JP2007080071A - System having alteration detecting function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alteration detection system which reads a file including verification data and generates the verification data again after editing to the file. <P>SOLUTION: The system having an alteration detecting function is provided with: a file reading means for reading the file including the verification data required for alteration detection; a verification data generation means for generating the verification data for information after alteration of the file, and a recording means for adding the verification data obtained by the generation means to the file. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a modification detection system that enables verification of whether or not information has been modified.

  In recent years, digital cameras that digitize and store optical images of subjects have been put into practical use.

While image data taken with a digital camera can be easily taken into a personal computer, there is a problem that it can be easily modified on the personal computer. Therefore, there is a problem that the reliability of the image data taken with the digital camera is lower than that of the silver salt photograph and the evidence ability is poor. Therefore, in recent years, there has been proposed a modification detection system having a function capable of adding a digital signature to image data captured by a digital camera and verifying whether the information has been modified. A conventional alteration detection system using a digital camera is disclosed in, for example, US Pat. No. 5,499,294 and Japanese Patent Laid-Open No. 9-200730.
US5499294 Japanese Patent Application Laid-Open No. 9-2000730

  A lot of metadata such as shooting information and image processing information is added to image data shot by a digital camera, and editing is often performed on these metadata. However, the conventional modification detection system has a problem that the editing and modification detection as described above cannot be performed at the same time, because it is determined that the modification is unconditionally performed when the file to which the verification data is added is edited.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a modification detection system that can read a file including verification data and generate verification data again after editing the file.

  The invention according to claim 1 is a system having a modification detection function, a file reading means for reading a file including verification data necessary for modification detection, and verification data generation for generating verification data for the modified information of the file And a recording means for appending the verification data obtained by the generating means to the file.

  According to a second aspect of the present invention, in a system having a modification detection function, file reading means for reading a file including verification data necessary for modification detection, and verification data generation for generating verification data for information after modification of the file And a recording means for rewriting the verification data of the file with the verification data obtained by the generating means.

  According to a third aspect of the present invention, in a system having a modification detection function, file reading means for reading a file including verification data necessary for modification detection, and verification data generation for generating verification data for information after modification of the file Means and recording means for recording in a file separate from the file.

  According to a fourth aspect of the present invention, there is provided a file reading means for reading a file including verification data required for detection of a change and a verification data generation for generating verification data for the information after the change of the file in a system having a change detection function. Means and recording means for recording history information of verification data for the file.

  In the alteration detection system according to claim 1, by newly generating a digital signature from information after editing the information with a digital signature and adding the digital signature, the information with the digital signature can be easily regenerated, In addition, the verification system can detect alterations to the edited data.

  In the alteration detection system according to claim 2, a digital signature is newly generated from information after editing with respect to information with a digital signature, and the digital signature is rewritten to the digital signature so that the amount of information is not increased unnecessarily. Information can be regenerated and the verification system can detect changes to the edited data.

  In the alteration detection system according to claim 3, a new digital signature is generated from the edited information with respect to the information with the digital signature, and is recorded in another file including the digital signature and the edited information. The digitally signed information can be newly regenerated while leaving the file, and the verification system can detect alterations to the edited data.

  In the modification detection system according to the fourth aspect, the history of editing the information with the digital signature can be confirmed by recording the history information in the information in which the digital signature is generated one or more times.

Example 1
Hereinafter, a first exemplary embodiment suitable for the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration example of a modification verification system according to the first embodiment.

  The information generation unit 10 has a function of generating or editing information data, a function of generating a digital signature of the information data, and a function of generating an information file with a digital signature.

  The verification unit 20 has a function of verifying the integrity of information data using a digital signature and detecting whether the information data has been altered.

  The information generation unit 10 and the verification unit 20 may be an imaging device such as a digital camera, a digital video camera, or a scanner, or may be an electronic device having a camera unit. Further, it may be a facsimile machine having an image reading unit, an electronic device such as a copying machine, or a personal computer.

  FIG. 2 is a block diagram illustrating a main functional configuration of a digital camera as the information generation unit 10 in the present embodiment.

  The imaging unit 201 includes an optical sensor such as a CCD (charge coupled device) and various processing processors, and is an imaging unit that generates image data of a subject in accordance with instructions from a user or an operation program.

  The hash function calculation unit 202 is a calculation unit that generates a hash value (digest data) of image data using the hash function H. The hash function H may be any one of MD-2MD-5, SHA-1, RIPEMD-128, and RIPEMD-160, or other hash functions.

  The signature generation unit 204 is an operation unit that performs an operation process on the digest data generated by the hash function operation unit 202 with the secret key Ks to generate a digital signature of the image data.

  The memory 205 is a memory that stores a unique ID (for example, a manufacturing number or a serial number of the information generation unit 10) that is information unique to the information generation unit 10.

  The image file generation unit 206 is an image file generation unit that generates an image file (image file with a digital signature) including image data and a digital signature. For example, the digital signature is added to the header portion of the image file. The file format of an image file with a digital signature is an extension of any of JIFF (JPEG File Interchange Format), TIFF (Tagged Image File Format), and GIF (Graphics Interchange Format). Alternatively, other image file formats may be used.

  The removable medium 207 is a removable medium (detachable storage medium) such as a magnetic disk, an optical disk, or a memory card.

  The media control unit 208 is a media control unit having a function of storing an image file with a digital signature in the removable medium 207 and a function of reading out an image file with a digital signature from the removable medium 207.

  The interface unit 209 is an interface unit that transmits an image file with a digital signature read from the removable medium 207 to the verification unit 20.

  The operation unit 210 is an operation unit including a trigger switch that instructs to capture or generate image data of a subject.

  The control unit 211 is a control unit including a memory and a microcomputer that executes a control program stored in the memory.

  FIG. 3 is a block diagram illustrating a main functional configuration of the verification unit 20 according to the present embodiment.

  The media control unit 301 is a media control unit that reads an image file with a digital signature from the removable medium 207.

  The interface unit 309 is an interface unit that receives an image file with a digital signature transmitted from the information generation unit 10 to the verification unit 20.

  The storage unit 302 is a storage unit that stores an image file with a digital signature.

  The hash function calculation unit 303 is a hash function calculation unit that generates a hash value (digest data) of image data using the hash function H.

  The memory 304 is a memory that stores the table T1. The table T1 is a management table in which a plurality of unique IDs and public keys Kp corresponding to the unique IDs are registered.

  The arithmetic processing unit 305 is an arithmetic unit that generates digest data by performing arithmetic processing on the digital signature with the public key Kp.

  The image verification unit 306 is an image verification unit that verifies whether image data has been altered.

  The display unit 307 is a display unit that displays display information indicating display information indicating a verification result in the image verification unit 306.

  The control unit 308 has a memory and a microcomputer that executes a control program stored therein, and is a control unit that controls the operation of each unit of the verification unit 20.

  FIG. 4 is a diagram for explaining the processing procedure of the modification verification system according to the first embodiment.

  Step S401: The imaging unit 201 generates image data of a subject, and supplies the generated image data and metadata to the hash function calculation unit 202 and the image file generation unit 206.

  Step S <b> 402: The hash function calculation unit 202 generates a hash value of the image data using the hash function H, and supplies the generated hash value to the signature generation unit 204.

  Step S403: The signature generation unit 204 processes the digest data with the secret key Ks to generate a digital signature of the image data. The signature generation unit 204 supplies the generated digital signature 1 to the image file generation unit 206.

  Step S404: The image file generation unit 206 generates an image file (image file with a digital signature) including the digital signature 1, unique ID, image data, and metadata, and supplies the generated image file to the media control unit 208. The media control unit 208 writes the image file with the digital signature generated by the image file generation unit 206 into the removable medium 207. Note that an image file with a digital signature is generated every time one piece of image data is generated.

  Step S405: The user inputs an image file with a digital signature stored in the removable medium 207 to the verification unit 20 via the removable medium 207 or the interface unit 209. When inputting via the removable medium 207, the media control unit 301 reads an image file with a digital signature from the removable medium 207 and stores the read image file in the storage unit 302. On the other hand, when inputting via the interface unit 209, the interface unit 309 receives the image file with the digital signature transmitted from the information generation unit 10 to the verification unit 20, and stores the received image file in the storage unit 302.

  Step S406: The arithmetic processing unit 305 refers to the table T1 in the memory 304 and acquires the public key Kp corresponding to the unique ID. An example of the table T1 is shown in FIG. For example, when the unique ID is “001”, the public key Kp corresponding to the unique ID is “0x3333”. In this way, the verification unit 20 obtains the public key Kp from the unique ID.

  Step S407: The arithmetic processing unit 305 performs arithmetic processing on the digital signature with the public key Kp, and restores the digest data.

  Step S408: The hash function calculation unit 303 uses the hash function H to generate digest data of the image data.

  Step S409: The image verification unit 306 compares the digest data restored by the calculation processing unit 305 with the digest data generated by the hash function calculation unit 303 to verify whether the image data has been altered. .

  If the digitally signed image file has not been altered, the two digest data match. In this case, the image verification unit 306 determines “no modification”, and the display unit 307 displays information indicating that no modification of the image data has been detected.

  On the other hand, digest data does not match when an image file with a digital signature is altered. In this case, the image verification unit 306 determines that “there is modification”, and the display unit 307 displays display information indicating that the modification of the image data is detected.

  The subsequent steps show a processing procedure when an image file determined to be “no modification” is edited.

  Step S410: The edited image data and metadata are supplied to the hash function calculation unit 202 and the image file generation unit 206.

  Step S411: The digital signature 2 generated in the same manner as in Step S402 to Step 404 described above is supplied to the image file generation unit 206.

  Step S412: The image file generation unit 206 generates an image file (image file with a digital signature) including the digital signature 1, the digital signature 2, the unique ID, the edited image data, and metadata.

  As described above, according to the modification verification system in the first embodiment, even if an image file with a digital signature is edited, the verification unit 20 determines that the image file has not been modified. On the other hand, since the digital signature is newly added to the edited image file, the modification of the edited image file can be verified. Further, since the verification unit can verify that there is no modification, malicious modification can also be eliminated.

  In this embodiment, the digital signature data is used as the verification data. However, the present invention is not limited to this. For example, it is conceivable to use MAC data as the verification data. In this case, the information generation unit generates MAC data by performing an operation using the image data and the secret key Ks generated from the secret information A and the secret information B, and uses the data to generate an image file with verification data. Create As the calculation, an arithmetic process using an encryption algorithm may be considered for digest data of image data. At this time, the secret key Ks is used as key data.

  On the other hand, the verification unit 20 extracts MAC data from the image file with verification data, compares the data with the MAC data generated by performing the same operation as the information generation unit 10 and detects falsification. Do. If the two MAC data match, it is determined that the image file with verification data has not been altered. On the other hand, when the two MAC data match, it is determined that the image file with verification data has been altered.

  When the MAC data is used as verification data, the information generation unit 10 and the verification unit 20 need to secretly share the secret key Ks by some method.

  Moreover, although the present Example demonstrated the case where the information generation part 10 and the verification part 20 exist in another apparatus, even if the information generation part 10 and the verification part 20 are in the same apparatus, it is in another apparatus. Also good.

(Example 2)
FIG. 6 is a diagram for explaining the processing procedure of the modification verification system according to the second embodiment.

  Step S601: The imaging unit 201 generates image data of a subject, and supplies the generated image data and metadata to the hash function calculation unit 202 and the image file generation unit 206.

  Step S <b> 602: The hash function calculation unit 202 generates a hash value of image data using the hash function H, and supplies the generated hash value to the signature generation unit 204.

  Step S603: The signature generation unit 204 performs an arithmetic process on the digest data with the secret key Ks to generate a digital signature of the image data. The signature generation unit 204 supplies the generated digital signature 1 to the image file generation unit 206.

  Step S604: The image file generation unit 206 generates an image file (image file with a digital signature) including the digital signature 1, unique ID, image data, and metadata, and supplies the generated image file to the media control unit 208. The media control unit 208 writes the image file with the digital signature generated by the image file generation unit 206 into the removable medium 207. Note that an image file with a digital signature is generated every time one piece of image data is generated.

  Step S605: The user inputs an image file with a digital signature stored in the removable medium 207 to the verification unit 20 via the removable medium 207 or the interface unit 209. When inputting via the removable medium 207, the media control unit 301 reads an image file with a digital signature from the removable medium 207 and stores the read image file in the storage unit 302. On the other hand, when inputting via the interface unit 209, the interface unit 309 receives the image file with the digital signature transmitted from the information generation unit 10 to the verification unit 20, and stores the received image file in the storage unit 302.

  Step S606: The arithmetic processing unit 305 refers to the table T1 in the memory 304 and acquires the public key Kp corresponding to the unique ID. An example of the table T1 is shown in FIG. For example, when the unique ID is “001”, the public key Kp corresponding to the unique ID is “0x3333”. In this way, the verification unit 20 obtains the public key Kp from the unique ID.

  Step S607: The arithmetic processing unit 305 performs arithmetic processing on the digital signature with the public key Kp to restore the digest data.

  Step S608: The hash function calculation unit 303 generates digest data of the image data using the hash function H.

  Step S609: The image verification unit 306 compares the digest data restored by the arithmetic processing unit 305 with the digest data generated by the hash function calculation unit 303, and verifies whether the image data has been altered. .

  If the digitally signed image file has not been altered, the two digest data match. In this case, the image verification unit 306 determines “no modification”, and the display unit 307 displays information indicating that no modification of the image data has been detected.

  On the other hand, digest data does not match when an image file with a digital signature is altered. In this case, the image verification unit 306 determines that “there is modification”, and the display unit 307 displays display information indicating that the modification of the image data is detected.

  The subsequent steps show a processing procedure when an image file determined to be “no modification” is edited.

  Step S610: The edited image data and metadata are supplied to the hash function calculation unit 202 and the image file generation unit 206.

  Step S611: The digital signature 2 generated in the same manner as in Step S602 to Step 604 described above is supplied to the image file generation unit 206.

  Step S612: The image file generation unit 206 generates an image file (an image file with a digital signature) including a digital signature 2 in place of the original digital signature 1, a unique ID, edited image data and metadata, and modification history information. Generate.

  As described above, according to the modification verification system according to the second embodiment, even if an image file with a digital signature is edited, the verification unit 20 determines that the image file has not been modified. On the other hand, since the digital signature generated for the edited image file is rewritten and history information is recorded, the modification of the edited image file can be verified, and the modification history can be confirmed.

  In the present embodiment, the method of rewriting the digital signature 1 recorded in the original image file with the digital signature 2 generated from the edited data has been described. However, the original image file is left as it is before editing, and another file is created. As an example, an image file composed of edited data, digital signature 2 and the like may be generated.

One configuration example of a modification detection system in an embodiment of the present invention Main functional configuration example of the information generation unit 10 in the embodiment of the present invention Main functional configuration example of verification unit 20 in the embodiment of the present invention Processing procedure of the alteration detection system in the first embodiment An example of the table T1 in the embodiment of the present invention Processing procedure of the alteration detection system in the second embodiment

Claims (4)

In a system having a modification detection function,
A file reading means for reading a file including verification data necessary for alteration detection;
Verification data generation means for generating verification data for the modified information of the file;
Recording means for appending verification data obtained by the generating means to the file;
A system comprising: In a system having a modification detection function,
A file reading means for reading a file including verification data necessary for alteration detection;
Verification data generation means for generating verification data for the modified information of the file;
Recording means for rewriting the verification data of the file with the verification data obtained by the generating means;
A system comprising: In a system having a modification detection function,
A file reading means for reading a file including verification data necessary for alteration detection;
Verification data generation means for generating verification data for the modified information of the file;
Recording means for recording in a file different from the file;
A system comprising: In a system having a modification detection function,
A file reading means for reading a file including verification data necessary for alteration detection;
Verification data generation means for generating verification data for the modified information of the file;
Recording means for recording history information of verification data for the file;
A system comprising:

Images