JPH10283262A - File system and program recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a file system which manages a main file in such form that alteration can be detected. SOLUTION: If a file write request from an application program execution system 11 which executes an application program is new one, a file system 12 stores a main file 21 including data, whose write is requested, in a storage device 13 and generates an authentication file 22 including a signature (check sum), the generation date of the main file 21, generator information, etc., generated from contents of the main file 21 and stores the generated authentication file 22 in the storage device 13 corresponding to the main file 21. When the existing main file 21 is updated, the signature, the update date, updater information, etc., of the main file 21 after update are added to the authentication file 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a file system and a program recording medium, and more particularly, to a file system and a computer system capable of storing a file in a rewritable storage device in a form in which the presence or absence of tampering is known. The present invention relates to a program recording medium for functioning as a system having functions.

[0002]

2. Description of the Related Art In recent years, various types of information have been stored and reused in storage devices provided in computer systems. The form of reuse includes updating the contents of an existing file, modifying the contents of an existing file and storing it as a new file, and transferring the contents of the file to another computer system via a communication line. There is something to transfer.

[0003]

As described above, if a computer system is used, existing information can be processed or reused as it is, so that various operations can be completed efficiently. At this time, if the information created as a result of the work is stored in a storage device (on a storage medium) that can be physically written only once, the information in the storage device is stored by the creator. Can be said to be as created. However, when the information is stored in a rewritable storage device, certifying that the information (file) is as created by the creator is easy because the information is easily processed. On the contrary, it is difficult.

[0004] In addition, when updating, copying, moving, and the like of contents are repeated, there is another problem that it is difficult to know how the information (file) was created.

An object of the present invention is to provide a file system capable of managing a file in a rewritable storage device in a form in which the presence or absence of tampering can be recognized. Another object of the present invention is to provide a file system capable of managing files in a form in which a past processing history can be understood.

Another object of the present invention is to provide a program recording medium for causing a computer system to function as a system in which files are stored in a form in which the presence or absence of tampering can be recognized.

[0007]

According to a first aspect of the present invention, there is provided a main file storage means for storing a main file, which is a file instructed to be stored, in a storage means. An authentication information creating unit that creates authentication information including a signature, which is information that can be used to verify data in the main file stored by the main file storage unit, and authentication information created by the authentication information creating unit. A file system is configured by using a sub-file storage unit that stores the sub-file in the storage unit in a form in which the correspondence with the main file can be understood.

According to this file system, the main file can be managed in a form in which the presence or absence of tampering can be recognized. When the file system according to the first aspect is realized, if a sub-file associated with the main file exists in the storage unit as the sub-file storage unit, the sub-file is stored in the authentication information creation unit. It is desirable to employ means for adding the authentication information created by the above.

[0009] After adopting such sub-file storage means, authentication information creation means for creating authentication information including information indicating the storage date and time of the main file in the main file storage means, and a user who instructs storage of the main file. If an authentication information creating unit or the like that creates authentication information including information about the main file is adopted, a file system that can manage the contents of the processing performed on the main file in the past can be obtained.

[0010] In the file system according to the first aspect,
An authentication information creating means for creating authentication information including access form defining information for defining an access form which can be performed on the main file is employed. When an access request to the main file stored in the storage means is made, the access request is made. However, a response unit that responds to the access request can be added only when the access mode specified in the access mode definition information in the sub file corresponding to the main file is conformed.

[0011] Further, as the authentication information creating means, means for creating authentication information including expiration date information indicating the expiration date of the access mode defining information is used, and the current date and time and the expiration date information in the sub-file stored in the storage means are used. Based on the above, it is also possible to add an updating means for specifying the sub-file whose expiration date has expired and updating the contents of the access mode defining information of the specified sub-file.

Further, the file system according to the first aspect includes:
When the copying of the main file is instructed, processing including transfer of the data in the main file and the data in the sub-file corresponding to the main file to the copy destination is executed, and A main file copying unit for adding information indicating that the corresponding main file is a copied file, and generating a main file and a sub file on the storage unit based on data transferred as a result of the copy instruction. And in the generated sub-file,
It is also possible to add a copied main file generating means for adding information indicating that the corresponding main file is a copy of another main file.

Further, the file system according to the first aspect includes:
When the transfer of the main file is instructed, a process including transfer of the data in the main file and the data in the sub-file corresponding to the main file to the transfer destination is executed. A main file moving unit for erasing the sub file from the storage unit, a main file and a sub file are generated in the storage unit based on the data transferred as a result of the move instruction, and a main file corresponding to the generated sub file is generated. A moved main file generating means for adding information indicating that the file is the original may be added.

Then, the file system may be configured so that the sub-file is a file encrypted using a certain key. At this time, the file system is configured so that a key including the identification information given to the storage unit, a key including the identification information given to the file system, and a key including the key given by the user are used as the keys. Can be configured. When the file system is configured in this manner, it becomes more difficult to falsify the sub-file, so that a file system that can more accurately determine whether the main file has been falsified can be obtained.

[0015] The file system may be configured so that one device is physically used as the storage means, but the first storage means used for storing the main file includes:
The file system may be configured so as to use a storage unit that is used for storing the sub-file and includes a second storage unit that cannot be updated by the user.

According to a second aspect of the present invention, a main file storage means for storing a main file, which is a file instructed to be stored, in a storage means, and a main file in the main file stored by the main file storage means. The correspondence between the main file and the authentication information creating means for creating authentication information including a signature which is information that can be used for data verification, and the sub-file holding the authentication information created by the authentication information creating means can be understood. In addition, a file system is configured using the sub-file storage unit stored in the storage unit without deleting the sub-file associated with the main file already existing in the storage unit.

That is, in the file system according to the second aspect, not one authentication file but one authentication file corresponding to the number of processes performed in the past on the main file, not on one main file. Be managed.

When the file system of the second aspect is realized, as the sub-file storing means, means for storing, in the storing means, a sub-file in which the authentication information holds data encrypted with a key given by the user. Can be adopted.

Further, the file systems of the first and second aspects can be constituted by realizing all or a part of the sub-file storage means by a medium control mechanism in the storage device.

Further, the computer system is provided with storage means for storing a file, main file storage means for storing a main file, which is a file designated to be stored by an application program, in the storage means, An authentication information creating unit that creates authentication information including a signature that is information that can be used for verifying data in the main file stored by the storage unit; and a sub-file that includes authentication information created by the authentication information creating unit. Using a program recording medium on which a program for functioning as a sub-file storage unit that is stored in the storage unit in a form in which the correspondence relationship with the main file is understood,
A file system as described above can also be realized.

[0021]

Embodiments of the present invention will be specifically described below with reference to the drawings. As schematically shown in FIG. 1, the file system 12 according to the embodiment includes a storage device 1
3 is realized as one function of the computer system 10 having the C.I. That is, the file system 12 is realized by installing an operating system (OS) to which a program for executing each process described later is added in the computer system 10.

The OS is a computer system 10
Is also operated as an application program execution system 11 that executes processing according to the application program. When executing a process that requires access to a file in the storage device 13, the application program execution system 11 requests the file system 12 to execute the process. In the present embodiment, a magneto-optical disk device is used as the storage device 13.

The file system 12 performs processing (control) on the storage device 13 in accordance with the contents of a request from the application program execution system 11. The main processes performed by the file system 12 include a file creation process, a file update process,
There are file copy processing, file movement processing, and file verification processing. Hereinafter, details of each process will be sequentially described.

First, details of the file creation processing will be described. The file creation process is a process in which data newly created by the application program execution system 11 is filed and stored in the storage device 13. At the time of the file creation processing, the file system 12 stores the main file 21 which is a file holding the data in the storage device 13, as in a general file system. Further, the file system 12 stores the main file 2 based on the contents of the stored main file 21 and the like.
Various types of information to be stored in association with 1 are determined.
Then, an authentication file 22 holding authentication information including the determined information is stored in the storage device 13. At this time, the file system 12 registers information for associating the stored authentication file 22 with the main file 21 in the file management table 23. In the present embodiment, as the file management table 23, as schematically shown in FIG. 2, the position where the main file identified by the "file name" is stored corresponding to the "file name" of the main file. And a "pointer to the authentication file" indicating the location where the authentication file corresponding to the main file is stored.

Hereinafter, the operation of the file system 12 during the file creation processing will be described more specifically with reference to FIGS. FIG. 3 is a diagram showing the operation flow of the file system 12 during the file creation process together with the operation flow of the application program execution system 11, and FIG. FIG. 4 is an explanatory diagram of a main file and an authentication file stored in the storage device.

When the file creation processing is executed, FIG.
As shown in (a), the application program execution system 11 opens a new file (step S101), creates a file (step S102),
A series of processes such as a file write instruction (step S103) and a file close (step S104) are executed. In response, the file system 12
As shown in FIG. 3B, first, the contents of the file instructed to be written are stored as the main file 21 in the storage device 1.
3 is performed (step S11).
1). Next, the file system 12 creates a signature (checksum) based on the contents of the main file 21 (step S112). And file system 1
2 stores (creates), on the medium of the storage device 13, the authentication file 22 holding the authentication information including the created signature and several other types of information (step S113). In this step, the file system 12
As described above, the main file 21 and the authentication file 2
2 is stored in the file management table 23.
It also performs the process of registering within. The file system 12
As shown in FIG. 4, as information other than the signature (checksum), the identification information of the user who started the application program execution system 11 (“user A”) and the storage date information of the main file 21 (“Dec. .1
6 ”), an authentication file 22 including information (“ newly created ”) indicating that the main file 21 is a file created on the date represented by the storage date information is created.

Next, the operation of the file system 12 during the file update processing will be described with reference to FIGS.
5 is a diagram showing the operation flow of the file system 12 at the time of file update processing together with the operation flow of the application program execution system 11, and FIG. 1
FIG. 3 is an explanatory diagram of a main file and an authentication file stored on a third medium.

When the file update process is executed, the process shown in FIG.
As shown in (a), the application program execution system 11 opens an existing file (step S201) and reads the contents of the opened existing file (step S202). In response, the file system 12, as shown in FIG.
A process of reading the contents of the existing file (main file) instructed to be read from the medium and supplying it to the application program execution system 11 is performed (step S2).
11).

Thereafter, the application program execution system 11 updates the content of the read existing file (step S203) and writes the existing file whose content has been updated (step S20).
4), a series of processes such as closing a file (step S205).

In response, the file system 12
Performs a process of storing the contents of the updated existing file on the medium as the main file 21 (step S21).
2). Next, the file system 12 creates a signature (checksum) based on the contents of the main file 21 (step S213). And file system 1
2 adds the authentication information including the created signature and some other types of information to the authentication file 22 already stored on the medium (step S214). For example, when the contents of the main file shown in FIG. 4 are updated, as shown in FIG. 6, the file system 12 adds the created signature and the contents of the main file 21 to the contents of the original authentication file. The identification information (“user B”) of the user who has updated (the content program has been updated by activating the application program execution system 11) and the storage date information of the file (“1996.12.
17 "), and information (" content update ") indicating that the main file 21 is a file updated on the date indicated by the storage date information is added.

Next, the file copying process will be described. The file copying process includes a process of copying a file to a storage device directly managed by the file system 12 and a process of copying a file to a storage device managed by another file system via a communication line. There is. Since the basic operation procedure in both processes is the same, here,
Only the operation of the file system 12 during the latter processing will be described. In the following description, for convenience, the file system 12 on the side that starts the file copying process through communication is referred to as a transmission-side file system,
The file copy processing by communication executed in the transmission-side file system is referred to as file copy transmission processing. Further, the file system 12 that receives the data transmitted by the file copy transmission processing is referred to as a receiving file system, and the receiving file system stores, in a medium of a storage device managed by itself, a main file corresponding to the received data. Processing for storing a file or the like is referred to as file copy reception processing.

FIGS. 7 and 8 show the operation procedure of the transmitting file system and the receiving file system at the time of file copy transmission processing and file copy reception processing, respectively. The flowcharts shown in the figures are started when the corresponding application program execution system instructs copy transmission and copy reception of a file.

As shown in FIG. 7, when a copy and transmission of a file is instructed, the transmission-side file system recognizes a main file to be transmitted, and also recognizes a transmission instructor (user) and a transmission destination ( Step S301). Next, the transmission-side file system reads the recognized main file and the authentication file corresponding to the main file from the storage device (step S302), and reads the main / authentication file, which is a file obtained by combining the main file and the authentication file. Is transmitted to the transmission destination (step S303).

On the other hand, the receiving file system which has received the main / authentication file transmitted in this step via the application program execution system, sets the main / authentication file as the main file as shown in FIG. At the same time as the authentication file is separated, the sender and the receiver (user) are recognized (step S401). Thereafter, the receiving file system stores the separated main file and the authentication file on the medium of the storage device (step S40).
2). Next, the receiving file system authenticates the authentication information (details will be described later) including information indicating that the stored main file is a copy of the file held by the transmission source and a signature of the main file. The file is added to the file (step S403). Then, the write completion notification is sent to the main /
The authentication file is transmitted to the transmission source (step S404), and the illustrated processing ends.

As a result of such an operation of the receiving file system, the transmitting file system receives the write completion notification after transmitting the main / authentication file to the destination. Then, as shown in FIG. 7, upon receiving the write completion notification, the transmission-side file system adds the authentication information including the information on the executed file copy transmission to the authentication file on the medium (step S304). Then, the process ends.

For example, when the main file shown in FIG. 6 is copied and transmitted, as shown in FIG. 9, the transmission side file system generates a copy of the main file corresponding to the contents of the original authentication file as shown in FIG. Information (“file copy”, “copy destination = □□”), identification information of the user who made the copy (“user C”), and the date when the copy was made (“1996.12.18” ) And authentication information including the same signature as the signature included in the immediately preceding authentication information.

On the other hand, in the receiving file system, FIG.
0, information indicating that the transmitted main file has the contents of the transmitted authentication file and further indicates that the corresponding main file is the file transmitted and transmitted (“file copy”, “copy source = × × ”), the received user identification information (“ user X ”), and the date of copying (“ 1996.1
2.18 "), an authentication file having authentication information including a signature generated from data of the main file is created and stored.

As described above, when a file is copied and transmitted between two computer systems equipped with the file system, information on the transmission destination is stored in the computer system on the side that transmitted the main file. The generated authentication file is generated. Then, in the computer system that has received the main file, an authentication file holding information on the computer system (source) where the main file originally existed is generated.

Next, the file transfer processing will be described. The file movement process includes a process of moving a file through a communication line and a process of moving a file in a storage device directly managed by a file system. Since the basic operation procedure in both processes is the same, only the former process will be described below. In the following description, as in the description of the file copy process, the file system 12 that starts the file transfer process by communication is referred to as a transmission file system, and the communication is performed by the transmission file system. The file transfer process is referred to as a file transfer process. Further, the file system 12 that receives the data transmitted by the file transfer process is referred to as a receiving file system, and the receiving file system stores a main file corresponding to the received data in a storage medium managed by itself. The process of storing such as is described as a file transfer reception process.

FIG. 11 shows a flow of the file transfer process executed by the transmitting file system. As shown in the figure, at the time of the file move transmission process, the transmission-side file system first executes the same processing (steps S501 to S503) as the file copy transmission process, so that the computer system (reception) designated as the transmission destination is performed. A main / authentication file obtained by combining the main file designated to be moved and the authentication file corresponding to the main file. Next, the transmission-side file system waits for input of the write completion notification from the reception-side file system, and upon receiving the write completion notification, deletes the transmitted main file and authentication file from the medium ( Step S504) is performed. Then, the illustrated process ends.

On the other hand, in response to the file transfer process,
As shown in FIG. 12, the file transfer receiving process executed by the receiving file system is almost the same as that shown in FIG.
This is the same process as the file copy reception process. However, in the file moving process, in step S603, authentication information including information indicating that the stored file is the moved file is added to the authentication file.

For example, if the file system on the transmission side is as shown in FIG.
When the main file shown in (1) is moved and transmitted, the receiving file system indicates that the main file corresponding to the content of the received original authentication file has been moved, as shown in FIG. Information (“file move”, “move source = xxx”), identification information of the user who received the main file (“user X”), and date of the move (“19
96.12.18 ") and an authentication file to which authentication information including a signature created from the main file is added is stored in the storage device.

Finally, the file verification processing will be described.
As described above, in a computer system including the file system according to the embodiment, or in a computer network system in which the computer system is connected via a communication line, updating, copying,
If the transfer is performed, the contents of the processing performed on the main file, the processing date, information indicating the executor of the processing, and the like after the processing are performed in the authentication file without the user's (application program) 's awareness Authentication information including a signature corresponding to the content of the main file of the above is added.

The file verification process determines whether or not the main file has been falsified based on information in the authentication file, and outputs (displays) a processing history of the main file. When the user wants to verify the presence or absence of tampering or wants to know the processing history, the user performs a series of operations on the computer system including input of the main file name to be verified. To perform file verification processing.

FIG. 14 shows an operation procedure of the file system 12 during the file verification process. As shown in the figure, at the time of the file verification process, the file system 12 first reads out the contents of the main file designated as the verification target and the contents of the authentication file corresponding to the main file from the storage device (step S701). Next, the file system 12 creates a signature from the read contents of the main file, and compares the created signature with the latest signature in the authentication file to determine whether the main file has been tampered with (step S702). That is, if the contents of both signatures match, it is determined that the signature has not been tampered with. If the signatures do not match, it is determined that some tampering has been performed on the main file to be verified. judge. Then, the result of determining whether or not there is tampering and each authentication information (excluding the signature) in the authentication file are output (step S70).
3) Then, the illustrated processing ends.

As described above in detail, according to the computer system having the file system of the embodiment, it is possible to determine whether or not the main file has been tampered with, and to execute the processing performed on the main file in the past. Can be managed in a form that can be understood.

<Modification> In the file system of the embodiment, in order to associate the main file with the authentication file,
Although the system uses the file management table, the means that can be adopted to associate the two files is not limited to this. For example, the information (abcdef.xyz → abcdef.xyz *) with special characters that cannot be used as a file name after the main file name is used as the authentication file name. The file system can be configured so that the result of performing a predetermined process is used as an authentication file name.

The file system of the embodiment is a system for moving and copying a file via a communication line without performing encryption. However, in order to enhance security on a communication network, the main file and the file are moved. The encryption process and signature creation / attachment process are performed on the main / authentication file combined with the authentication file, and as a result (encryption main /
The file system may be configured so that the authentication file is transmitted to the transmission destination via the communication line. Naturally, in this case, the signature verification processing and the decryption processing are performed when the encrypted main / authentication file is received.

A storage device for storing the authentication file and a storage device for storing the main file may be separately provided. In this case, a write-once storage device may be used as a storage device for storing the authentication file.

The authentication file stores access mode definition information for defining an access mode (for example, read / write enabled, read only enabled, read / write disabled, etc.) that can be performed on the main file. When a request to access a file is made, the access request is responded to only when the access request conforms to the access mode specified in the access mode specification information in the authentication file corresponding to the main file. The file system may be configured to perform

Further, in the authentication file, expiration date information indicating the expiration date of the access mode definition information is included, and based on the current date and time and the expiration date information in the authentication file, the authentication file whose expiration date has been reached is specified. Then, the file system can be configured so as to change the content of the access mode defining information of the specified authentication file (or to delete the main file).

Further, it goes without saying that some or all of the functions of the file system of the embodiment may be provided on the storage device side.

[0053]

As described above, according to the file system of the present invention, the main file can be managed in a form in which the presence or absence of falsification can be recognized. Further, according to the program recording medium of the present invention, a computer system can function as a system including such a file system.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a configuration of a file system according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a file management table used by the file system according to the embodiment.

FIG. 3 is a flowchart of an operation of a file system and an application program execution system during a file creation process.

FIG. 4 is an explanatory diagram of an operation during a file creation process of the file system according to the embodiment.

FIG. 5 is a flowchart of an operation of a file system and an application program execution system during a file update process.

FIG. 6 is an explanatory diagram of an operation at the time of a file update process of the file system according to the embodiment.

FIG. 7 is a flowchart of a file copy transmission process executed by the file system of the embodiment.

FIG. 8 is a flowchart of a file copy reception process executed by the file system of the embodiment.

FIG. 9 is an explanatory diagram of an authentication file generated at the time of file copy transmission processing.

FIG. 10 is an explanatory diagram of an authentication file generated at the time of file copy reception processing.

FIG. 11 is a flowchart of a file transfer process executed by the file system according to the embodiment.

FIG. 12 is a flowchart of a file transfer reception process executed by the file system of the embodiment.

FIG. 13 is an explanatory diagram of an authentication file generated at the time of file transfer reception.

FIG. 14 is a flowchart of a file verification process executed by the file system of the embodiment.

[Explanation of symbols]

 Reference Signs List 10 computer system 11 application program execution system 12 file system 13 storage device 21 main file 22 authentication file 23 file management table

Claims (17)

[Claims] 1. A main file storage means for storing a main file, which is a file instructed to be stored, in a storage means, and information usable for verifying data in the main file stored by the main file storage means. An authentication information creating means for creating authentication information including a signature, and a sub-file containing authentication information created by the authentication information creating means are stored in the storage means in a form in which a correspondence relationship with the main file can be understood. A file system comprising: a sub-file storage unit. 2. The storage device according to claim 1, wherein the sub-file storage unit stores, in the storage unit, the authentication information generated by the authentication information generation unit in the sub-file, if the sub file associated with the main file exists. The file system according to claim 1, wherein the file system is added. 3. The file system according to claim 1, wherein the authentication information creating unit creates authentication information including information indicating a date and time when the main file is stored in the main file storage unit. . 4. The file system according to claim 1, wherein the authentication information creating unit creates authentication information including information on a user who has instructed to store the main file. . 5. The authentication information creating unit creates authentication information including access mode defining information that defines an access mode that can be performed on the main file, and an access request to the main file stored in the storage unit is issued. When there is a request, only when the access request conforms to the access mode defined by the access mode definition information in the sub-file corresponding to the main file, responding means for responding to the access request, The file system according to any one of claims 1 to 4, further comprising: 6. The authentication information creation unit creates authentication information including expiration date information indicating an expiration date of the access mode defining information, and stores a current date and time and an expiration date in the sub-file stored in the storage unit. 6. The file system according to claim 5, further comprising updating means for specifying a sub-file whose expiration date has expired based on the information, and updating the contents of the access mode definition information of the specified sub-file. 7. When copying of a main file is instructed, processing including transfer of data in the main file and data in a sub-file corresponding to the main file to a copy destination is executed, and the storage is performed. Main file copying means for adding information indicating that the corresponding main file is a copied file to the sub file on the means; and storing the data on the storage means based on the data transferred as a result of the copy instruction. A copy main file generation unit that generates a main file and a sub file, and adds information indicating that the corresponding main file is a copy of another main file to the generated sub file. The file system according to claim 1. 8. When a move of a main file is instructed, a process including transfer of data in the main file and data in a sub-file corresponding to the main file to a transfer destination is executed. A main file moving unit for erasing the main file and the sub file from the storage unit after completion; generating a main file and a sub file on the storage unit based on data transferred as a result of the moving instruction; The moving main file generating means for adding information indicating that the corresponding main file is the original to the sub-file thus obtained is further provided.
File system according to any of the above. 9. The file system according to claim 1, wherein the sub-file is a file encrypted using a certain key. 10. The file system according to claim 9, wherein said key includes identification information given to said storage means. 11. The file system according to claim 9, wherein the key includes identification information given to the file system. 12. The file system according to claim 9, wherein the key includes a key given by a user. 13. The storage means comprises: a first storage means used to store a main file; and a second storage means used to store a sub-file and whose contents cannot be updated by a user. The file system according to claim 1. 14. A main file storage means for storing a main file, which is a file instructed to be stored, in a storage means, and information usable for verifying data in the main file stored by the main file storage means. Authentication information creating means for creating authentication information including a signature, and a sub-file holding the authentication information created by the authentication information creating means, wherein the correspondence between the main file and the main file is known, and And a sub-file storage unit that stores the sub-file associated with the main file already existing in the storage unit in the storage unit without deleting the sub-file. 15. The sub-file storage unit according to claim 14, wherein the sub-file storage unit stores a sub-file in which the authentication information holds data encrypted with a key given by a user in the storage unit. File system. 16. The file system according to claim 1, wherein all or a part of said sub-file storage means is realized by a medium control mechanism in a storage device. 17. A computer system comprising: storage means for storing a file; main file storage means for storing a main file, which is a file designated to be stored by an application program, in the storage means; An authentication information creation unit that creates authentication information including a signature, which is information that can be used to verify data in the main file stored by the file storage unit; and a sub-file that includes authentication information created by the authentication information creation unit. And a program recording medium on which a program for functioning as a sub-file storage means stored in the storage means in a form in which a correspondence relation with the main file is understood.