Apparatus for and method of embedding and extracting digital information and medium having program for carrying out the method recorded thereon

• US 6,477,276 B1
• Filed: 11/05/1998
• Issued: 11/05/2002
• Est. Priority Date: 11/07/1997
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Ojima, Shuichi, Inoue, Hisashi, Iwasaki, Shiro, Katsura, Takashi, Shimazu, Mikio, Hatae, Eiichi, Miyazaki, Akio
• Primary Examiner(s): Johns, Andrew W.
• Assistant Examiner(s): Dang, Duy M.
• Application Number:
  US09/186,375
• Time in Patent Office: 1,461 Days
• Field of Search: 382/232, 382/203, 382/276, 382/279, 382/284, 382/100, 382/251, 380/40, 380/41, 380/51, 380/54, 375/240
• US Class Current: 382/232
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: G06T 2201/0061 Embedding of the watermark in each block of the image, e.g. segmented watermarking
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• 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 1/32187 with selective or adaptive application of the additional information, e.g. in selected frequency coefficients
• CPC Class Codes: H04N 1/32277 Compression
• CPC Class Codes: H04N 19/645 by grouping of coefficients into blocks after the transform
• 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

Abstract

An apparatus for embedding information in a signal includes a band dividing device, a block divider, a quantization portion, a signal replacement portion, a mean difference addition portion, a mean calculation portion, and a band synthesis portion. The band dividing device divides the signal into transform coefficients over a plurality of frequency bands. The block divider divides one frequency band into a plurality of blocks in accordance with a previously determined block size. The quantization portion calculates for each block, a mean value M of the transform coefficients in the block, and subjects the mean value M to linear quantization, using a previously determined quantization step-size Q to calculate a quantization value. The signal replacement portion replaces the quantization value for each block, on the basis of the quantization value and the value of the information to be embedded. The mean difference addition portion subjects the replaced quantization value, for each block, to inverse linear quantization using the quantization step-size Q to calculate a mean value M′, and adds a difference DM between the mean value M′ and the mean value M to all the transform coefficients in the block. The mean calculation portion calculates a mean value LM of the transform coefficients in the frequency band after the addition of the difference DM. The band synthesis portion reconstructs a signal in which the information has been embedded using the frequency band after the addition of the difference DM and the other frequency bands.

Claims

1. A digital information embedding apparatus for embedding inherent digital information in a digital image signal, comprising:

band division means for dividing said digital image signal into transform coefficients over a plurality of frequency bands using either a discrete wavelet transform or sub-band division;

block division means for dividing the lowest frequency band out of said plurality of frequency bands obtained by the division into a plurality of blocks in accordance with a previously determined block size;

quantization means for calculating a mean value M of the transform coefficients for each of said blocks, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q, wherein Q is an integer of not less than one, to calculate a quantization value;

signal replacement means for replacing the quantization value, for each of said blocks, and on the basis of said quantization value and the value of said digital information to be embedded which correspond to the block;

mean difference addition means for subjecting said replaced quantization value, for each of said blocks, to inverse linear quantization using said quantization step-size Q to calculate a mean value M′

, and for adding a difference DM, wherein DM=M′

−

M, between the mean value M′ and

said mean value M to all the transform coefficients in each block;

mean calculation means for calculating a mean value LM of the transform coefficients in the lowest frequency band after the addition of said difference DM; and

band synthesis means for reconstructing a digital image signal in which said digital information has been embedded using the lowest frequency band after the addition of said difference DM and the other frequency bands.

2. The digital information embedding apparatus according to claim 1, wherein said signal replacement means replaces the quantization value with an odd value closest to the value of M/Q when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of M/Q when each of bits composing said digital information takes a logical value 0.

3. A digital information embedding method of embedding inherent digital information in a digital image signal, comprising the steps of:

dividing said digital image signal into transform coefficients over a plurality of frequency bands using either a discrete wavelet transform or sub-band division;

dividing the lowest frequency band out of said plurality of frequency bands obtained by the division into a plurality of blocks in accordance with a previously determined block size;

calculating, for each of said blocks, a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q, wherein Q is an integer of not less than one, to calculate a quantization value;

replacing, for each of said blocks, and on the basis of said quantization value and the value of said digital information to be embedded which correspond to the block, the quantization value;

subjecting for each of said blocks said replaced quantization value to inverse linear quantization using said quantization step-size Q to calculate a mean value M′

, and adding a difference DM, wherein DM=M′

−

M, between the mean value M′ and

said mean value M to all the transform coefficients in the block;

calculating a mean value LM of the transform coefficients in the lowest frequency band after the addition of said difference DM; and

reconstructing a digital image signal in which said digital information has been embedded using the lowest frequency band after the addition of said difference DM and the other frequency bands.

4. The digital information embedding method according to claim 3, wherein said step of replacing the quantization value replaces the quantization value with an odd value closest to the value of M/Q when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of M/Q when each of bits composing said digital information a logical value 0.

5. A recording medium having a program executed in a computer recorded thereon, the program realizing on said computer an operational environment comprising the steps of:

dividing a digital image signal into a plurality of frequency bands to obtain transform coefficients using either a discrete wavelet transform or sub-band division;

dividing the lowest frequency band out of said plurality of frequency bands obtained by the division into a plurality of blocks in accordance with a previously determined block size;

calculating for each of said blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q, wherein Q is an integer of not less than one, to calculate a quantization value;

replacing, for each of said blocks, and on the basis of said quantization value and the value of said digital information to be embedded which correspond to the block, the quantization value;

subjecting, for each of said blocks, said replaced quantization value to inverse linear quantization using said quantization step-size Q to calculate a mean value M′

, and adding a difference DM, wherein DM=M′

−

M between the mean value M′ and

said mean value M to all the transform coefficients in the block;

calculating a mean value LM of the transform coefficients in the lowest frequency band after the addition of said difference DM; and

reconstructing a digital image signal in which said digital information has been embedded using the lowest frequency band after the addition of said difference DM and the other frequency bands.

6. The recording medium according to claim 5, wherein said step of replacing the quantization value replaces the quantization value with an odd value closest to the value of M/Q when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of M/Q when each of bits composing said digital information a logical value 0.

7. A digital information embedding apparatus for embedding inherent digital information in a digital image signal, said apparatus comprising:

a band dividing device operable to divide the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;

a block divider operable to divide the lowest frequency band out of the plurality of frequency bands into a plurality of blocks in accordance with a previously determined block size;

a quantization portion operable to calculate for each of the blocks, a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization, using a previously determined quantization step-size Q, wherein Q is an integer of not less than one, to calculate a quantization value;

a signal replacement portion operable to replace the quantization value for each of the blocks, on the basis of the quantization value and the value of said digital information to be embedded, which correspond to the block;

a mean difference addition portion operable to subject the replaced quantization value, for each of the blocks, to inverse linear quantization using the quantization step-size Q to calculate a mean value M′

, and to add a difference DM, wherein DM=M′

−

M, between the mean value M′ and

the mean value M to all the transform coefficients in the block;

a mean calculation portion operable to calculate a mean value LM of the transform coefficients in the lowest frequency band after the addition of the difference DM; and

a band synthesis portion for reconstructing a digital image signal in which the digital information has been embedded using the lowest frequency band after the addition of the difference DM and the other frequency bands.

8. The digital information embedding apparatus according to claim 7, wherein said signal replacement portion replaces the quantization value with an odd value closest to the value of M/Q when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of M/Q when each of bits composing the digital information takes a logical value 0.

9. A digital information embedding method of embedding inherent digital information in a digital image signal, said method comprising:

dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;

dividing the lowest frequency band out of said plurality of frequency bands into a plurality of blocks in accordance with a previously determined block size;

calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization, using a previously determined quantization step-size Q, wherein Q is an integer of not less than one, to calculate a quantization value;

replacing the quantization value for each of the blocks, on the basis of said quantization value and the value of the digital information to be embedded which correspond to the block;

subjecting the replaced quantization value for each of the blocks to inverse linear quantization using said quantization step-size Q to calculate a mean value M′

, and adding a difference DM, wherein DM=M′

−

M, between the mean value M′ and

the mean value M to all the transform coefficients in the block;

calculating a mean value LM of the transform coefficients in the lowest frequency band after the addition of the difference DM; and

reconstructing a digital image signal in which the digital information has been embedded using the lowest frequency band after the addition of the difference DM and the other frequency bands.

10. The digital information embedding method according to claim 9, wherein said replacing the quantization value comprises replacing the quantization value with an odd value closest to the value of M/Q when each of bits composing the digital information takes a logical value 1, and replacing the quantization value with an even value closest to the value of M/Q when each of bits composing said digital information takes a logical value 0.

11. A computer program embodied on a computer readable medium for use with a computer for embedding inherent digital information in a digital image signal, said computer program comprising:

computer readable program code for dividing a digital image signal into a plurality of frequency bands to obtain transform coefficients using either discrete wavelet transform or sub-band division;

computer readable program code for dividing the lowest frequency band out of the plurality of frequency bands into a plurality of blocks in accordance with a previously determined block size;

computer readable program code for calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization, using a previously determined quantization step-size Q, wherein Q is an integer of not less than one, to calculate a quantization value;

computer readable program code for replacing the quantization value for each of the blocks, on the basis of the quantization value and the value of said digital information to be embedded, which correspond to the block;

computer readable program code for subjecting the replaced quantization value, for each of the blocks, to inverse linear quantization using the quantization step-size Q to calculate a mean value M′

, and adding a difference DM, wherein DM=M′

−

M, between the mean value M′ and

the mean value M to all the transform coefficients in the block;

computer readable program code for calculating a mean value LM of the transform coefficients in the lowest frequency band after the addition of the difference DM; and

computer readable program code for reconstructing a digital image signal in which the digital information has been embedded using the lowest frequency band after the addition of the difference DM and the other frequency bands.

12. The computer readable program according to claim 11, wherein said computer readable program code for replacing the quantization value comprises computer readable program code for replacing the quantization value with an odd value closest to the value of M/Q when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of M/Q when each of bits composing the digital information takes a logical value 0.

13. A digital information embedding apparatus for embedding inherent digital information in a digital image signal, said apparatus comprising:

a band dividing device operable to divide the digital image signal into transform coefficients over a plurality of frequency bands;

a block divider operable to divide one frequency band out of the plurality of frequency bands into a plurality of blocks in accordance with a previously determined block size;

a quantization portion operable to calculate for each of the blocks, a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization, using a previously determined quantization step-size Q, wherein Q is an integer of not less than one, to calculate a quantization value,

a signal replacement portion operable to replace the quantization value for each of the blocks, on the basis of the quantization value and the value of said digital information to be embedded, which correspond to the block;

a mean difference addition portion operable to subject the replaced quantization value, for each of the blocks, to inverse linear quantization using the quantization step-size Q to calculate a mean value M′

, and to add a difference DM, wherein DM=M′

−

M, between the mean value M′ and

the mean value M to all the transform coefficients in the block;

a mean calculation portion operable to calculate a mean value LM of the transform coefficients in the frequency band after the addition of the difference DM; and

a band synthesis portion for reconstructing a digital image signal in which the digital information has been embedded using the frequency band after the addition of the difference DM and the other frequency bands.

14. The digital information embedding apparatus according to claim 13, wherein said signal replacement portion replaces the quantization value with an odd value closest to the value of M/Q when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of M/Q when each of bits composing the digital information takes a logical value 0.

15. A digital information embedding method of embedding inherent digital information in a digital image signal, said method comprising:

dividing the digital image signal into transform coefficients over a plurality of frequency bands;

dividing a frequency band out of said plurality of frequency bands into a plurality of blocks in accordance with a previously determined block size;

calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization, using a previously determined quantization step-size Q, wherein Q is an integer of not less than one, to calculate a quantization value;

replacing the quantization value for each of the blocks, on the basis of said quantization value and the value of the digital information to be embedded, which correspond to the block;

subjecting the replaced quantization value for each of the blocks to inverse linear quantization using said quantization step-size Q to calculate a mean value M′

, and adding a difference DM, wherein DM=M′

−

M, between the mean value M′ and

the mean value M to all the transform coefficients in the block;

calculating a mean value LM of the transform coefficients in the frequency band after the addition of the difference DM; and

reconstructing a digital image signal in which the digital information has been embedded using the frequency band after the addition of the difference DM and the other frequency bands.

16. The digital information embedding method according to claim 15, wherein said replacing the quantization value comprises replacing the quantization value with an odd value closest to the value of M/Q when each of bits composing the digital information takes a logical value 1, and replacing the quantization value with an even value closest to the value of M/Q when each of bits composing said digital information takes a logical value 0.

17. A computer program embodied on a computer readable medium for use with a computer for embedding inherent digital information in a digital image signal, said computer program comprising:

computer readable program code for dividing a digital image signal into a plurality of frequency bands to obtain transform coefficients;

computer readable program code for dividing a frequency band out of the plurality of frequency bands into a plurality of blocks in accordance with a previously determined block size;

computer readable program code for calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization, using a previously determined quantization step-size Q, wherein Q is an integer of not less than one, to calculate a quantization value;

computer readable program code for replacing the quantization value for each of the blocks, on the basis of the quantization value and the value of said digital information to be embedded, which correspond to the block;

computer readable program code for subjecting the replaced quantization value, for each of the blocks, to inverse linear quantization using the quantization step-size Q to calculate a mean value M′

, and adding a difference DM, wherein DM=M′

−

M, between the mean value M′ and

the mean value M to all the transform coefficients in the block;

computer readable program code for calculating a mean value LM of the transform coefficients in the frequency band after the addition of the difference DM; and

computer readable program code for reconstructing a digital image signal in which the digital information has been embedded using the frequency band after the addition of the difference DM and the other frequency bands.

18. The computer readable program according to claim 17, wherein said computer readable program code for replacing the quantization value comprises computer readable program code for replacing the quantization value with an odd value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 0.