Tampering judgement system, encrypting system for judgement of tampering and tampering judgement method

• US 20030169456A1
• Filed: 11/26/2002
• Published: 09/11/2003
• Est. Priority Date: 03/08/2002
• Status: Active Grant

• Current Assignee: Oki Data Corporation (OKI Electric Industry Company Limited)
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Suzaki, Masahiko
• Granted Patent: US 7,440,143 B2
• Time in Patent Office: Days
• US Class Current: 358/3.28
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06T 2201/0061 Embedding of the watermark in each block of the image, e.g. segmented watermarking
• CPC Class Codes: G09C 5/00 Ciphering apparatus or methods not provided for in the preceding groups, e.g. involving the concealment or deformation of graphic data such as designs, written or printed messages
• CPC Class Codes: H04L 9/0861 Generation of secret information including derivation or calculation of cryptographic keys or passwords

Abstract

A tampering judgement system is provided which is capable of easily checking whether or not a printed document has been tampered. An image feature information extracting section extracts image feature information from a document image. An image feature information embedding section gives image feature information integrally as original image feature information to a document and a document image output section outputs the information as a printed document. When the printed document is given to the tampering judgement system, the image data is read by a document image reading section. An image feature information extracting section extracts image feature information contained in a document being an object for judgement on tampering. An embedding information extracting section extracts original image feature information from image data. A judging section compares original feature information with image feature information contained in the printed document and if a difference between them exceeds a predetermined threshold value, the document is judged to have been tampered.

Claims

1. A tampering judgement system comprising:

a document image output device having a first image feature information extracting section to extract first image feature information representing features of an image from a document image showing a specified document, an original image feature information adding section to add original image feature information representing said first image feature information extracted from said first image feature information extracting section to said document image, and an output section to output said document image to which said original image feature information has been added; and

a tampering judgement device having an original image feature information extracting section to extract said original image feature information from an output document image serving as said document image output by said output section, a second image feature information extracting section to extract second image feature information representing features of said image from said output document image, and a judging section to compare said first image feature information represented by said original image feature information extracted by said original image feature information extracting section with second image feature information extracted by said second image feature information extracting section to judge whether or not said output document image has been tampered based on a result from the comparison.

2. The tampering judgement system according to claim 1, wherein said judging section contained in said tampering judgement device, if a result from said comparison between said first image feature information represented by said original image feature information and said second image feature information shows that a difference between said first image feature information and said second image feature information exceeds a specified threshold value, judges that said output document image has been tampered.

3. The tampering judgement system according to claim 1, wherein said first image feature information extracting section divides said document image into a plurality of blocks and extracts said first image feature information for every block and wherein said second image feature information extracting section divides said output document image into said plurality of blocks and extracts said second image feature information for every block.

4. The tampering judgement system according to claim 1, wherein said original image feature information serves as information representing said first image feature information in a manner that said first image feature information is able to be optically read.

5. An encrypting system for judging whether or not a content of a specified document has been tampered comprising:

a document image output device having a first image feature information extracting section to extract first image feature information representing features of an image from a document image showing a specified document, a first encryption key generating section to generate first encryption key from said first image feature information, a hidden information encrypting section to encrypt specified hidden information using said first encryption key, an encrypted information adding section to add the encrypted hidden information to said document image, and an output section to output said document image to which said encrypted information has been added; and

a decoding device having an encrypted information extracting section to extract said encrypted information from an output document image serving as said document image output by said output section, a second image feature information extracting section to extract second image feature information representing features of an image from said output document image, a second encryption key generating section to generate a second encryption key from said second image feature information, and a decoding section to perform decoding processing on said extracted and encrypted information using said second encryption key.

6. The encrypting system according to claim 5, wherein said first image feature information extracting section divides said document image into a plurality of blocks and extracts said first image feature information for every block and wherein said second image feature information extracting section divides said output document image into said plurality of blocks and extracts said second image feature information for every block.

7. The encrypting system according to claim5, wherein said encrypted information serves as information representing said encrypted hidden information in a manner that said encrypted hidden information is able to be optically read.

8. A method for judging whether or not a document image has been tampered which has a document image outputting device and a tampering judgement device, said method comprising:

a first step of having said document image output device extract first image feature information representing features of an image from a document image representing a specified document, add original image feature information representing said extracted first image feature information to said document image and output said document image to which said original image feature information has been added; and

a second step of, after having completed said first step, having said tampering judgement device extract said original image feature information from an output document image serving as said output image, then extract second image feature information representing features of an image from said output document image and compare said first image feature information represented by said extracted original image feature information with said second image feature information and judge, based on a result from the comparison, whether or not said output document image has been tampered.