e.g. repeating the additional information at a plurality of locations in the image
• CPC Class Codes: H04N 2005/91321 : the copy protection signal being a copy protection control signal, e.g. a record inhibit signal
• CPC Class Codes: H04N 2005/91335 : the copy protection signal being a watermark
• CPC Class Codes: H04N 2201/3205 : of identification information, e.g. name or ID code H04N2201/3209 takes precedence
• CPC Class Codes: H04N 2201/3207 : of an address
• CPC Class Codes: H04N 2201/3226 : of identification information or the like, e.g. ID code, index, title, part of an image, reduced-size image
• CPC Class Codes: H04N 2201/3233 : of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/327 : which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 2201/3271 : Printing or stamping
• CPC Class Codes: H04N 2201/328 : Processing of the additional information
• CPC Class Codes: H04N 5/913 : for scrambling ; for copy protection

Abstract

One aspect of the invention is a method of decoding an auxiliary code embedded in an audio signal. The method performs a statistical decoding of a multibit auxiliary code embedded in an audio signal. The auxiliary code has been repetitively embedded in the audio signal. The method decodes code values of the auxiliary code from two or more different portions of the audio signal, each having the multibit auxiliary code. It then uses the code values decoded from two or more different portions to determine statistically the code values of the auxiliary code. Another aspect of the invention is another method of decoding an auxiliary code embedded in an audio signal. The method receives an audio signal suspected of being embedded with an auxiliary code. It evaluates a statistical feature of a portion of the audio signal to decode code values of the auxiliary code from the audio signal. It then determines a code value in the auxiliary code based on the statistical feature. The statistical feature may comprise, for example, the power of the audio signal. The statistical feature may be analyzed over different portions of the audio signal to decode two or more values of the auxiliary code.

Claims

1. A method of decoding an auxiliary code embedded in an audio signal, the method comprising:

performing statistical decoding of a multibit auxiliary code embedded in an audio signal, where the auxiliary code has been repetitively embedded in the audio signal;

decoding code values of the auxiliary code from two or more different portions of the audio signal, each having the multibit auxiliary code;

wherein statistical features of portions of the audio signal have been modified according to statistical features associated with the code values to embed the code values in the audio signal;

using the code values decoded from the two or more different portions of the audio signal to determine statistically the code values of the auxiliary code.

2. The method of claim 1 wherein bit values for code bits are decoded from each portion, and values decoded for the same code bits from different portions are used to statistically derive a bit value for each of the code bits.

5. The method of claim 1 wherein the auxiliary code is embedded in a digitized form of the audio signal by changing sample values of the digitized audio signal in the time domain.

6. The method of claim 5, wherein signal scaling with which the auxiliary code is embedded in the audio signal varies depending on sample values of the digitized audio signal.

7. The method of claim 1 wherein the auxiliary code is recoverable from a portion of the audio signal, and confidence with which the auxiliary code is accurately recovered increases with the number of different audio portions from which the auxiliary code is decoded.

8. The method of claim 1 wherein the auxiliary code comprises a code that enables or disables recording capabilities.

9. The method of claim 1 wherein the auxiliary code comprises a copyright identification code.

10. The method of claim 1 wherein the auxiliary code comprises a code used to monitor a broadcast of the audio signal.

11. The method of claim 1 wherein the auxiliary code comprises a code that triggers transmission of information about the audio signal from a decoding device to a service provider.

12. The method of claim 1 wherein the auxiliary code is used to generate a report about use of the audio signal.

3. A method of decoding an auxiliary code embedded in an audio signal, the method comprising:

performing statistical decoding of a multibit auxiliary code embedded in an audio signal, where the auxiliary code has been repetitively embedded in the audio signal;

decoding code values of the auxiliary code from two or more different portions of the audio signal, each having the multibit auxiliary code;

using the code values decoded from the two or more different portions of the audio signal to determine statistically the code values of the auxiliary code;

wherein a statistical feature of the audio signal is analyzed to decode the code values of the auxiliary code and wherein the statistical feature of the audio signal comprises entropy.

4. A method of decoding an auxiliary code embedded in an audio signal, the method comprising:

performing statistical decoding of a multibit auxiliary code embedded in an audio signal, where the auxiliary code has been repetitively embedded in the audio signal;

decoding code values of the auxiliary code from two or more different portions of the audio signal, each having the multibit auxiliary code;

using the code values decoded from the two or more different portions of the audio signal to determine statistically the code values of the auxiliary code;

wherein a statistical feature of the audio signal is analyzed to decode the code values of the auxiliary code and wherein the statistical feature of the audio signal comprises power.

13. A computer readable medium on which is stored software for performing a method of decoding an auxiliary code embedded in an audio signal, the method comprising:

performing statistical decoding of a multibit auxiliary code embedded in an audio signal, where the auxiliary code has been repetitively embedded in the audio signal;

decoding code values of the auxiliary code from two or more different portions of the audio signal, each having the multibit auxiliary code;

wherein statistical features of portions of the audio signal have been modified according to statistical features associated with the code values to embed the code values in the audio signal;

using the code values decoded from the two or more different portions of the audio signal to determine statistically the code values of the auxiliary code.

14. A method of decoding an auxiliary code embedded in an audio signal, the method comprising:

receiving an audio signal suspected of being embedded with an auxiliary code;

evaluating a statistical feature of a portion of the audio signal to decode code values of the auxiliary code from the audio signal; and

determining a code value in the auxiliary code based on the statistical feature;

wherein the statistical feature comprises power of the audio signal.

15. A method of steganographically encoding a set of source data with a set of auxiliary data, each of said sets of data comprising a plurality of elements, the method including:

(a) providing a carrier signal;

(b) processing elements of the carrier signal in accordance with a corresponding element of the set of auxiliary data to produce a processed datum, including scaling the processed datum as a function of the source data in a perceptual domain in which the source data is perceived by humans so as to make the processed datum adaptive to the source data in the perceptual domain;

(c) combining the processed datum with elements of said set of source data to produce an encoded datum, said combining including performing an addition operation between the processed data and said elements of source data;

(d) repeating steps (b) and (c) for other elements of the sets of auxiliary data and source data, thereby producing a set of encoded data;

including modulating a statistical characteristic of samples of the source data such that the resulting encoded source data has a statistical characteristic corresponding to a value of the auxiliary data element being encoded, and the auxiliary data element is decodable by measuring the statistical characteristic for elements of the encoded source data.

16. The method of claim 15 wherein the auxiliary data elements are decodable by performing a statistical analysis to determine a value of the statistical characteristic of a set of samples of the encoded source data, and based on the value of the statistical characteristic, determining a value of the encoded auxiliary data element.

17. The method of claim 16 including modulating a statistical characteristic of time domain samples of an audio signal by adding the processed datum with the source data in a time domain.

18. A method of steganographically encoding a set of source data with a set of auxiliary data, each of said sets of data comprising a plurality of elements, the method including:

(a) providing a carrier signal;

(b) processing elements of the carrier signal in accordance with a corresponding element of the set of auxiliary data to produce a processed datum, including scaling the processed datum as a function of the source data in a perceptual domain in which the source data is perceived by humans so as to make the processed datum adaptive to the source data in the perceptual domain;

(c) combining the processed datum with elements of said set of source data to produce an encoded datum, said combining including performing an addition operation between the processed data and said elements of source data;

(d) repeating steps (b) and (c) for other elements of the sets of auxiliary data and source data, thereby producing a set of encoded data;

including modulating statistical characteristics of time domain samples of the source signal such that the auxiliary data is decoded by computing the statistical characteristics of the samples of the encoded source signal.

19. The method of claim 18 wherein the statistical characteristics are modulated by adding the carrier signal that has been modulated with the auxiliary data.

20. A method of steganographically encoding a set of source data with a set of auxiliary data, each of said sets of data comprising a plurality of elements, the method including:

providing a carrier signal;

processing elements of the carrier signal in accordance with corresponding elements of the set of auxiliary data to produce processed data sets;

combining the processed data sets with elements of said set of source data to produce encoded source data, including modulating a statistical characteristic of samples of the source data such that the resulting encoded source data has a statistical characteristic corresponding to a value of the auxiliary data element being encoded, and the auxiliary data element is decodable by measuring the statistical characteristic for elements of the encoded source data.

21. The method of claim 20 wherein the auxiliary data elements are decodable by performing a statistical analysis to determine a value of the statistical characteristic of a set of samples of the encoded source data, and based on the value of the statistical characteristic, determining a value of the encoded auxiliary data element.

22. The method of claim 20, includes modulating a statistical characteristic of time domain samples of an audio signal by adding the processed data sets with the source data in a time domain.

25. The method of claim 20 including:

repeating instances of the auxiliary data throughout the source data, and with each instance, varying the carrier signal.

23. A computer readable medium on which is stored instructions for performing a method of steganographically encoding a set of source data with a set of auxiliary data, each of said sets of data comprising a plurality of elements, the method including:

providing a carrier signal;

processing elements of the carrier signal in accordance with corresponding elements of the set of auxiliary data to produce processed data sets;

combining the processed data sets with elements of said set of source data to produce encoded source data, including modulating a statistical characteristic of samples of the source data such that the resulting encoded source data has a statistical characteristic corresponding to a value of the auxiliary data element being encoded, and the auxiliary data element is decodable by measuring the statistical characteristic for elements of the encoded source data.

24. A steganographic decoder operable to decode the encoded source data which has been encoded according to a method of steganographically encoding a set of source data with a set of auxiliary data, each of said sets of data comprising a plurality of elements, the method including:

providing a carrier signal;

processing elements of the carrier signal in accordance with corresponding elements of the set of auxiliary data to produce processed data sets;

combining the processed data sets with elements of said set of source data to produce encoded source data, including modulating a statistical characteristic of samples of the source data such that the resulting encoded source data has a statistical characteristic corresponding to a value of the auxiliary data element being encoded, and the auxiliary data element is decodable by measuring the statistical characteristic for elements of the encoded source data.

26. A method of steganographically encoding a set of source data with a set of auxiliary data, each of said sets of data comprising a plurality of elements, the method including:

providing a transformation between auxiliary data elements and a code signal;

processing elements of the auxiliary data in accordance with the transformation to produce processed data sets;

combining the processed data sets with elements of said set of source data to produce encoded source data, including modulating a statistical characteristic of samples of the source data such that the resulting encoded source data has a statistical characteristic corresponding to a value of the auxiliary data element being encoded, and the auxiliary data element is decodable by measuring the statistical characteristic for elements of the encoded source data.

27. The method of claim 26 including:

repeating instances of the auxiliary data throughout the source data, and with each instance, varying the transformation.