JP3948964B2 - Electronic document processing apparatus and computer program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to processing of an electronic document by an electronic computer, and more particularly to an electronic document management and information guarantee method.
[0002]
[Prior art]
In recent years, many documents and documents have been distributed as electronic documents. In general, electronic documents can be updated or corrected (hereinafter referred to as “update”) relatively frequently. For example, for one electronic document, users in different positions may circulate the electronic document, and each person may update the electronic document. In such a case, an unspecified number of update operations are performed on one electronic document.
[0003]
[Problems to be solved by the invention]
However, no matter how many times it is updated, generally only the latest generation of electronic documents is stored. Therefore, it is impossible to restore the state of each generation of electronic documents that has been updated from the electronic document alone. Therefore, in the distribution of electronic documents, who has made any updates on the electronic documents in the past. It was difficult to grasp exactly.
[0004]
On the other hand, in order to grasp the status of the electronic document of each updated generation, it is only necessary to save and save all the updated versions of the electronic document in each generation. This may include redundant parts that are not used, and waste storage capacity for data storage. Further, it becomes necessary to organize and store document data of a plurality of generations for the same electronic document, and management becomes complicated.
[0005]
In addition, when an author or an updater attaches an electronic signature to an electronic document to guarantee the content, if the content of the electronic document itself is updated, the update of the previous generation is updated. The electronic signature attached in step cannot be verified. That is, in a certain generation, an electronic signature is attached to the updated document content and stored, but if the document content is further changed due to the update in the next generation, an electronic signature for the previous generation is created. Since the target document content itself does not exist, it is not possible to verify the digital signature attached in that generation. Therefore, when updates are made over a plurality of generations, it becomes impossible to verify the electronic signatures attached in the past update generations, and eventually the meaning of attaching the electronic signatures is lost. As a result, it is a serious security problem that it is not possible to check whether the document content update in the past update generation has been made by a legitimate modification or whether it has been falsified by malicious intent by verifying the electronic signature. As a result, it has been difficult to guarantee information on electronic documents.
[0006]
The present invention has been made in view of the above points, and restores the document content in each generation of an electronic document updated multiple times, and correctly verifies the electronic signature attached in that generation. It is an object to realize reliable information assurance of electronic documents.
[0007]
[Means for Solving the Problems]
  In one aspect of the present invention, in an electronic document processing apparatus, a document processing unit for creating or updating an electronic document, and a history of updates performed on the electronic document are extracted through the document processing unit. Update history creation means for storing the update history information in association with the electronic document.The update history information includes difference information between the electronic document before update and the electronic document after update, and an electronic signature created using the difference information as target data.
[0008]
According to the electronic document processing apparatus, the user creates a new electronic document or updates an already created electronic document. When the user updates the electronic document by changing or correcting the content of the electronic document, the update history is extracted and stored as update history information in association with the electronic document. Therefore, by referring to the update history information, it is possible to restore the electronic document before and after the past update.
[0010]
  In one aspect of the electronic document processing apparatus, the update history information is created for each update operation, and the update history information indicates how many times the update operation is performed on the electronic document. Generation information can be included. Thereby, it is possible to perform restoration so as to go back to the target generation using the update history information.
[0011]
In still another aspect of the electronic document processing apparatus, the update history creating unit may include the update history information in the electronic document as information separate from text data of the electronic document.
[0012]
In still another aspect of the electronic document processing apparatus, the document processing unit stores the updated electronic document as body data, and uses the updated electronic document as the target data. It can be stored in electronic documents.
[0013]
In another aspect of the present invention, in an electronic document processing apparatus, an electronic document is created by an update operation based on display means for reading and displaying an electronic document, the electronic document, and update history information related to the electronic document And a document restoring means for restoring the past generation electronic document.
[0014]
  According to the above electronic document processing apparatus, the user reads an electronic document that has already been created and has been updated several times. Then, a past generation electronic document is restored using the electronic document and the update history information.The update history information includes difference information between the electronic document before update and the electronic document after update, and an electronic signature created using the difference information as target data, and the document restoration means includes the history guarantee The electronic document is restored only when verification of the electronic signature is successful. According to this, restoration of the electronic document is executed only when the stored difference information is correct.
[0015]
In one aspect of the electronic document processing apparatus, the electronic document includes an electronic signature created using the updated electronic document as target data, and the document restoration unit uses the restored electronic document to generate the generation. Verification means for verifying an electronic signature corresponding to the electronic document. Thus, in addition to restoring and confirming the contents of the electronic document of a specific generation, it can be confirmed by verifying the electronic signature whether or not the update processing of that generation has been performed properly.
[0017]
In still another aspect of the electronic document processing apparatus, the electronic document processing apparatus further includes designation means for inputting designation of the generation of the electronic document to be restored, wherein the document restoration means includes the generation of electronic data designated by the designation means. Restore the document. According to this aspect, the digital signature of the generation designated by the user can be restored.
[0018]
  In still another aspect of the present invention, the computer program extracts a history of updates made to the electronic document through the document processing means for creating or updating the electronic document and the document processing means. Then, the computer is caused to function as an electronic document processing apparatus including update history creation means for storing the update history information in association with the electronic document.The update history information includes difference information between the electronic document before update and the electronic document after update, and an electronic signature created using the difference information as target data.
[0019]
  In still another aspect of the present invention, the computer program performs an update operation based on display means for reading and displaying an electronic document, the electronic document, and update history information related to the electronic document. A computer is caused to function as an electronic document processing apparatus comprising: a document restoring unit that restores a created past generation electronic document.The update history information includes difference information between the electronic document before update and the electronic document after update, and an electronic signature created using the difference information as target data, and the document restoration means includes the history guarantee The electronic document is restored only when verification of the electronic signature is successful.
[0020]
By executing the above computer program on a computer such as a terminal device or a server device, the computer can be caused to function as the above-described electronic document processing device. Similarly, the various aspects described above can also be employed.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings.
[0022]
[Electronic document processing device]
The electronic document processing apparatus of the present invention is realized by executing a program to be described later in a terminal device for processing an electronic document, such as a personal computer or a server device installed in an individual user's house or company. .
[0023]
As an environment for using electronic documents, for example, when users create application forms, application forms, and other various electronic documents to be submitted to government offices or companies, and submit them to government offices or companies using a network such as the Internet. Can be considered. At that time, the user can create or update a necessary electronic document on a computer or terminal device installed at home or work. In addition, on the government office or company side, an electronic document received via a network can be restored in a server device or a terminal device, and an electronic signature can be verified.
[0024]
The electronic document processing apparatus of the present invention can perform document update processing and document restoration processing in addition to creating an electronic document from the beginning. The document update process is a process for storing an update history of an electronic document, and an outline thereof is shown in FIG. The user executes the electronic document processing program 7 using a terminal device or the like. As a basic function, the electronic document processing program 7 includes an update history creation function 10 in addition to a browser function 8 for browsing an electronic document and a document creation function 9 for a user to input necessary items. Prepare.
[0025]
As shown conceptually in FIG. 1A, the update history creation function 10 is updated when a user updates an electronic document 20 that has already been created (that is, changes, modifications, etc. of document contents). The history information 25 is created, attached to the electronic document 20, or included in the electronic document 20 and stored. Specifically, when the user executes the electronic document processing program 7 to read an existing electronic document 20 and makes necessary changes or corrections, the electronic document 20 after the change is saved and the changed changes are made. Update history information 25 indicating the contents and the like is created. Then, the update history information 25 is stored in the electronic document 20 in association with the electronic document 20 by incorporating it into the electronic document 20 or by integrating it with the electronic document 20 on data.
[0026]
On the other hand, the document restoration process is a process for restoring an electronic document in a state before the update is performed by using the update history information 25 created by the document update process, and an outline thereof is shown in FIG. . The user executes the electronic document processing program 11 using a terminal device or the like. The electronic document processing program 11 includes, as basic functions, a browser function 12 for browsing an electronic document, a document creation function 13 for a user to input necessary items, and an electronic document restoration function 15. Prepare.
[0027]
As shown in FIG. 1B, the electronic document restoration function 15 uses the update history information 25 to restore the electronic document 20 in a state before being updated. Specifically, the user executes the electronic document processing program 11 to read an existing electronic document 20, and based on the electronic document 20 and the update history information 25 attached thereto, the electronic document 20 in an unupdated state is displayed. Restore.
[0028]
[Structure of electronic document]
Next, the electronic document and the update history information will be described in detail. FIG. 2 shows an example of the data structure of the electronic document 20. The electronic document 20 includes a body 21, one or more electronic signatures 22, and update history information 25. The body 21 is a part corresponding to the contents of the electronic document 20. For example, when the electronic document 20 is a predetermined report, the description of the report content in the report is included in the text 21.
[0029]
The electronic signature 22 is used to clearly indicate that the creator of the electronic document 20 and the person who performed the update work (referred to as “update worker”) are responsible for the contents created or updated by the person. Attached. Specifically, first, the creator of the electronic document 20 attaches the electronic signature 22, and thereafter, the electronic signature 22 by the update operator is added each time an update is made. In this way, electronic signatures 22 are added by the number of update operations performed.
[0030]
The update history information 25 includes an update record 26 created for each update process performed on the electronic document 20. That is, when the electronic document 20 is updated n times, n update records 26 from the first generation to the nth generation are included in the update history information 25.
[0031]
Each generation update record 26 includes update difference information 27 and a history guarantee signature 28. Here, the update difference information 27 is information indicating a difference between the content of the text 21 before the update and the content of the text 21 after the update. As actual data, the data of the text 21 before the update and the data after the update are updated. This is the difference data from the data in the main text 21.
[0032]
The resume guarantee signature 28 is a signature that is created for each update generation and has a meaning of guaranteeing that the update difference information 27 created by the update processing of that generation has not been falsified. This is an electronic signature created based on the update difference information 27 created at the time.
[0033]
Therefore, in FIG. 2, there are two types of electronic signatures, that is, the electronic signature 22 and the history guarantee signature 28, but they are different. The electronic signature 22 has a meaning of guaranteeing the content of the updated text 21 when a certain update operator performs a predetermined update operation on the text 21, and specifically, the updated text. 21 is created as signature target data (data to be used for creating an electronic signature). On the other hand, the history guarantee signature 28 has a meaning that the update operator guarantees the contents of the update difference information 27 created in the update work of the generation. Is created as signature target data.
[0034]
[Electronic signature]
Next, in order to facilitate understanding of the present application, the electronic signature will be briefly described. The electronic signature is a technique for guaranteeing the contents of data by making it possible to detect falsification of a document or other data to be protected. The electronic signature is given by specifying signature target data. For example, in the case of a public key cryptosystem, creation of an electronic signature is performed by calculating a hash value of data to be signed and encrypting the obtained hash value with a secret key possessed by the signer. The electronic signature is data itself obtained by such encryption. Since the private key is possessed only by the signer, the created electronic signature is data that depends on the private key. The electronic signature obtained in this way is generally provided to a third party who performs verification together with the signature target data.
[0035]
On the other hand, the third party who acquired the signature target data and the electronic signature calculates a hash value of the signature target data. Also, the digital signature is decrypted with the signer's public key to obtain a hash value, and is compared with the hash value calculated from the signature target data. If the two match, it can be seen that the obtained signature target data has not been tampered with. Conversely, when the signature target data passed to a third party has been tampered with, the hash value calculated from the signature target data does not match the hash value obtained by decrypting the electronic signature. In this way, the electronic signature is verified.
[0036]
Thus, an electronic signature cannot be verified without the signature target data of the electronic signature. Therefore, in the document restoration process of the present invention, when investigating the suitability of update work in any past generation, the electronic document of the target generation is restored using the update difference information 27 in the update history information 25, Using it, the digital signature in that generation is verified.
[0037]
[Document update processing]
Next, the flow of document update processing will be described with reference to FIG. FIG. 3 is a flowchart of the document update process. When the document update process is executed, it is assumed that an already created electronic document 20 exists. Further, in order to execute the document update process, the user executes the electronic document processing program shown in FIG.
[0038]
First, a user who updates the electronic document 20 executes an electronic document processing program in the terminal device, and reads the electronic document 20 to be updated using the browser function 8 and the document creation function 9 (step S1). Then, necessary editing such as addition and deletion is performed on the body 21 in the electronic document 20 (step S2).
[0039]
When the editing work by the user is completed, the update history creation function 10 of the electronic document processing program 7 operates to extract the difference data of the text 21 before and after the update and temporarily store it as the update difference information 27 (step S3). ).
[0040]
Next, the update history creation function 10 uses the updated text 21 as signature target data, creates an electronic signature 22 using the update operator's private key, and includes it in the electronic document 20 (step S4). Further, the history difference signature 27 is created using the update difference information 27 created in step S3 as signature target data and using the secret key of the update operator (step S5).
[0041]
Finally, the update difference information 27 and the history guarantee signature 28 are collected to form an update record 26 for that generation, and included in the electronic document 20 (step S6). Thus, one update operation is completed, and the corresponding update record 26 is included in the electronic document 20 as update history information 25. Thereafter, when the update work is repeatedly performed, an update record 26 including the update difference information 27 and the history guarantee signature 28 is created every time the update work is performed, and is added to the electronic document 20 as a part of the update history information 25.
[0042]
[Document restoration processing]
Next, the document restoration process will be described with reference to FIGS. Now, it is necessary to investigate an update operation before n generations, and an electronic signature before n generations is verified. In order to verify the electronic signature of n generations before, the state of the electronic document of n generations before must be restored. Therefore, using the current electronic document 20a and the update history information 25, the electronic document 20 is restored retroactively to the previous n generations.
[0043]
Specifically, as shown in FIG. 4, first, update difference information 27 is obtained from the update record 26 one generation before. Since the update difference information 27 is difference data of the electronic document before and after the update made in that generation, the electronic document 20b of the previous generation is restored by the body 21 and the update difference information 27 of the current electronic document 20a. .
[0044]
Next, the update difference information 27 is acquired from the update record 26 two generations before, and the electronic document 20 c two generations before is restored by using the update difference information 27 and the body 21 of the electronic document 20 b one generation before. By repeating this process, the electronic document 20n before n generations is restored. Thus, when the electronic document 20n before n generations can be restored, the electronic signature 22 before n generations can be verified based on the restoration.
[0045]
Next, the flow of document restoration processing will be described with reference to FIG. FIG. 5 is a flowchart of the document restoration process. When the document restoration process is executed, it is assumed that there are already several updated electronic documents 20. In order to execute the document restoration process, the user executes the electronic document processing program 11 shown in FIG.
[0046]
First, a user who restores the electronic document 20 of the nth generation executes the electronic document processing program 11 in the terminal device, and reads the electronic document 20 to be restored using the browser function 8 and the document creation function 9. (Step S11). Next, the following processing is performed by executing the electronic document restoration function 15. That is, the update guarantee signature 28 is extracted from the update record 26 one generation before and verified (step S12). This verification is performed by comparing the hash value calculated from the update difference information 27 of the previous generation and the hash value obtained by decrypting the history assurance signature 28 with the public key of the update operator of that generation. . Thus, when the verification of the history guarantee signature 28 is completed, the update difference information of the previous generation is acquired (step S13), and the electronic data of the previous generation is obtained based on the body 21 of the electronic document 20 and the update difference information of the previous generation. The document 20 is restored (step S14).
[0047]
Next, it is determined whether or not the electronic document obtained in this way is a target electronic document n generations before (step S15). In this example, since the electronic document of n generations before has not been obtained yet, the process returns to step S12, and the processes of steps S12 to S14 are executed using the update record 26 of the previous generation. In this way, the processes in steps S12 to S14 are repeatedly executed until the target electronic document n generations before is restored.
[0048]
When the electronic document 20 before the n generation is restored (step S15; Yes), the electronic signature before the n generation is verified (step S16). That is, the hash value of the restored electronic document before n generations is calculated, and the hash value is calculated by extracting and decrypting the electronic signature 22 before n generations from the electronic document 20, and the two are compared. If they match, it can be seen that the update process n generations before is valid.
[0049]
When verifying the electronic signature by restoring the electronic document in this way, it is desirable to verify all the electronic signatures before the restored generation. This is because even if verification of a digital signature of a generation succeeds, it cannot be said that an electronic signature given before that generation is correct.
[0050]
For example, assuming that an electronic signature that has been updated for five generations is to verify an electronic signature three generations before, first, the electronic signature of the target generation (that is, three generations prior) is first obtained by the above-described procedure. Next, the electronic signature three generations before is verified using the restored electronic document. If this verification succeeds, the electronic signature of the fourth generation before is verified, and if successful, the electronic signature of the fifth generation before is verified. Thus, by successfully verifying all the electronic signatures from the 3rd generation to the 5th generation, it is possible to ensure that the 3rd generation electronic document has not been tampered with.
[0051]
In the example of FIG. 5, the history assurance signature is verified in step S12 and then the restoration processing in steps S13 to S14 is executed. However, verification of the history assurance signature in step S12 may be omitted.
[0052]
[Example]
Next, an example of an electronic document and update history information will be described. FIG. 6 is an example of the update record 26. In this example, the electronic document 20 is configured as an XML document. Therefore, not only the text 21 but also the electronic signature and the update history information 25 are described by the XML document.
[0053]
FIG. 6 is an example of an update record 26 for a generation. In an XML document, document contents are described in a state sandwiched between a start tag indicated by <> and an end tag indicated by </>.
[0054]
In the example of FIG. 6, the portion between <Generation Seq = "1"> and </ Generation> is one generation update record. Also, the portion between <Actions Id “Act_1”> and </ Actions> is the update difference information 27, and the portion of <dsig: ....> on the second line from the bottom is the history assurance signature 28.
[0055]
The update difference information 27 is described in one minute in which one update operation is sandwiched between tags <Update> and </ Update>, as shown in a description example 27a in FIG. Specifically, as shown in the example 27a shown outside the column, the parent node (ParentNode, in this example, <xxx Id = "target_1" />) of the node whose document content is to be changed is specified, and before the update Is indicated by tags <before> and </ before>, and the updated state is indicated by tags <after> and </ after>. The update difference information 27 records the pre-update state and the post-update state in the electronic document based on this description. If there are multiple update locations, the number of descriptions between <Update> and </ Update> is included.
[0056]
Here, the node refers to a portion surrounded by tags in the XML document. When tags are nested, the nodes are configured in a tree structure. FIG. 7 shows the relationship between nodes and data update in the XML document. For example, in the example 70 of “deletion of data” shown in the upper left of FIG. 7, when the node 70b (<aaa Id = “a” />) indicated by a black circle is deleted, the description 70a is created as update difference information. . In the description 70a, the parent node of the node 70b to be deleted (in this example, <xxx Id = "target_1" />) is specified, the state before update is described with tags <before> and </ before>, and the tag < The state after update is described in after> and </ after>.
[0057]
On the other hand, in the “add data” example 71 shown in the upper right of FIG. 7, a node 71b (<bbb Id = “b” shown below the parent node (<xxx Id = “target_1” /> in this example) "/>) Has been added. The description at that time is as shown in description example 71a. Also, as shown in the description example 72, when the node (<aaa Id = "a" />) is deleted and the node (<bbb Id = "b" />) is added, the description in the update difference information 27 Is a description example 72b in which a data deletion example 70 and a data addition example 71 are combined.
[0058]
Description examples of the electronic document before and after the update are shown in FIGS. FIG. 8 shows an example of an electronic document that has not been updated after creation. Note that this electronic document includes “Iroha nihongo niruru” as description contents.
[0059]
On the other hand, when the first update process is performed, first, the part of “Chiryuru” is deleted, and then, the remaining “Iroha niho hito” is replaced with “Iroha niho hello niru”. The update record 26 is added to the electronic document 20. The update recording portion 26 includes the update difference information 27, and “Chiruniru” is deleted in the description portion sandwiched between <Update Seg = "1" ...> and </ Update>. Next, in the description part sandwiched between <Update Seg = "2" ...> and </ Update>, "Iroha niho hito" is once deleted, and instead, "Iroha niho hello" is inserted.
[0060]
A history guarantee signature 28 for the update difference information 27 is inserted. Also, as a result of this update, the text 21 is finally updated to “Iroha nihongo jiru nuru”.
[0061]
After the first update shown in FIG. 9, if “Iroha niho ni kurinuriru” is deleted and “Iroha niho ni kurinuriru is inserted” is inserted as a second update, the description of the electronic document is shown in FIG. As shown in FIG. In FIG. 10, the electronic document 20 includes an update record 27 related to the first update and a second update record 27. In addition, due to the second update, the main text 21 is finally changed to “I want to make it all the way through Iroha.”
[0062]
In the examples shown in FIGS. 8 to 10, for convenience of explanation, the text of the original electronic document (before the update) is simply “Irohani Hijiri Nuri”. However, since the description of the text is much more in the actual electronic document than in this example, the ratio of the update history information is relatively small relative to the text. Therefore, by storing only the difference information in the electronic document, it is possible to reliably restore the update history over the past multiple generations without increasing the data capacity.
[0063]
【The invention's effect】
As described above, according to the present invention, an electronic document of a target generation can be restored by going back to the generation, and the electronic signature of the generation can be verified using the restored electronic document. Therefore, even when a single electronic document has been updated multiple times, it is possible to restore an electronic document in any generation and verify the electronic signature in that generation, and thus a reliable electronic document Guarantees can be realized.
[0064]
In addition, since the update history information created in the document update process to restore the past electronic document is difference data before and after the update in each generation, the electronic document is stored as it is for each generation. In general, the data capacity can be considerably reduced. Therefore, it is possible to store a large number of generations of electronic documents in a retrievable manner with a small amount of stored data.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of document update processing and document restoration processing by an electronic document processing apparatus of the present invention.
FIG. 2 shows an example of the data structure of an electronic document.
FIG. 3 is a flowchart of document update processing.
FIG. 4 is a diagram illustrating document restoration processing.
FIG. 5 is a flowchart of document restoration processing.
FIG. 6 shows a description example of update history information.
FIG. 7 is a diagram illustrating a method for describing update records.
FIG. 8 is a description example of an unupdated electronic document.
FIG. 9 is a description example of an electronic document after the first update.
FIG. 10 is a description example of an electronic document after the second update.
[Explanation of symbols]
7, 11 Electronic document processing program
8,12 Browser function
9, 13 Document creation function
10 Update history creation function
15 Electronic document restoration function
20 Electronic documents
21 Text
22 Electronic signature
25 Update history information
26 Update record
27 Update difference information
28 History Guarantee Signature

Claims (14)

Document processing means for creating or updating an electronic document;
Update history creation means for extracting a history of updates made to the electronic document through the document processing means and storing the history in association with the electronic document as update history information,
The update history information includes difference information between an electronic document before update and an electronic document after update, and an electronic signature created using the difference information as target data . The update history information is generated for each update operation, and the update history information includes generation information indicating how many times the update operation is performed on the electronic document. electronic document processing apparatus according to 1. It said update history creation means, the update history information, the electronic document processing apparatus according to claim 1 or 2, characterized in that included in the electronic document as the body data and separate information of the electronic document. The document processing means stores the updated electronic document as body data, and stores the electronic signature created using the updated electronic document as target data in the electronic document. Item 4. The electronic document processing apparatus according to any one of Items 1 to 3 . Display means for reading and displaying an electronic document;
Based on the electronic document and update history information related to the electronic document, a document restoring means for restoring an electronic document of a past generation created by an update operation,
The update history information includes difference information between the electronic document before update and the electronic document after update, and an electronic signature created using the difference information as target data,
The electronic document processing apparatus , wherein the document restoration means restores the electronic document only when the electronic signature is successfully verified . The electronic document includes an electronic signature created using the updated electronic document as target data,
6. The electronic document processing apparatus according to claim 5 , wherein the document restoration unit further includes a verification unit that verifies an electronic signature corresponding to the electronic document of the generation using the restored electronic document. A specifying means for inputting a specification of the generation of the electronic document to be restored;
The electronic document processing apparatus according to claim 5 , wherein the document restoration unit restores the electronic document of the generation designated by the designation unit. Document processing means for creating or updating an electronic document;
The computer functions as an electronic document processing apparatus comprising: an update history creation unit that extracts a history of updates performed on the electronic document through the document processing unit and stores the update history information in association with the electronic document. Let
The computer program , wherein the update history information includes difference information between an electronic document before update and an electronic document after update, and an electronic signature created using the difference information as target data . The update history information is generated for each update operation, and the update history information includes generation information indicating how many times the update operation is performed on the electronic document. The computer program according to 8 . The computer program according to claim 8 or 9 , wherein the update history creating means includes the update history information in the electronic document as information separate from text data of the electronic document. The document processing means stores the updated electronic document as body data, and stores the electronic signature created using the updated electronic document as target data in the electronic document. Item 11. The computer program according to any one of Items 8 to 10 . Display means for reading and displaying an electronic document;
A computer is caused to function as an electronic document processing apparatus comprising: the electronic document; and document restoration means for restoring an electronic document of a past generation created by an update operation based on the update history information related to the electronic document. ,
The update history information includes difference information between the electronic document before update and the electronic document after update, and an electronic signature created using the difference information as target data,
The computer program for restoring the electronic document only when the electronic signature is successfully verified . The electronic document includes an electronic signature created using the updated electronic document as target data,
13. The computer program according to claim 12, wherein the document restoration unit further includes a verification unit that verifies an electronic signature corresponding to the generation of the electronic document by using the restored electronic document. A specifying means for inputting a specification of the generation of the electronic document to be restored;
The computer program according to claim 12 or 13 , wherein the document restoration means restores the electronic document of the generation designated by the designation means.

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