JP7389293B1 - Tampering detection system and tampering detection method - Google Patents

Abstract

[Problem] To reduce the burden of proving the integrity of electronic files.
A tampering detection system 1 of the present invention includes a calculation unit 11 that calculates original integrity information for an original electronic file, and stores the calculated original integrity information in the original electronic file as digital watermark information. a storage unit 12; a reading unit 13 that reads the original integrity information from a target electronic file that is the same target as the original electronic file; a reading unit 13 that reads the original integrity information read from the target electronic file; A comparison unit 14 is provided for comparing the electronic file with target integrity information calculated for the electronic file. The integrity information may be stored as metadata, tint block data, or a processing log associated with the watermark ID.
[Selection diagram] Figure 1

Description

The present invention relates to a tampering detection system, a recording material, and a tampering detection method.

In recent years, technological development regarding countermeasures against document tampering has been progressing, and related inventions have also been published. For example, Patent Document 1 discloses a document storage management system that can safely and reliably store and manage will-related documents written by the testator himself/herself. In the invention of Patent Document 1, a key pair consisting of a public key and a private key is created for a witness based on a public key cryptosystem, and an electronic certificate certifying that the public key has been issued to the witness is created. The public key is stored in association with the witness information regarding the witness, the document image data of the will-related document is temporarily stored in a temporary document storage means in association with the testator information regarding the testator, and the public key is stored in a temporary document storage means in association with the testator information regarding the testator. When a request is received to preserve a will-related document with a witness signature, which is an electronic signature of a witness using a key, after confirming the witness signature, the document image data to be saved in the temporary document storage means is stored together with the tamper-proofing means. An encrypted common key is stored in a management storage means, and a predetermined common key is encrypted using a public key, and document image data to be saved is encrypted using a predetermined common key. The method is characterized in that the encrypted common key and the encrypted document image data are stored in an external recording medium, and the encrypted common key stored in the external recording means is decrypted with a private key to extract a predetermined common key.

JP2015-64767A

Conventionally, in order to prove the integrity of an electronic file, an electronic certificate was required as in Patent Document 1. However, when using an electronic certificate, it is necessary to communicate with a certification authority (third party) using a private key and a public key, and certification by the certification authority is required. For this reason, it is necessary to purchase a digital certificate, it is necessary to prepare an infrastructure for communicating with a certificate server (used by a certificate authority) via a network, and it is necessary to set an expiration date on the digital certificate itself. There was a problem that various burdens such as , etc. were incurred.
In view of these circumstances, it is an object of the present invention to reduce the burden of proving the integrity of electronic files.

The present invention that solves the above problems is a tampering detection system that includes a storage unit that stores integrity information in electronic files.

The present invention also provides a calculation unit that calculates original integrity information for the original electronic file;
The tampering detection system includes a storage unit that stores the calculated original integrity information as digital watermark information in the original electronic file.
The present invention also provides a reading unit that reads out the original integrity information from a target electronic file that is the same target as the original electronic file;
It is preferable that the image forming apparatus further includes a comparison section that compares the original integrity information read from the target electronic file and target integrity information calculated for the target electronic file by the calculation section.

Further, the present invention is a recording material in which an electronic file in which integrity information is stored is printed out.

Further, the present invention provides that the tampering detection system
a calculation step of calculating original integrity information for the original electronic file;
The tampering detection method includes a storing step of storing the calculated original integrity information in the original electronic file as digital watermark information.
Further, the present invention provides that the tampering detection system includes:
a reading step of reading out the original integrity information from a target electronic file that is the same target as the original electronic file;
It is preferable to further perform a comparison step of comparing the original integrity information read from the target electronic file with the target integrity information calculated for the target electronic file in the calculation step.

According to the present invention, it is possible to reduce the burden of proving the integrity of an electronic file.

FIG. 1 is a functional configuration diagram of a tampering detection system in a first embodiment. This is a specific example of an electronic file. This is an example of the format of digital watermark information. This is an example of the format of metadata. This is an example of the format of a processing log. FIG. 3 is an explanatory diagram of cases 1 and 2 of tampering verification. It is a flowchart regarding storage of integrity information in a 1st embodiment. It is a flowchart regarding verification of tampering in the first embodiment. It is a flowchart regarding storage of integrity information in a 2nd embodiment. It is a flowchart regarding verification of tampering in the second embodiment.

≪First embodiment≫
[composition]
FIG. 1 is a functional configuration diagram of the tampering detection system in the first embodiment. The tampering detection system 1 is a computer that detects tampering with electronic files. The tampering detection system 1 includes hardware such as an input section, an output section, a control section, and a storage section. For example, when the control section is composed of a CPU (Central Processing Unit), information processing by a computer including the control section is realized by program execution processing by the CPU. Further, a storage unit included in the computer stores various programs for realizing the functions of the computer according to instructions from the CPU. This allows software and hardware to work together. The program can be provided by being recorded on a recording medium or via a network.

The tampering detection system 1 includes a calculation section 11, a storage section 12, a reading section 13, and a comparison section 14. The tampering detection system 1 also stores a processing log DB 15. "DB" is an abbreviation for database (DataBase). The calculation unit 11 calculates integrity information for the electronic file. The electronic file is, for example, a PDF (Portable Document File), but is not limited thereto. Integrity information is information that guarantees that all data is complete and that there are no defects or inconsistencies (integrity). For example, the calculation unit 11 can calculate integrity information by acquiring all objects in an electronic file as a byte array and calculating a checksum.

The storage unit 12 stores integrity information in electronic files. For example, the storage unit 12 can store integrity information as digital watermark information. Furthermore, the storage unit 12 can store integrity information as at least one of electronic file metadata, tint block data, or a processing log associated with a watermark ID. Furthermore, the storage unit 12 can store creation date and time information and creator information of the electronic file. The creation date and time information is information (eg, a timestamp) indicating the timing at which the electronic file was created. The creator information is information indicating the user who created the electronic file. For example, the storage unit 12 can store creation date and time information and creator information as digital watermark information.

The reading unit 13 reads integrity information stored in the electronic file.
The comparison unit 14 compares the integrity information read from the electronic file by the reading unit 13 and the integrity information calculated for the electronic file by the calculation unit 11. The comparison unit 14 determines that the electronic file has not been tampered with if the two pieces of integrity information match, and determines that the electronic file has been tampered with if they do not match.
The processing log DB 15 stores a history of processing contents for electronic files as a processing log. The processing log can be stored in a location different from the electronic file (that is, the processing log DB 15). However, the processing log may be stored in an electronic file.

The tampering detection system 1 can operate the calculation unit 11, storage unit 12, reading unit 13, comparison unit 14, and processing log DB 15 even when offline. However, the tampering detection system 1 can operate the calculation unit 11, storage unit 12, reading unit 13, comparison unit 14, and processing log DB 15 even when online. The processing log DB 15 can be implemented as a built-in storage in the tampering detection system 1 or an external storage.

(Example of storing integrity information)
FIG. 2 is a specific example of an electronic file. The electronic file 2 is a PDF file consisting of two pages of PDF (first page 21 and second page 22) and one tint block image 23. In the electronic file 2, text data and image data are written page by page, and links are provided as appropriate. Specifically, text data T and image data I1 to I3 are written on the first page 21, and a link (not shown) is provided. At the bottom right of the first page 21, a metadata area M is provided. Metadata can be stored in the metadata area M. Even if the electronic file 2 is opened and the first page 21 is viewed, the metadata area M and the metadata may not be viewed. The tint block image 23 can store tint block data in the background. In the electronic file 2, the tint block image 23 can be displayed or hidden.

The storage unit 12 can store integrity information as metadata in the metadata area M in the electronic file 2 . In particular, the integrity information as metadata can be digital watermark information. Note that metadata is rewritable.
Furthermore, the storage unit 12 can store integrity information as tint block data stored in the tint block image 23 in the electronic file 2 . In particular, integrity information as background pattern data can be used as digital watermark information. Note that the tint block data cannot be rewritten.
Furthermore, the storage unit 12 can store integrity information in the processing log of the electronic file 2. Specifically, a watermark ID (Identifier) pointed to (associated with) the integrity information stored in the processing log of the electronic file 2 stored in the processing log DB 15 can be stored in the electronic file 2 . The watermark ID is an identifier of a watermark image (not shown) written in the electronic file 2. The storage unit 12 can store the watermark ID at any position in the electronic file 2 (even within the watermark image), and in particular can store it as electronic watermark information.

(Format of various data)
FIG. 3 is an example of the format of digital watermark information. The example shown in FIG. 3 is an example suitable for use in tampering detection. For example, the digital watermark information format 31 can be only a "watermark ID" (watermark ID stored in the storage unit 12). According to format 31, the amount of digital watermark information can be minimized. Further, the digital watermark information format 31a can be a set of "header" and "watermark ID". By using a "header", you can specify the pattern of the data that follows. Furthermore, by using the "watermark ID", integrity information can be included in the processing log, and integrity information can be managed remotely.

For example, the digital watermark information format 32 may be set to "header", "integrity information" (integrity information stored in the storage section 12), "creation date and time" (creation date and time information stored in the storage section 12), "creation (creator information stored in the storage unit 12). Each element of the format 32 can be associated with each page of the electronic file. For example, each of "integrity information", "creation date and time", and "creator" can be associated with each of the first page 21, second page 22, and tint block image 23 of the electronic file 2 (FIG. 2). By adding "creation date and time" and "creator" to "integrity information", it is possible to improve the cause tracking performance when tampering occurs, and as a result, the accuracy of tampering detection can be improved. can.

Further, for example, the digital watermark information format 33 can be a set of "header", "integrity information", "integrity information", and "integrity information". In other words, digital watermark information can have multiple types of integrity information. For example, the three types of "integrity information" can be respectively integrity information calculated by the calculation unit 11, integrity information stored as metadata, and integrity information stored as a processing log. At this time, the integrity information stored as tint block data can be designed to be used for purposes other than tampering detection; for example, it can be used for verifying watermark information. Further, each element of the format 33 can be associated in units of pages of the electronic file. For example, each of the three types of "integrity information" can be associated with the first page 21, the second page 22, and the tint block image 23 of the electronic file 2 (FIG. 2).

For example, the digital watermark information format 34 may be set as a set of "header", "integrity information", "creation date and time", "creator", and "location information in the file" (e.g. two-dimensional coordinates of the electronic file). can do. Each element of the format 34 can be associated with each page of the electronic file. For example, "integrity information", "creation date and time", and "creator" can be associated with each of the first page 21, second page 22, and tint block image 23 of the electronic file 2 (FIG. 2), and " "in-file position information" can be associated with the first page 21 of the electronic file 2 (FIG. 2). Elements of two or more formats may be associated with one page.

Digital watermark information in formats 31 to 34 can be selected as appropriate depending on the content of the electronic file.
Regarding the digital watermark information in format 31, the reading unit 13 can recognize the watermark ID by analyzing the value of the watermark ID itself, depending on the uniqueness of the "watermark ID." Furthermore, regarding digital watermark information in formats 31a, 32 to 34, by analyzing the "header" value itself, the pattern of the following data can be recognized as digital watermark information.

FIG. 4 is an example of the format of metadata. The example shown in FIG. 4 is an example suitable for use in tampering detection. For example, the metadata format 40 can be a set of "creation date and time", "creator", and "integrity information". By adding "creation date and time" and "creator" to "integrity information", it is possible to improve the cause tracking performance when tampering occurs, and as a result, the accuracy of tampering detection can be improved. can.
Since the reading unit 13 understands the data structure of the metadata, it can recognize creation date and time information, creator information, and integrity information stored in the metadata.

FIG. 5 is an example of the format of a processing log. The example shown in FIG. 5 is an example suitable for use in tampering detection. For example, the format 50 of the processing log can be a set of "watermark ID", "creation date and time", "creator", and "integrity information". In this case, the "watermark ID" can be used as a search key for the processing log for extracting the "integrity information". By adding "watermark ID", "creation date and time", and "creator" to "integrity information", it is possible to remotely manage integrity information and improve the ability to trace the cause in the event of falsification. Therefore, it is possible to improve the tampering detection accuracy as a result. Further, the format 50a of the processing log can be a set of "creation date and time", "creator", and "integrity information". In this case, at least one of the "creation date and time" and the "creator" can be used as a processing log search key for extracting the "integrity information".
Since the reading unit 13 understands the data structure of the processing log, it can recognize the watermark ID, creation date and time information, creator information, and integrity information stored in the processing log.

(Tampering verification example)
<Case 1>
FIG. 6 is an explanatory diagram of cases 1 and 2 of tampering verification. Case 1 shows a case where tampering is verified at the destination where the PDF file is circulated. The tampering detection system 1A(1) used by user A can write (storage) integrity information as digital watermark information, for example, as metadata when creating the original PDF 61 (circulation source PDF file). Further, the tampering detection system 1A can write (store) integrity information as digital watermark information in the processing log 62. The tampering detection system 1A(1) can send an email with the original PDF 61 attached to the tampering detection system 1B(1) used by user B.

The tampering detection system 1B sets the original PDF 61 attached to the email received from the tampering detection system 1A as the PDF 63 to be tampered with, and verifies whether or not the PDF 63 has been tampered with. The tampering detection system 1B determines whether the integrity information calculated for the PDF63 matches the integrity information written in the metadata of the PDF63 (the same integrity information written in the metadata of the original PDF61). By determining whether or not the data has been tampered with, it is possible to determine whether or not it has been tampered with. For example, it is possible to detect tampering, such as when a third party stealthily viewed an e-mail sent to the tampering detection system 1B(1) and rewritten the contents of the original PDF 61 attached to the e-mail.

<Case 2>
Case 2 shows a case where tampering is verified at the source of the PDF file. The tampering detection system 1A(1) used by user A can write (storage) integrity information as digital watermark information, for example, as metadata when creating the original PDF 61 (circulation source PDF file). Further, the tampering detection system 1A can write (store) integrity information as digital watermark information in the processing log 62. The tampering detection system 1A can send an e-mail or the like with the original PDF 61 attached to the tampering detection system 1B(1) used by user B.

The tampering detection system 1B acquires the original PDF 61 attached to the email received from the tampering detection system 1A as a PDF 64. When user B refers to the PDF 64, the tampering detection system 1B can send an e-mail or the like with the PDF 64 attached to the tampering detection system 1A.

The tampering detection system 1A sets the PDF 64 attached to the email received from the tampering detection system 1B as a returned PDF 65 to be verified for tampering, and verifies whether or not the returned PDF 65 has been tampered with. The tampering detection system 1A determines that the integrity information calculated for the returned PDF 65 matches the integrity information written in the metadata of the returned PDF 65 (same as the integrity information written in the metadata of the original PDF 61). By determining whether or not the data has been tampered with, it is possible to determine whether or not it has been tampered with. For example, it is possible to detect tampering such as when user B of the tampering detection system 1B(1) rewrites the contents of PDF64.

[process]
Next, the processing of the tampering detection method will be explained. FIG. 7 is a flowchart regarding storage of integrity information in the first embodiment. In the first embodiment, processing is performed using digital watermark information of format 31 (FIG. 3). The following processing is performed on the created electronic file (hereinafter sometimes referred to as "original electronic file"). First, the calculation unit 11 of the tampering detection system 1 calculates integrity information of the original electronic file (step A1). Next, the tampering detection system 1 generates a watermark ID (step A2). Note that the method for generating the watermark ID is well known, and the details will be omitted. Next, the storage unit 12 of the tampering detection system 1 stores the generated watermark ID in the original electronic file (step A3). For example, the storage unit 12 can store a watermark ID in a tint block image written in the original electronic file. Next, the storage unit 12 of the tampering detection system 1 stores the creation date and time information, creator information, and integrity information of the original electronic file as metadata (step A4). Therefore, creation date and time information, creator information, and integrity information are stored in the metadata area of the original electronic file. Next, the storage unit 12 of the tampering detection system 1 stores the watermark ID, creation date and time information, creator information, and integrity information of the original electronic file as a processing log (step A5). The processing log is stored in the processing log DB 15. With this, the process in FIG. 7 is completed. Note that the storage unit 12 may store the watermark ID, creation date and time information, creator information, and integrity information of the original electronic file as tint block data.

FIG. 8 is a flowchart regarding verification of tampering in the first embodiment. When verifying whether or not a circulated original electronic file (hereinafter sometimes referred to as a "target electronic file") has been tampered with, the following process is executed. First, the tampering detection system 1 specifies a target electronic file according to input from the user (step B1). Next, the calculation unit 11 of the tampering detection system 1 calculates the integrity information of the target electronic file (step B2). Next, the reading unit 13 of the tampering detection system 1 reads integrity information from the metadata of the target electronic file (step B3). Next, the reading unit 13 of the tampering detection system 1 reads the watermark ID from the target electronic file (step B4). The watermark ID read out is the watermark ID stored in the original electronic file. Next, the reading unit 13 of the tampering detection system 1 searches for a processing log associated with the read watermark ID (step B5). Specifically, a search is performed on the processing log DB 15 using the watermark ID as a search key.

If the search is successful (Yes in step B6), the reading unit 13 of the tampering detection system 1 reads integrity information from the extracted processing log (step B7). Next, the comparison unit 14 of the tampering detection system 1 compares the three types of integrity information (step B8). Specifically, the comparison unit 14 compares the integrity information calculated in step B2, the integrity information read from the metadata in step B3, and the integrity information read from the processing log in step B7. Compare. If the three types of integrity information match (Yes in step B9), the comparison unit 14 determines that the target electronic file has not been tampered with (step B10), and ends the process. On the other hand, if the three types of integrity information do not match (No in step B9), the comparison unit 14 determines that the target electronic file has been tampered with (step B12), and ends the process. In addition, "the target electronic file has been tampered with" basically means that the checksum indicating the integrity information calculated for the target electronic file is not the same as the checksum indicating the integrity information calculated for the original electronic file. It means something different.

On the other hand, if the search is not successful (No in step B6), the comparison unit 14 of the tampering detection system 1 compares the two types of integrity information (step B11). Specifically, the comparison unit 14 compares the integrity information calculated in step B2 and the integrity information read from the metadata in step B3. If the two types of integrity information match (Yes in step B9), the comparison unit 14 determines that the target electronic file has not been tampered with (step B10), and ends the process. At this time, it is preferable that the tampering detection system 1 displays a warning indicating that the search was not successful and the integrity information of the processing log could not be read. On the other hand, if the two types of integrity information do not match (No in step B9), the comparison unit 14 determines that the target electronic file has been tampered with (step B12), and ends the process. At this time, the tampering detection system 1 may display a warning that the search was not successful and the integrity information of the processing log could not be read.

(recording material)
When the output unit of the tampering detection system 1 has a printing function, the output unit can print out an electronic file storing integrity information as digital watermark information. A printed document on a paper medium (recording material) includes integrity information printed with a watermark. If the input unit of the tampering detection system 1 has a scanning function, when a document is circulated, the input unit can scan the circulated document to verify whether or not it has been tampered with. The processing procedure for verifying the presence or absence of tampering can be the same as the one already described. Note that if the circulated document is dirty or torn, the tampering detection system 1 can acquire integrity information by reading tint block data from the document and use it to verify whether or not it has been tampered with.

According to the first embodiment, since the integrity information is stored in the electronic file, it is possible to prove the integrity of the electronic file without creating an electronic certificate which is a separate medium from the electronic file. Therefore, there is no need to have a certification authority create an electronic certificate, that is, there is no need for certification by a certification authority. Moreover, there is no need to purchase an electronic certificate, and there is no need to bear the cost of purchasing an electronic certificate. Furthermore, there is no need to prepare an infrastructure for communicating with a certificate server (used by a certificate authority) via a network, and there is no need to bear infrastructure installation costs. Furthermore, compared to the conventional method in which a time limit must be set on an electronic certificate, there is no need to set a time limit on the electronic file of the present invention that allows integrity information. Therefore, there is no need to bear additional costs and efforts such as reissuing electronic certificates. Therefore, the burden of proving the integrity of electronic files can be reduced.
Furthermore, in the past, electronic certificates were basically obtained on a company-by-company basis, which was suitable for exchanging electronic documents with outside the company, but unsuitable for exchanging electronic documents within the company. Furthermore, conventionally, the number of man-hours required to construct a system for operating electronic certificates was enormous. In contrast, the functions of the tampering detection system of the present invention can be installed in the computers used by each employee and can be used individually, making it suitable for exchanging electronic documents within the company. Furthermore, the number of man-hours required for system construction can be reduced.
Further, the tampering detection system of the present invention can execute processing related to verifying whether or not an electronic file has been tampered with within one computer, and can operate offline.

Further, by using digital watermark information as the integrity information, it is possible to reduce the possibility of tampering with the integrity information, and as a result, it is possible to improve the accuracy of tampering detection of the electronic file that stores the integrity information.
Furthermore, by storing the creation date/time information and creator information of the electronic file, it is possible to improve the cause tracking performance when tampering occurs, and as a result, the accuracy of tampering detection can be improved.
Additionally, since integrity information can be stored in metadata, tint block data, or processing logs associated with watermark IDs, many options for proving the integrity of electronic files can be provided. In particular, when the integrity information is stored in a processing log, the integrity information can be monitored remotely and the possibility of tampering with the integrity information can be extremely reduced.
Furthermore, by providing the calculation section 11 and the storage section 12, the integrity of the original electronic file can be easily verified.
Further, by providing the reading unit 13 and the comparison unit 14, it is possible to easily verify whether or not a target electronic file that is the same as the original electronic file has been tampered with.
In addition, the first integrity information calculated for the target electronic file, the second integrity information stored as metadata of the target electronic file, and the processing log associated with the watermark ID of the target electronic file are stored. By comparing the third integrity information with the third integrity information, the accuracy of detecting tampering with the target electronic file can be greatly improved.
Further, a recording material obtained by printing out an electronic file in which integrity information is stored can prove extremely high integrity, similar to the electronic file in which integrity information is stored.

≪Second embodiment≫
When describing the second embodiment, the differences from the first embodiment will be explained, and the explanation of the overlapping points will basically be omitted. In the second embodiment, processing is performed using digital watermark information of format 32 (FIG. 3). FIG. 9 is a flowchart regarding storage of integrity information in the second embodiment. The following processing is performed on the created original electronic file. First, the calculation unit 11 of the tampering detection system 1 calculates integrity information of the original electronic file (step C1). Next, the tampering detection system 1 generates digital watermark information (step C2). The digital watermark information includes a header, creation date and time information, creator information, and integrity information. Note that the method for generating digital watermark information is well known, and the details will be omitted. Next, the storage unit 12 of the tampering detection system 1 stores the generated digital watermark information in the original digital file (step C3). For example, the storage unit 12 can store digital watermark information in a tint block image written in the original electronic file. Next, the storage unit 12 of the tampering detection system 1 stores the creation date and time information, creator information, and integrity information of the original electronic file as metadata (step C4). Therefore, creation date and time information, creator information, and integrity information are stored in the metadata area of the original electronic file. Next, the storage unit 12 of the tampering detection system 1 stores the creation date and time information, creator information, and integrity information of the original electronic file as a processing log (step C5). The processing log is stored in the processing log DB 15. With this, the process in FIG. 9 ends. Note that the storage unit 12 may store creation date and time information, creator information, and integrity information of the original electronic file as tint block data.

FIG. 10 is a flowchart regarding verification of tampering in the second embodiment. When verifying whether or not the target electronic file has been tampered with, the following processing is executed. First, the tampering detection system 1 specifies a target electronic file according to the input from the user (step D1). Next, the calculation unit 11 of the tampering detection system 1 calculates the integrity information of the target electronic file (step D2). Next, the reading unit 13 of the tampering detection system 1 reads integrity information from the metadata of the target electronic file (step D3). Next, the reading unit 13 of the tampering detection system 1 reads creation date and time information and creator information from the target electronic file (step D4). The creation date and time information and creator information that are read are the creation date and time information and creator information stored in the original electronic file. Next, the reading unit 13 of the tampering detection system 1 searches the processing log associated with the read creation date and time information and creator information (step D5). Specifically, a search is performed on the processing log DB 15 using the creation date and time information and creator information as search keys.

If the search is successful (Yes in step D6), the reading unit 13 of the tampering detection system 1 reads integrity information from the extracted processing log (step D7). Next, the comparison unit 14 of the tampering detection system 1 compares the three types of integrity information (step D8). Specifically, the comparison unit 14 compares the integrity information calculated in step D2, the integrity information read from the metadata in step D3, and the integrity information read from the processing log in step D7. Compare. If the three types of integrity information match (Yes in step D9), the comparison unit 14 determines that the target electronic file has not been tampered with (step D10), and ends the process. On the other hand, if the three types of integrity information do not match (No in step D9), the comparison unit 14 determines that the target electronic file has been tampered with (step D11), and ends the process.

On the other hand, if the search is not successful (No in step D6), the comparison unit 14 determines that the target electronic file has been tampered with (step D11), and ends the process. At this time, the tampering detection system 1 may display a warning that the search was not successful and the integrity information of the processing log could not be read.
According to the second embodiment, the same effects as the first embodiment are achieved.

[Modified example]
(a): The integrity information stored in the electronic file does not have to be electronic watermark information.
(b): The recording material is not limited to paper, and the present invention can be applied to various materials such as cloth, laminate, and resin.
(c): In the first embodiment, if the search is not successful (No in step B6), instead of comparing two types of integrity information (step B11), it may be determined that tampering has occurred ( Step B12).
(d): In the second embodiment, if the search is not successful (No in step D6), two types of integrity information (integrity information calculated in step D2 and read out from the metadata in step D3) integrity information) may be compared. If the two types of integrity information match, the comparison unit 14 may determine that the target electronic file has not been tampered with. At this time, it is preferable that the tampering detection system 1 displays a warning indicating that the search was not successful and the integrity information of the processing log could not be read. On the other hand, if the two types of integrity information do not match, the comparison unit 14 may determine that the target electronic file has been tampered with.
(e): In the first and second embodiments, the tampering detection system 1 includes a calculation section 11, a storage section 12, a reading section 13, and a comparison section 14, and stores a processing log DB 15. It was configured so that However, for example, first software that implements the calculation unit 11 and storage unit 12 and second software that implements the calculation unit 11, readout unit 13, and comparison unit 14 are prepared and introduced into the tampering detection system 1, respectively. You can. The tampering detection system 1 may be divided into a first and second system, and the first software may be introduced into the first tampering detection system, and the second software may be introduced into the second tampering detection system. The processing log DB 15 may be stored in a storage separate from the tampering detection system 1. The processing log DB 15 stored in the storage may be implemented so that it can be shared by a plurality of computers having the same functions as the tampering detection system 1. The processing log DB 15 stored by the tampering detection system 1 may also be implemented so that it can be shared by a plurality of computers separate from the tampering detection system 1.

(f): It is also possible to realize a technique that combines the various techniques described in this embodiment as appropriate.
(g): The software described in this embodiment can be implemented as hardware, and the hardware can also be implemented as software.
(h): Other changes may be made as appropriate to the hardware, software, flowcharts, etc. without departing from the spirit of the present invention.

1 Tampering detection system 11 Calculation unit 12 Storage unit 13 Reading unit 14 Comparison unit 15 Processing log DB

Claims (4)

a calculation unit that calculates original integrity information for the original electronic file;
a storage unit that stores the calculated original integrity information in the original electronic file as digital watermark information ,
a reading unit that reads out the original integrity information from a target electronic file that is the same target as the original electronic file;
further comprising a comparison unit that compares the original integrity information read from the target electronic file and target integrity information calculated by the calculation unit for the target electronic file,
The target integrity information is first integrity information calculated by the calculation unit for the target electronic file,
The original integrity information read from the target electronic file is stored as second integrity information stored as metadata of the target electronic file, and second integrity information stored as a processing log associated with a watermark ID of the target electronic file. 3 completeness information,
The comparison unit is a tampering detection system that compares the first integrity information, the second integrity information, and the third integrity information. The tampering detection system according to claim 1 , wherein the storage unit further stores creation date and time information and creator information of the original electronic file. 3. The tampering detection system according to claim 1, wherein the original integrity information is stored as at least one of metadata, tint block data, or a processing log associated with a watermark ID. The tampering detection system
a calculation step of calculating original integrity information for the original electronic file;
storing the calculated original integrity information in the original electronic file as digital watermark information ;
The tampering detection system
a reading step of reading out the original integrity information from a target electronic file that is the same target as the original electronic file;
further performing a comparison step of comparing the original integrity information read from the target electronic file with the target integrity information calculated for the target electronic file in the calculation step;
The target integrity information is first integrity information calculated for the target electronic file in the calculation step,
The original integrity information read from the target electronic file is stored as second integrity information stored as metadata of the target electronic file, and second integrity information stored as a processing log associated with a watermark ID of the target electronic file. 3 completeness information,
The tampering detection method includes, in the comparison step, comparing the first integrity information, the second integrity information, and the third integrity information.

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