Robust watermarking for digital objects

• US 6,463,162 B1
• Filed: 09/30/1998
• Issued: 10/08/2002
• Est. Priority Date: 09/30/1998
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Vora, Poorvi L.
• Primary Examiner(s): Couso, Jose L.
• Application Number:
  US09/163,716
• Time in Patent Office: 1,469 Days
• Field of Search: 382/100, 382/232, 382/284, 395/135, 358/454, 358/448, 358/450, 358/142, 358/124, 380/4, 380/23, 380/25, 380/54, 283/6, 283/93, 283/94, 348/475, 235/494
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0057 Compression invariant watermarking
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: H04N 1/32154 Transform domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/3216 using Fourier transforms
• CPC Class Codes: H04N 1/32165 using cosine transforms
• CPC Class Codes: H04N 1/3217 using wavelet transforms
• CPC Class Codes: H04N 1/32176 using Walsh, Hadamard or Walsh-Hadamard transforms
• CPC Class Codes: H04N 1/32277 Compression
• CPC Class Codes: H04N 19/467 characterised by the embedded information being invisible, e.g. watermarking

Abstract

Method of embedding a watermark in a digital object. The watermark is used to perform argument modulation of a transform of the object. Watermark data is used in the argument of the transform to effectively shift around values in the transform domain.

Claims

1. A method comprising the steps of:

a) applying a transform to a digital object to generate a transformed digital object comprising a plurality of elements indexed by a first set of arguments;

b) modulating the first set of arguments to selectively replace elements at selected locations within the transformed digital object with other elements from other locations within the transformed digital object to generate a watermarked transformed digital object; and

c) performing an inverse transform of the watermarked transformed digital object to generate a watermarked digital object.

2. The method of claim 1 wherein the digital object is one of a still image, a digital audio stream, or a stream of digital images.

3. The method of claim 1 wherein the digital object includes an image processed in a selected color space having a plurality of elements, wherein the watermark is incorporated into at least one element of the color space.

4. A method comprising the steps of:

a) transforming a digital object from a first domain f(i_l, . . .i_n) to a second domain F(k_l, . . . k_n); and

b) modulating each argument of the transformed digital object to form a watermarked transformed digital object of the form G(k_i, . . . . k_n) wherein G(k_l, . . .k_n)=F(k₁+λ

₁, . . . k_n+λ

_n), wherein λ

_i=α

_i×

w_i(k_i, . . .k_n)−

γ

, wherein w_i(k_l, . . . .k_n) corresponds to the watermark for each argument, k_i.

5. The method of claim 4 further comprising the step of:

c) performing an inverse transform to generate the digital information incorporating the watermark in the first domain.

6. The method of claim 4 wherein w_i(k_l, . . .k_n)=w(k_l, . . .k_n) for 1≦

i≦

n.

7. The method of claim 4 wherein n=2.

8. The method of claim 4 wherein α

_i=α

for 1≦

i≦

n.

9. The method of claim 8 wherein α

is constant.

10. The method of claim 8 wherein α

is a function of F(k_l, . . .k_n).

11. The method of claim 8 wherein γ

_i=γ

for 1≦

i≦

n.

12. The method of claim 11 wherein γ

is constant.

13. The method of claim 11 wherein γ

is a function of F(k_l, . . . k_n).

14. The method of claim 4 wherein the transform is one of a Fourier, discrete Fourier (DFT), discrete cosine (DCT), discrete sine (DST), Walsh, Hadamard, Hartley, or Wavelet transform.

15. A computer storage medium having instructions stored therein for programming a computer to perform the method of claim 4.

16. The method of claim 4 further comprising the steps of:

c) quantizing the watermarked transformed digital object; and

d) compressing the quantized result.

17. A method of extracting a watermark embedded in a candidate digital object, comprising the steps of:

a) applying a transform to each of an original digital object and the candidate digital object;

b) modulating arguments of a selected one of the transformed original and candidate digital objects in accordance with modulation parameters; and

c) identifying a resulting set of modulation parameters resulting in a minimum difference between the modulated transformed digital object and the other transformed digital object, wherein the resulting set of modulation parameters identify the watermark.

18. The method of claim 17 wherein the modulation parameters are of the form α

×

w(k_l, . . . k_n)+γ

for each transform argument k_i, wherein w(k_l, . . . k_n) corresponds to the watermark.

19. A computer storage medium having instructions stored therein for programming a computer to perform the method of claim 17.

20. The method of claim 17 wherein the digital object is one of a still image, a digital audio stream, or a stream of digital images.