Information processing apparatus and its control method, computer program, and storage medium

• US 20020199106A1
• Filed: 02/08/2002
• Published: 12/26/2002
• Est. Priority Date: 02/09/2001
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Hayashi, Junichi
• Granted Patent: US 7,146,502 B2
• Time in Patent Office: Days
• US Class Current: 713/176
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• CPC Class Codes: H04N 1/00127 Connection or combination of a still picture apparatus with another apparatus, e.g. for storage, processing or transmission of still picture signals or of information associated with a still picture
• 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 1/32229 with selective or adaptive application of the additional information, e.g. in selected regions of the image H04N1/32213 takes precedence
• CPC Class Codes: H04N 1/32283 Hashing
• CPC Class Codes: H04N 2201/3236 Details of authentication information generation
• CPC Class Codes: H04N 2201/327 which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 2201/3281 Encryption; Ciphering

Abstract

According to this invention, whether or not information has been tampered with can be detected while authentication information is set to be inseparable from digital information, and original digital data can be restored as long as it is free from tampering.

For this purpose, when authentication information is embedded into digital information input by an image input unit (201), a Hash value calculation unit (202) generates authentication information based on that digital information, an encryption unit (203) encrypts the authentication information using an encryption key, and a digital watermarking unit (204) embeds the encrypted information in the digital information as a digital watermark.

Claims

1. An information processing apparatus for embedding authentication information into digital information, comprising:

means for generating authentication information on the basis of the digital information to which the authentication information is to be embedded; and

digital watermarking means for embedding the generated authentication information into the digital information with the digital information being exactly restorable.

2. The apparatus according to claim 1, wherein the authentication information is a digital signature.

3. The apparatus according to claim 1, further comprising encryption means for encrypting the digital information using a secret key, and wherein the digital signature is data obtained by encrypting the digital information using the secret key.

4. The apparatus according to claim 1, further comprising Hash value calculation means for calculating a Hash value of the digital information, and encryption means for encrypting the Hash value using a secret key, and wherein the digital signature is data obtained by encrypting the Hash value of the digital information using the secret key.

5. The apparatus according to claim 1, wherein the authentication information is MAC.

6. The apparatus according to claim 5, further comprising Hash value calculation means for calculating a Hash value of the digital information, and arithmetic operation means for arithmetically operating the Hash value using a secret key, and wherein the MAC is data obtained by arithmetically operating the Hash value of the digital information using the secret key.

7. The apparatus according to claim 2, wherein the authentication information includes at least one of date information, position information, time information, unique information of an apparatus, and unique information of a person who signed, in addition to the digital signature.

8. An information processing apparatus for authenticating digital information in which authentication information is embedded as a digital watermark, comprising:

means for extracting, as first authentication information, the authentication information embedded as the digital watermark from the digital information;

digital watermark removal means for removing the extracted authentication information from the digital information as the digital watermark, and restoring tentative original digital information;

generation means for generating second authentication information on the basis of the tentative original digital information restored by removing the digital watermark by said digital watermark removal means; and

comparison means for comparing the first authentication information with second authentication information.

9. The apparatus according to claim 8, further comprising informing means for, when the first authentication information and second authentication information are equal to each other, informing that the input digital information has not been tampered with, and for, when the first authentication information and second authentication information are not equal to each other, informing that the input digital information has been tampered with.

10. The apparatus according to claim 8, wherein the authentication information is a digital signature.

11. The apparatus according to claim 8, further comprising decryption means for decrypting the digital signature using a public key, and wherein said comparison means compares information obtained by decrypting the second authentication information with the first authentication information.

12. The apparatus according to claim 8, further comprising Hash value calculation means for calculating a Hash value of the digital information from which the digital watermark has been removed, and decryption means for decrypting the digital signature using a public key, and wherein said comparison means compares information obtained by decrypting the second authentication information using the public key, with the Hash value.

13. The apparatus according to claim 8, wherein the authentication information is MAC.

14. The apparatus according to claim 12, further comprising Hash value calculation means for calculating a Hash value of the digital information from which the digital watermark has been removed, and arithmetic operation means for arithmetically operating the MAC using a secret key, and wherein said comparison means compares information obtained by decrypting the MAC using the secret key with the Hash value.

15. The apparatus according to claim 8, wherein the authentication information includes at least one of date information, position information, time information, unique information of an apparatus, and unique information of a person who signed, in addition to the digital signature.

19. A storage medium storing a computer program cited in claim 18.

16. A method of controlling an information processing apparatus for embedding authentication information into digital information, comprising:

the step of generating authentication information on the basis of the digital information to which the authentication information is to be embedded; and

the digital watermarking step of embedding the generated authentication information into the digital information with the digital information being restorable.

17. A method of controlling an information processing apparatus for authenticating digital information in which authentication information is embedded as a digital watermark, comprising:

the step of extracting, as first authentication information, the authentication information embedded as the digital watermark from the digital information;

the digital watermark removal step of removing the extracted authentication information from the digital information as the digital watermark, and restoring tentative original digital information;

the generation step of generating second authentication information on the basis of the tentative original digital information restored by removing the digital watermark in the digital watermark removal step; and

the comparison step of comparing the first authentication information with second authentication information.

18. A computer program which is loaded and executed by a computer to make the computer function as an information processing apparatus for embedding authentication information into digital information, comprising:

a program code of the step of generating authentication information on the basis of the digital information to which the authentication information is to be embedded; and

a program code of the digital watermarking step of embedding the generated authentication information into the digital information with the digital information being restorable.

20. A computer program which is loaded and executed by a computer to make the computer function as an information processing apparatus for authenticating digital information in which authentication information is embedded as a digital watermark, comprising:

a program code of the step of extracting, as first authentication information, the authentication information embedded as the digital watermark from the digital information;

a program code of the digital watermark removal step of removing the extracted authentication information from the digital information as the digital watermark, and restoring tentative original digital information;

a program code of the generation step of generating second authentication information on the basis of the tentative original digital information restored by removing the digital watermark in the digital watermark removal step; and

a program code of the comparison step of comparing the first authentication information with second authentication information.

21. A storage medium storing a computer program cited in claim 20.

22. An information embedding apparatus for embedding additional information into elements which form digital data by adding/subtracting a value to/from the elements, comprising:

detection means for detecting an element which has a value that exceeds a range the element can assume after addition/subtraction;

generation means for generating actual embedding information by combining the additional information and information detected by said detection means; and

embedding means for excluding the element which exceeds the range the element can assume after addition/subtraction from an embedding process upon embedding into the digital data, and embedding the actual embedding information generated by said generation means into the elements, which fall within the range the element can assume, as a digital watermark.

23. The apparatus according to claim 22, wherein the digital data is image data, and

said detection means detects a pixel position where a pixel value exceeds a range the pixel value can assume after addition/subtraction.

24. The apparatus according to claim 22, further comprising encoding means for compression-encoding at least one of the additional information and the information detected by said detection means, and wherein said generation means generates the actual embedding information on the basis of an encoding result of said encoding means.

25. The apparatus according to claim 22, further comprising encryption means for encrypting at least one of the additional information and the information detected by said detection means, and wherein said generation means generates the actual embedding information on the basis of an encryption result of said encryption means.

26. The apparatus according to claim 22, further comprising encoding means for converting at least one of the additional information and the information detected by said detection means into an error correction code, and wherein said generation means generates the actual embedding information on the basis of a conversion result of said encoding means.

27. The apparatus according to claim 22, further comprising correction means for correcting the digital data to reduce the number of elements, which have values that exceed the range the element can assume after addition/subtraction, in the digital data, and

wherein said generation means generates the actual embedding information by embedding information indicating correction contents of said correction means.

28. An information restoration apparatus for receiving digital data in which information is embedded by an information embedding apparatus cited in claim 22, and restoring original digital data, comprising:

digital watermark extraction means for extracting information embedded into the input digital data; and

digital watermark removal means for removing the embedded information, from the elements which have undergone an embedding process, on the basis of information which specifies elements excluded from the embedding process, and restoring original digital data.

29. The apparatus according to claim 28, further comprising decoding means for expanding and decoding at least one of the additional information extracted by said digital watermark extraction means, the information indicating the elements excluded from the embedding process, and

wherein said digital watermark removal means removes a digital watermark on the basis of a result decoded by said decoding means.

30. The apparatus according to claim 28, further comprising decoding means for decrypting and decoding at least one of the additional information extracted by said digital watermark extraction means, the information indicating the elements excluded from the embedding process, and

wherein said digital watermark removal means removes a digital watermark on the basis of a result decoded by said decoding means.

31. The apparatus according to claim 28, further comprising decoding means for decoding an error correction code of at least one of the additional information extracted by said digital watermark extraction means, the information indicating the elements excluded from the embedding process, and

wherein said digital watermark removal means removes a digital watermark on the basis of a result decoded by said decoding means.

33. A method of controlling an information restoration apparatus for receiving digital data in which information is embedded by an information embedding apparatus cited in claim 22, and restoring original digital data, comprising:

the digital watermark extraction step of extracting information embedded into the input digital data; and

the digital watermark removal step of removing the embedded information, from the elements which have undergone an embedding process, on the basis of information which specifies elements excluded from the embedding process, and restoring original digital data.

35. A computer program which is loaded and executed by a computer to make the computer function as an information restoration apparatus for receiving digital data in which information is embedded by an information embedding apparatus cited in claim 22, and restoring original digital data, comprising:

a program code of the digital watermark extraction step of extracting information embedded into the input digital data; and

a program code of the digital watermark removal step of removing the embedded information, from the elements which have undergone an embedding process, on the basis of information which specifies elements excluded from the embedding process, and restoring original digital data.

36. A storage medium storing a computer program cited in claim 34.

37. A storage medium storing a computer program cited in claim 35.

32. A method of controlling an information embedding apparatus for embedding additional information into elements which form digital data by adding/subtracting a value to/from the elements, comprising:

the detection step of detecting an element which has a value that exceeds a range the element can assume after addition/subtraction;

the generation step of generating actual embedding information by combining the additional information and information detected in the detection step; and

the embedding step of excluding the element which exceeds the range the element can assume after addition/subtraction from an embedding process upon embedding into the digital data, and embedding the actual embedding information generated in the generation step in the elements, which fall within the range the element can assume, as a digital watermark.

34. A computer program which is loaded and executed by a computer to make the computer function as an information embedding apparatus for embedding additional information into elements which form digital data by adding/subtracting a value to/from the elements, comprising:

a program code of the detection step of detecting an element which has a value that exceeds a range the element can assume after addition/subtraction;

a program code of the generation step of generating actual embedding information by combining the additional information and information detected in the detection step; and

a program code of the embedding step of excluding the element which exceeds the range the element can assume after addition/subtraction from an embedding process upon embedding into the digital data, and embedding the actual embedding information generated in the generation step into the elements, which fall within the range the element can assume, as a digital watermark.