Encoder and encoding method for electronic watermark, decoder and decoding method for electronic watermark, encoding and decoding program for electronic watermark, and recording medium for recording such program

• US 20030133591A1
• Filed: 10/18/2002
• Published: 07/17/2003
• Est. Priority Date: 10/22/2001
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Nishimura, Takayuki, Watanabe, Toshio, Nagao, Seiji, Watanabe, Kazumitsu
• Granted Patent: US 7,212,649 B2
• Time in Patent Office: Days
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• 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: G06T 2201/0061 Embedding of the watermark in each block of the image, e.g. segmented watermarking

Abstract

Disclosed is an encoder for forming electronic watermark information which allows detecting tampering of a digital content based on an electronic watermark embedded in the digital content, and limiting said tampered part. This encoder comprises means for dividing a subject digital content into multiple blocks, and means for independently forming the electronic watermark information in the individual blocks.

Claims

1. An encoder for forming electronic watermark information which detects tampering in a digital content, and limits a part of said tampering based on said electronic watermark embedded in said digital content, comprising:

means for dividing a subject digital content into multiple blocks; and

means for independently forming electronic watermark information in the individual blocks.

2. The encoder for electronic watermark according to claim 1 further comprising:

means for dividing the blocks to be divided such that a region of the block overlaps blocks neighboring on the upper, lower, left, and right sides in place of said means for dividing said digital content into multiple blocks; and

means for associating the electronic watermark information formed by the means for independently forming electronic watermark information in the individual blocks with each other by means of the overlap region between said blocks,

said electronic watermark being formed so as to detect an exchange between said blocks as tampering.

3. The encoder for electronic watermark according to claim 2 further comprising means for arbitrarily changing the size of the multiple divided blocks, and the overlap regions between the blocks in place of the means for dividing said digital content into multiple blocks.

4. The encoder for electronic watermark according to claim 1, wherein the means for independently forming electronic watermark information in said blocks forms said electronic watermark information by means of a hash function (randomizing) which uses plurality of data of a digital content embedded with an electronic watermark immediately before, a secret key, the date of executing the process, an apparatus production number, and the like as seed data.

5. The encoder for electronic watermark according to claim 4, wherein the number of successive pixels in individual regions of the digital content embedded with a digital watermark immediately before is used as the data of the digital content embedded with a digital watermark immediately before used as said seed data for the hash function (randomizing).

6. The encoder for electronic watermark according to claim 4, wherein odd/even of a pixel value of individual pixels in a multi-valued image of the digital content is matched using odd/even of an integer of a result of the randomizing by said hash function (randomizing) used for said means for forming electronic watermark information.

7. The encoder for electronic watermark according to claim 4, wherein odd/even of the number of successive pixels in individual regions in a binary image of the digital content is matched using odd/even of an integer of a result of the randomizing by said hash function (randomizing) used for said means for forming electronic watermark information.

8. The encoder for electronic watermark according to claim 4, wherein regions are formed based on a threshold for pixel values of individual pixels in a multi-valued image of the digital content, and odd/even of the number of successive pixels in the individual regions is matched using odd/even of an integer of a result of the randomizing of said hash function (randomizing) used for said means for forming electronic watermark information.

9. The encoder for electronic watermark according to claim 1 further comprising means for embedding said electronic watermark while positions for applying an electronic watermark are skipped in said digital content so as to restrain said digital content from degrading.

10. The encoder for electronic watermark according to claim 1 further comprising:

means for skipping positions for applying said electronic watermark in said digital content; and

means for embedding said electronic watermark at a boundary between successive pixels in said digital content,

wherein said digital content is restrained from degrading.

11. The encoder for electronic watermark according to claim 10, wherein means for arbitrarily changing the positions for skipping said electronic watermark is added to said means for skipping positions for applying the electronic watermark in said digital content.

12. An encoder for electronic watermark, wherein information indicating that said electronic watermark is embedded is recorded in a file header of said digital content when said digital content with said embedded electronic watermark is created by the encoder for electronic watermark according to claim 1, and then is recorded on a recording medium.

13. An encoder for electronic watermark, wherein the encoder for electronic watermark according to claim 1 is added to a digital camera, a subject is pictured as a digital content by imaging means, and the digital content is recorded on a recording medium while said electronic watermark is embedded.

26. A decoder for electronic watermark for reading out and decoding the electronic watermark embedded in a digital content by the encoder for electronic watermark according to claim 1, comprising:

means for reading out the electronic watermark information individually formed for multiple divided blocks;

means for decoding said electronic watermark information; and

means for detecting an existence of a tampered part in said digital content based on the result from said decoding means.

27. The decoder for electronic watermark according to claim 26 further comprising means for showing a block including said tampered part detected by said means for detecting an existence of a tampered part in the digital content as a color inversion pattern, a black fill pattern, a white fill pattern, a color fill pattern other than the black and white fills, and the like so as to visually identify the tampered part.

14. An encoding method for electronic watermark for forming electronic watermark information which detects tampering in a digital content, and limits a part of said tampering based on said electronic watermark embedded in said digital content, comprising the steps of:

dividing a subject digital content into multiple blocks; and

independently forming electronic watermark information in the individual blocks.

15. The encoding method for electronic watermark according to claim 14 further comprising the steps of:

dividing the blocks to be divided such that a region of the block overlaps blocks neighboring on the upper, lower, left, and right sides corresponding to the means for dividing the digital content into multiple blocks; and

associating the electronic watermark information formed by the means for independently forming electronic watermark information in the individual blocks with each other by means of the overlap region between said blocks,

said electronic watermark being formed so as to detect an exchange between said blocks as tampering.

16. The encoding method for electronic watermark according to claim 15 further comprising the step of arbitrarily changing the size of the multiple divided blocks, and the overlap region between the blocks so as to divide said blocks into arbitrary sizes when said digital content is divided into multiple blocks.

17. The encoding method for electronic watermark according to claim 14, wherein the electronic watermark information is independently formed in said blocks by means of a hash function (randomizing) while plurality of data of a digital content embedded with an electronic watermark immediately before, a secret key, the data of executing the process, an apparatus production number, and the like are used as seed data.

18. The encoding method for electronic watermark according to claim 17, wherein the number of successive pixels in individual regions of the digital content embedded with a digital watermark immediately before is used as the data of the digital content embedded with a digital watermark immediately before used as said seed data for the hash function (randomizing).

19. The encoding method for electronic watermark according to claim 17, wherein odd/even of a pixel value of individual pixels in a multi-valued image of the digital content is matched using odd/even of an integer of a result of the randomizing by said hash function (randomizing) used for said means for forming electronic watermark information.

20. The encoding method for electronic watermark according to claim 17, wherein odd/even of the number of successive pixels in individual regions in a binary image of the digital content is matched using odd/even of an integer of a result of the randomizing by said hash function (randomizing) used for said means for forming electronic watermark information.

21. The encoding method for electronic watermark according to claim 17, wherein regions are formed based on a threshold for pixel values of individual pixels in a multi-valued image of the digital content, and odd/even of the number of successive pixels in the individual regions is matched using odd/even of an integer of a result of the randomizing of said hash function (randomizing) used for said means for forming electronic watermark information.

22. The encoding method for electronic watermark according to claim 14 further comprising the step of embedding said electronic watermark while positions for applying an electronic watermark are skipped in said digital content so as to restrain said digital content from degrading.

23. The encoding method for electronic watermark according to claim 14 further comprising the steps of:

skipping positions for applying said electronic watermark in said digital content; and

embedding said electronic watermark at a boundary between successive pixels in said digital content,

wherein said digital content is restrained from degrading.

24. The encoding method for electronic watermark according to claim 22, wherein arbitrarily changing the positions for embedding the electronic watermark by skipping positions for applying said electronic watermark in said digital content arbitrarily selects a range of degradation of said digital content.

25. An encoding method for electronic watermark, wherein information indicating that an electronic watermark is embedded is recorded in a file header of the digital content when said digital content with the embedded electronic watermark is created by the encoding method for electronic watermark according to claim 14, and then the digital content is recorded on a recording medium.

28. A decoding method for electronic watermark for reading out and decoding the electronic watermark embedded in a digital content by the encoding method for electronic watermark according to claim 14, comprising the steps of:

reading out the electronic watermark information individually for the multiple divided blocks;

decoding said electronic watermark information; and

detecting an existence of a tampered part in said digital content.

29. The decoding method for electronic watermark according to claim 28 further comprising the step of showing a block including said tampered part detected based on reading out and decoding the electronic watermark information in said digital content as a color inversion pattern, a black fill pattern, a white fill pattern, a color fill other than the black and white fills, and the like so as to visually identify the tampered part.

30. An encoding and decoding program for electronic watermark for encoding to form electronic watermark information which detects tampering in a digital content, and limits a part of said tampering based on said electronic watermark embedded in said digital content, and for decoding said electronic watermark for showing a tampered part when said tampered part is detected, on an information processing apparatus, wherein said information processing apparatus executes a function for dividing a subject digital content into multiple blocks, a function for independently forming electronic watermark information in the individual blocks, a function for reading out the electronic watermark information individually for the multiple divided blocks, and a function for decoding said electronic watermark information, and then said information processing apparatus detects a tempered part, limits said tampered part to a block, and shows the tampered part for the individual blocks.

31. The encoding and decoding program for electronic watermark according to claim 30, wherein said information processing apparatus executes a function for dividing the blocks to be divided such that a region of the blocks overlaps blocks neighboring on the upper, lower, left, and right sides, and a function for associating the electronic watermark information formed by the function for independently forming electronic watermark information in the individual blocks with each other by means of the overlap region between said blocks when said function for dividing a subject digital content into multiple blocks is executed, and forms said electronic watermark so as to detect an exchange between said blocks as tampering.

32. The encoding and decoding program for electronic watermark according to claim 31, wherein said information processing apparatus executes a function for arbitrarily changing the size of the multiple divided blocks, and the overlap region between the blocks when the function for dividing said digital content into multiple blocks is executed.

33. The encoding and decoding program for electronic watermark according to claim 30, wherein said information processing apparatus executes a function for independently forming electronic watermark information in said blocks to form said electronic watermark information by means of a hash function (randomizing) which uses plurality of data of a digital content embedded with an electronic watermark immediately before, a secret key, the data of executing the process, an apparatus production number, and the like as seed data.

34. The encoding and decoding program for electronic watermark according to claim 33, wherein the number of successive pixels in individual regions of the digital content embedded with a digital watermark immediately before is used as the data of the digital content embedded with a digital watermark immediately before used as said seed data for the hash function (randomizing).

35. The encoding and decoding program for electronic watermark according to claim 33, wherein odd/even of a pixel value of individual pixels in a multi-valued image of the digital content is matched using odd/even of an integer of a result of the randomizing by said hash function (randomizing) used when said function for forming electronic watermark information is executed by said information processing apparatus.

36. The encoding and decoding program for electronic watermark according to claim 33, wherein odd/even of the number of successive pixels in individual regions in a binary image of the digital content is matched using odd/even of an integer of a result of the randomizing by said hash function (randomizing) used when said function for forming electronic watermark information is executed by said information processing apparatus.

37. The encoding and decoding program for electronic watermark according to claim 33, wherein regions are formed based on a threshold for pixel values of individual pixels in a multi-valued image of the digital content, and odd/even of the number of successive pixels in the individual regions is matched using odd/even of an integer of a result of the randomizing of said hash function (randomizing) used when said function for forming electronic watermark information is executed by said information processing apparatus.

38. The encoding and decoding program for electronic watermark according to claim 30, wherein said information processing apparatus executes a function for embedding said electronic watermark while positions for applying an electronic watermark are skipped in said digital content so as to restrain said digital content from degrading.

39. The encoding and decoding program for electronic watermark according to claim 30, wherein said information processing apparatus executes a function for skipping positions for applying said electronic watermark in said digital content, and a function for embedding said electronic watermark at a boundary between successive pixels in said digital content, and said digital content is restrained from degrading.

40. The encoding and decoding program for electronic watermark according to claim 38, wherein said information processing apparatus executes a function for arbitrarily changing the positions for skipping the electronic watermark in the function for skipping positions for applying said electronic watermark in said digital content so as to select a range of degradation of said digital content.

41. The encoding and decoding program for electronic watermark according to claim 30, wherein said information processing apparatus executes a function for detecting a tampered part in the digital content based on said decoded electronic watermark information, and a function for showing a block including said tampered part as a color inversion pattern, a black fill pattern, a white fill pattern, a color fill pattern other than the black and white fills, and the like so as to visually identify the tampered part when said information processing apparatus executes the function for decoding said electronic watermark information.

42. A recording medium for recording the encoding and decoding program for electronic watermark according to claim 30 so as to be readable for functioning on an information processing apparatus.