Watermark applied to one-dimensional data

• US 6,425,082 B1
• Filed: 07/19/2000
• Issued: 07/23/2002
• Est. Priority Date: 01/27/1998
• Status: Expired due to Term

• Current Assignee: KOWA Company Limited
• Original Assignee: KOWA Company Limited
• Inventors: Matsui, Kineo, Iwakiri, Munetoshi
• Primary Examiner(s): Barrón, Gilberto
• Assistant Examiner(s): Callahan, Paul E.
• Application Number:
  US09/619,022
• Time in Patent Office: 734 Days
• Field of Search: 380/207, 380/208, 380/237, 380/238, 713/176, 382/250, 382/283, 382/306
• US Class Current: 713/176
• CPC Class Codes: G10L 19/018 Audio watermarking, i.e. embedding inaudible data in the audio signal
• CPC Class Codes: G10L 21/00 Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility G10L19/00 takes precedence
• CPC Class Codes: G10L 25/00 Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 muting semiconductor-based amplifiers when some special characteristics of a signal are sensed by a speech detector, e.g. sensing when no signal is present, H03G3/34
• 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 20/00913 based on a spread spectrum technique
• CPC Class Codes: H04B 1/707 using direct sequence modulation

Abstract

In the process of embedding watermark information in one-dimensional source data, first spread one-dimensional data x(t) is generated by subjecting one-dimensional source data s(t) to spectrum-spreading operation using a PN sequence g(t). This first spread one-dimensional data x(t) then undergoes a modified discrete cosine transformation. A specific frequency component value of the MDCT coefficients is modulated to provide association with the watermark information. The modulated frequency component then undergoes inverse transformation to generate second spread one-dimensional data x′(t). Then, using the same PN sequence in the spreading, the second spread one-dimensional data is subjected to spectrum-despreading to produce digitally watermarked one-dimensional data in which watermark data has been embedded.

Claims

1. A method for embedding watermark information in one-dimensional source data, comprising the steps of:

(a) performing spectrum-spreading by an operation equivalent to multiplying the one-dimensional source data by a specific positive/negative value sequence that randomly assumes positive/negative values having a specific absolute value, thereby generating first spread one-dimensional data;

(b) subjecting the first spread one-dimensional data to orthogonal transformation;

(c) modulating a specific frequency component value of transform coefficients obtained through the orthogonal transformation to provide association with the watermark information;

(d) subjecting the modulated frequency component to inverse orthogonal transformation to generate second spread one-dimensional data; and

(e) performing spectrum-despreading on the second spread one-dimensional data using the specific positive/negative value sequence to generate digitally watermarked one-dimensional data in which the watermark information has been embedded.

2. A method for embedding a digital watermark according to claim 1, wherein the steps (a) and (e) each include a step of generating the specific positive/negative value sequence according to a specific frequency generation key.

3. A method for embedding a digital watermark according to claim 1, wherein the orthogonal transformation is modified discrete cosine transformation wherein each frame composed of 2M data (M is an integer equal to 2 or greater) in the first spread one-dimensional data is subjected to transformation using a predetermined window function;

and

the first spread one-dimensional data is divided into a plurality of frames in the modified discrete cosine transformation such that adjacent frames take locations mutually shifted by intervals of M data.

4. A method for embedding a digital watermark according to claim 3, wherein the specific frequency component associated with the watermark information is a frequency component value substantially equivalent to M/2.

5. A method for embedding a digital watermark according to claim 1, wherein the step (c) includes:

(i) quantizing the specific frequency component by a predetermined integer kd to generate a first quantized value;

(ii) associating the least significant bit of the first quantized value with the watermark information bit value through modulation to generate a second quantized value; and

(iii) multiplying the second quantized value by the predetermined integer kd to generate the modulated frequency component.

6. An apparatus for embedding a digital watermark in one-dimensional source data, comprising:

a spectrum-spreading section that performs spectrum-spreading by an operation equivalent to multiplying the one-dimensional source data by a specific positive/negative value sequence that randomly assumes positive/negative values having a specific absolute value, thereby generating first spread one-dimensional data;

an orthogonal transformation section that subjects the first spread one-dimensional data to orthogonal transformation;

an embedding section that modulates the specific frequency component value of transform coefficients obtained through the orthogonal transformation to provide association with the watermark information;

an inverse transformation section that subjects the modulated frequency component to inverse transformation to generate second spread one-dimensional data; and

a despreading section that performs spectrum-despreading on the second spread one-dimensional data using the specific positive/negative sequence to generate digitally watermarked one-dimensional data in which the watermark information has been embedded.

7. The apparatus for embedding a digital watermark according to claim 6, wherein the spectrum-spreading section includes a positive/negative sequence generator for generating the specific positive/negative sequence according to a specific frequency generation key.

8. The apparatus for embedding a digital watermark according to claim 6, wherein the orthogonal transformation section performs modified discrete cosine transformation using a predetermined window function on each frame composed of 2M data (M is an integer equal to 2 or greater) in the first spread one-dimensional data;

and

the first spread one-dimensional data is divided into a plurality of frames in the modified discrete cosine transformation such that adjacent frames take locations mutually shifted by intervals of M data.

9. The apparatus for embedding a digital watermark according to claim 8, wherein the specific frequency component associated with the watermark information is a frequency component value substantially equivalent to M/2.

10. The apparatus for embedding digital watermark according to claim 6, wherein

the embedding section comprises a quantizing section that quantizes the specific frequency component with a scale key kd to generate a first quantized value;

a bit modulating section that modulates the least significant bit of the first quantized value to provide association with a bit value of the watermark information to generate a second quantized value; and

an inverse quantizing section that generates the modulated frequency component by multiplying the second quantized value by the predetermined integer kd.

11. A computer-readable storage medium for storing a computer program for embedding watermark information in one-dimensional source data, the computer-readable storage medium storing a computer program for causing a computer to execute:

a spectrum-spreading function for performing spectrum-spreading by an operation equivalent to multiplying the one-dimensional source data by a specific positive/negative value sequence that randomly assumes positive/negative values having a specific absolute value, thereby generating first spread one-dimensional data;

an orthogonal transformation function for subjecting the first spread one-dimensional data to orthogonal transformation;

an embedding function for modulating the specific frequency component value of transform coefficients obtained through the orthogonal transformation to provide association with the watermark information;

an inverse transformation function for subjecting the modulated frequency component to inverse orthogonal transformation to generate second spread one-dimensional data; and

a despreading function for performing spectrum-despreading on the second spread one-dimensional data using the specific positive/negative sequence to generate digitally watermarked one-dimensional data in which the watermark information has been embedded.

12. A computer-readable storage medium storing digitally watermarked one-dimensional data containing embedded watermark information, the digitally watermarked one-dimensional data being generated by:

spectrum-spreading by an operation equivalent to multiplying the one-dimensional source data by a specific positive/negative value sequence that randomly assumes positive/negative values having a specific absolute value, thereby generating first spread one-dimensional data;

subjecting the first spread one-dimensional data to orthogonal transformation;

modulating the specific frequency component value of transform coefficients obtained through the orthogonal transformation to provide association with the watermark information;

subjecting the modulated frequency component to inverse transformation to generate second spread one-dimensional data; and

spectrum-despreading the second spread one-dimensional data using the specific positive/negative sequence to generate digitally watermarked one-dimensional data in which the watermark information has been embedded.

13. A method for extracting watermark information from digitally watermarked one-dimensional data in which the watermark information has been embedded, comprising the steps of:

(a) performing spectrum-spreading by an operation equivalent to multiplying the digitally watermarked one-dimensional data by a specific positive/negative value sequence that randomly assumes positive/negative values having a specific absolute value, thereby generating first spread digitally watermarked one-dimensional data;

(b) subjecting the first spread digitally watermarked one-dimensional data to orthogonal transformation; and

(c) extracting the watermark information associated with the specific frequency component value from the frequency component of the transformation coefficients obtained by the orthogonal transformation.

14. An apparatus for extracting watermark information from digitally watermarked one-dimensional data in which the watermark information has been embedded, comprising:

a spectrum-spreading section that performs spectrum-spreading by an operation equivalent to multiplying the digitally watermarked one-dimensional data by a specific positive/negative value sequence that randomly assumes positive/negative values having a specific absolute value, thereby generating first spread digitally watermarked one-dimensional data;

an orthogonal transformation section that subjects the first spread digitally watermarked one-dimensional data to orthogonal transformation; and

a decoder that extracts the watermark information associated with the specific frequency component value from the frequency component of the transformation coefficients obtained by the orthogonal transformation.

15. A computer-readable storage medium for storing a computer program for extracting watermark information from digitally watermarked one-dimensional data in which the watermark information has been embedded, the computer-readable storage medium storing a computer program for causing a computer to execute:

a spectrum-spreading function for performing spectrum-spreading by an operation equivalent to multiplying the digitally watermarked one-dimensional data by a specific positive/negative value sequence that randomly assumes positive/negative values having a specific absolute value, thereby generating first spread digitally watermarked one-dimensional data;

an orthogonal transformation function for subjecting the first spread digitally watermarked one-dimensional data to orthogonal transformation; and

a decoding function for extracting the watermark information associated with the specific frequency component value from the frequency component of the transformation coefficients obtained by the orthogonal transformation.

16. A computer-readable storage medium storing digitally watermarked one-dimensional data containing embedded watermark information, the watermark information being able to be extracted by:

performing spectrum-spreading by an operation equivalent to multiplying the digitally watermarked one-dimensional data by a specific positive/negative value sequence that randomly assumes positive/negative values having a specific absolute value, thereby generating first spread digitally watermarked one-dimensional data;

subjecting the first spread digitally watermarked one-dimensional data to orthogonal transformation; and

extracting the watermark information associated with the specific frequency component value from the frequency component of the transformation coefficients obtained by the orthogonal transformation.