JP2003131567A - Alteration preventing method, program, alteration prevention system, recipient-side processor, reporter-side processor, data recording system, game service system with game log alteration preventing means, provider-side processor, and user-side processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which enables a recipient side to detect data, reported from a reporter, being altered in such a case to prevent the reporter from altering the data. SOLUTION: A secret key A that only the recipient knows is embedded in a program including a process of recording data on a recording medium and a program X including a digital signature process of recording the data on the recording medium together with a digital signature A based upon the secret key A in the former program is generated on the recipient side and this program is installed on a reporter-side processor and used. The reporter is made to record the data with the digital signature on the recording medium based on the program X and the recipient receives the data with the digital signature and performs signature verification with an open key A paired with the secret key A to verify that the data are not altered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for preventing falsification of data.

[0002]

2. Description of the Related Art Conventionally, digital signatures have been known as a technique for guaranteeing the validity of documents and data. By using such a digital signature, for example, a log recording sales is digitally signed with a secret key held by a sales manager, and the sales log with the digital signature is transmitted to the management headquarters, and the management headquarters By verifying the digital signature with the sales manager's public key, the manager confirms that the sales log from the sales manager was created by the sales manager and has not been tampered with on the way. be able to. However, since the sales management person himself / herself can change the sales log arbitrarily, it is impossible to prevent fraud such as deleting a part of the log to cheat the sales.

By the way, with the spread of the Internet in recent years, a service has been developed in which, when a game is played on a network and a free gift is obtained, the free gift is actually sent. When such a service is developed on the network by the game developer itself, it is possible to prevent fraud by applying a security check or the like to the game management server to prevent intrusion from the outside.
However, if such a service is to be developed, for example, in a restaurant or hotel, that is, if game terminals are installed in these stores and the game price is settled outside the control of the game developer, Such inconvenience occurs.

For example, assuming that payment of game price is managed in conjunction with a POS system managed by a restaurant or a hotel side (hereinafter referred to as a user side) for convenience, the user side has the POS system. Sales report data will be created based on the system and reported to the game system provider.

[0005]

Here, as described above, even if the sales report data is encrypted and reported to the game system provider, if the user is tampered with, the game content provider will There is a possibility that it may not be possible to confirm whether fraud has been made, and thus it may not be possible to obtain valid sales.

The present invention has been made in view of such a problem, and when the data reported by the reporter is falsified, the recipient can detect the falsification and prevent the falsification of the data by the reporter. To provide technology for

[0007]

A tampering prevention method according to the present invention comprises a recipient-side processing device on the data recipient side and a reporter on the data reporter side for creating data to be passed to the recipient-side processing device. A system configured with a side processing device, which is a method for preventing data falsification by a data reporter,
The receiver side processing device embeds the secret key A known only to the receiver in a program including a process of recording data on a recording medium, and when data is recorded according to the recording process, the secret key in the program is stored in the data. A program X including a digital signature process for adding a digital signature A by the key A and recording it on a recording medium is created, and the program X is installed in a processing device on the reporter side to be used. When the digitally signed data created on the basis of it is received, the public key A which is a pair with the private key A
The signature verification is performed in order to verify the validity of the data, and the reporter side processing device installs and executes the program X,
When data is recorded on a recording medium according to the recording process of the program X, the digital signature A by the secret key A in the program X is added to the data and recorded on the recording medium, and the data with digital signature is given to the recipient. Is.

[0008]

FIG. 2 is a system configuration diagram to which a falsification prevention method according to an embodiment of the present invention is applied. Figure 2
In the figure, 1 is a processing device on the data receiver side, and 11 is a processing device on the data reporter side. The recipient side processing device 1 is
An apparatus that creates a program X with a data tampering prevention function for causing a reporter to report valid data, and installs the program X in the reporter-side processing device 11 to generate and record data based on the program X. This prevents the reporter from tampering with the data.

The recipient-side processing device 1 embeds the secret key A known only to the recipient in a program including a recording process for recording data on a recording medium, and records the data according to the recording process. Program creating means 2 for creating a program X including a digital signature process for adding a digital signature A by the secret key A in the program to a data recording medium, and a program X created by the program creating means 2. In addition, the encryption means 3 for creating the digital signature-attached program X to which the digital signature B is added by the secret key B known only to the recipient, and the digital-signature-attached data received from the reporter-side processing device 11 as the secret key A. Recipient side signature verification means 4 for verifying the validity of the data by verifying the signature with the public key A as a pair.
It has and.

The reporter-side processing device 11 installs the digitally signed program X created on the recipient side,
The digital signature added to the program X with digital signature is validated by the reporter-side signature verification means 12 for verifying the signature with the public key B which is a pair with the secret key B, and the reporter-side signature verification means 12. And the executing means 13 for executing the program X.

FIG. 1 is an explanatory diagram of an alteration prevention method according to an embodiment of the present invention. In the recipient-side processing device 1, the program creation means 2 causes the program including the recording processing for recording the data in the recording medium to the secret key A known only to the recipient.
Embed. Then, when data is recorded according to the recording process, a program X including a digital signature process for adding the digital signature A by the secret key A in the program to the data and recording it on a recording medium is created. . Then, the encryption means 3 adds the digital signature B by the secret key B known only to the recipient, that is, the digital signature B generated by using the program X and the secret key B, to the program X created by the program creating means 2. Then, the digitally signed program X is created.

The digital signature-attached program X is installed in the reporter-side processing unit 11, and when the digital signature-attached program X is executed, first, the digital key-attached program X is converted into the digital signature-attached program X using the public key B of the recipient. The validity of the program X is verified by verifying the signature of the added digital signature B. If this verification is NG, that is, if any alteration is made to the program X, a program alteration error occurs and execution is hindered. In this way, since the tampering of the program X itself can be prevented by adding the digital signature B to the program X and encrypting the program X, the program X is tampered with so that illegal data is prevented from being recorded in the recording medium. The act can be prevented.

If the verification is OK, the program X is started and the processing by the program X is executed. When the recording process is performed based on the program X, the digital signature process causes the digital signature A by the secret key A embedded in the program X, that is, the digital signature A generated by using the data and the secret key A to be recorded. It is added and recorded on the recording medium. In this way, the data recorded on the recording medium has the digital signature A generated by the secret key A embedded in the program X, that is, the secret key A known only to the recipient.

Then, the recipient receives the digitally signed data from the reporter, verifies the digital signature A of the digitally signed data with the public key A which is a pair with the private key A, and verifies the data. Verify sex. If this verification is OK, the validity of the data can be confirmed. On the other hand, if the verification is NG, a data tampering error occurs and it can be detected that the data has been tampered with.

As described above, when data is recorded on the recording medium by the reporter, the data is encrypted with the secret key A known only to the recipient, that is, the digital signature A is generated and added and recorded. Only the recipient who holds the public key A can verify the legitimacy of the above. If the data is falsified, the public key A cannot be decrypted and the recipient can detect fraudulent behavior. It is possible to prevent tampering with. In addition to this, the reporter who installs and uses the program with the digital signature in order to encrypt (generate and add the digital signature B by the private key B known only to the recipient) to the program X itself which performs this recording process. When the program X is tampered with on the side, the public key B of the reporter cannot be used for decryption. Therefore, program X
It is possible to prevent tampering of itself, and thus it is possible to reliably prevent tampering of data.

FIG. 3 is a block diagram of a game service system showing an application example of the present invention. Reference numeral 21 is a processing system on the game content provider side, 31 is a processing system on the game content user side, specifically, for example, a restaurant or hotel side. The provider side processing system 21 and the user side processing system 31 form a network NET. Connected through. Here, the game content provider is to install an intranet type game system 41 in a service floor provided by the game content user side (for example, in a store in the case of a family restaurant), and sell the game terminal 44 with the game. It is a company that acquires it based on sales report data from the content users.

The provider side processing system 21 includes a game management server 22 corresponding to the above-mentioned recipient side processing device 1.
And a game log DB that stores the encrypted game log that is regularly transferred from the game content user side.
And 23.

A game system 41 provided by the game content provider is installed in the user side processing system 31 on the side of the game content user. The game system 41 is connected via a network to a POS system 32 that has been conventionally provided in the user-side processing system 31, and sales of the game system 41 are PO.
It is designed to be managed in conjunction with the S system 32. Then, the game content user creates sales report data in the game system 41 based on the POS system 32 and reports it to the game content provider.

The game system 41 comprises a plurality of game terminals 44, a game log DB 43 in which game logs of each game terminal 44 are stored, and a game content server 42 which manages the game terminals 44 and the game log DB 43. There is. The game content server 42
This is equivalent to the reporter-side processing device 11 in FIG. 2, and a game log recording program, which is created by the game service provider and corresponds to the above-mentioned program X, is installed inside with a digital signature with the secret key B. .

Further, in the game content server 42,
According to this game log recording program, at a predetermined processing stage (S4, S7, S11, S15 in FIG. 4, which will be described later), data relating to game sales is encrypted as a game log and recorded in the game log DB 43. .
That is, it is recorded with the digital signature A added by the secret key A in the game log recording program.

FIG. 4 is a diagram showing the flow of information in this game service. The flow of the game service will be described below with reference to FIG. In addition, prior to the start of the game service, the game content server 4
In 2, the signature verification is performed on the digital signature B added to the game log recording program with the public key B published by the game content provider, and after the validity of the game log recording program is confirmed, the game log is confirmed. The recording program is running.

A customer of a family restaurant or the like selects a desired game type and a prize from the game selection screen displayed on the display screen at the game terminal 44 installed in the store (S1). Then, the game start request including the terminal ID, the game ID, and the prize ID is transmitted from the game terminal 44 to the game content server 42 (S2). Upon receiving the game start request, the game content server 42 performs a settlement management ID issuance process, and sends the issued settlement management ID and the game price (amount) specified based on the game ID to the game terminal 44. Along with (S3), the payment management ID is encrypted and recorded in the game log DB 43 (S4). That is, the digital signature A with the secret key A known only to the provider embedded in the game recording program is added and recorded.

The user confirms the settlement management ID and the amount displayed on the game terminal 44, and inputs a confirmation operation (S5). Then, the terminal ID, the payment management ID, and the prize I
A game play confirmation notification including D and the amount of money (hereinafter collectively referred to as game information) is transmitted to the game content server 42 (S6), and when the game content server 42 receives this, the game content confirmation notification becomes a game play confirmation notification. The included game information is encrypted and recorded in the game log DB 43 as in the above (S7).

Then, the game sales request including the game information is transmitted to the POS system 32 (S8), and the game information is recorded in the POS sales DB 33 as sales information. Note that, here, the writing is performed in plain text.

Upon completion of writing the sales information, the POS system 32 sends a game sales approval to the game content server 42 (S10). The game content server 42 encrypts and records the game sales approval from the POS system 32 in the same manner as above (S11). Then, the game start approval notification is transmitted to the game terminal 44 (S
12) Upon receiving this notification, the game terminal 44 starts the game play (S13), and when the game play ends, the game result notification is transmitted to the game content server 42 (S14). In the game content server 42, the game result notification from the game terminal 44 is encrypted and recorded in the same manner as above (S15).

When the recording is finished, the game content server 42 sends a game result approval notice to the game terminal 44 (S16). On the game terminal 44, the payment management ID,
The acquired free gift name and free gift ID are printed, and one game operation ends (S17). If you want to play the game again,
The same processing is performed by returning to the game / prize selection (S1).

After the meal at the restaurant is completed, the customer can bring the print to the account, settle the meal fee and the game fee together at the restaurant, and receive the won prize.

In the user side processing system 31, the sales information of the game is managed by the POS system 32 as described above, and the game log with the digital signature is recorded in the game log DB 43. Then, the game content user regularly collects the game logs with the digital signature recorded in the game log DB 43 on a monthly basis, for example, on a monthly basis, and sells the network NET to the game management server 22 together with the sales report data created based on the POS sales DB 33.
Transfer through. In addition, the delivery of this game log with digital signature and sales report data can be done through the network NET.
Alternatively, the data may be recorded on a CD-R, an FD, or the like without using the medium, and may be recorded on a medium or the like.

The game management server 22, which has received the digitally signed game log and the sales report data, carries out a validity verification process.

FIG. 5 is a flow chart showing the flow of the validity verification process performed by the game management server. The game management server 22 verifies the signature of the digital signature A with the public key A for each digitally signed game log (S21), and verifies the validity of all game logs. If this verification is OK, first, the validity of the game log is guaranteed. Then, the game log and the sales report data are compared to determine a match (S22). If they match, the validity of the sales report data is guaranteed and the sales report data is correctly reported. You can check. On the other hand, if the verification is unsuccessful in step S21, it is detected that the game log has been tampered with, resulting in a game log tampering error (S24). If it is determined in step S22 that there is no match, the sales report data is tampered with. It is detected and a sales report data tampering error occurs (S2
5).

As described above, the game content provider provides the program itself for recording the game log with the alteration prevention means in addition to the game log.
It is possible to ensure the validity of the log data by the game log recording program. As a result, as described above, when the game system 41 is used in an environment isolated from the Internet such as a restaurant, it is checked whether the sales report data from the user is valid for the game content provider side. Therefore, it is possible to obtain a proper game fee.

Although the game log has been described here as an example of the data for which falsification is to be prevented, the data is not limited to this.

[0033]

As described above, according to the present invention, when data is recorded on the recording medium on the reporter side, a digital signature with the private key A known only to the recipient is added and recorded. , The legitimacy of this digital signature can be verified only by the recipient who holds the public key A, and if the data is falsified, the recipient who has the public key A can detect the fraudulent act. It is possible to prevent the data from being tampered with.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining a falsification prevention method according to an embodiment of the present invention.

FIG. 2 is a system configuration diagram to which the tampering prevention method according to the embodiment of the present invention is applied.

FIG. 3 is a diagram of a game service system configuration to which the tampering prevention method according to the embodiment of the present invention is applied.

4 is a diagram showing a flow of information transmission in the game service system of FIG.

FIG. 5 is a flowchart showing a flow of a validity verification process.

[Explanation of symbols]

1 Recipient side processing device 2 Program creation means 3 encryption means 4 Recipient side signature verification means 11 Reporter side processor 12 Reporter's signature verification means 13 Execution means 21 Provider side processing system 22 Game management server 23 Game Log DB 31 User side processing system 32 POS system 33 POS Sales DB 41 game system 42 Game Content Server 43 Game log DB 44 game terminals

   ─────────────────────────────────────────────────── ─── Continued front page    (54) [Title of Invention] Anti-tampering method, program, anti-tampering system, receiver side processing device, reporter side processing device, data                     Recording system, game service system with game log tampering prevention means, provider side processing device, and                     User side processor

Claims (14)

[Claims] 1. A receiver processing device on the data receiver side,
A method for preventing tampering of the data by the data reporter in a system configured with a reporter side processing device on a data reporter side for creating data to be passed to the recipient side processing device, The recipient-side processing device uses the secret key A known only to the recipient in the program including the process of recording the data on the recording medium.
And a program X including a digital signature process for adding a digital signature A by the secret key A in the program to the data and recording the data on a recording medium when the data is recorded according to the recording process. Created and installed in the reporter side processing device for use, and when the digitally signed data created based on the program X is received from the reporter, it is paired with the private key A. The signature verification is performed by using a certain public key A to verify the validity of the data, the reporter-side processing device installs and executes the program X, and writes the data to the recording medium according to the recording process of the program X. At the time of recording, a digital signature A by the secret key A in the program X is added to the data, the data is recorded on a recording medium, and the digital signature is added. A tampering prevention method characterized by passing data to the recipient. 2. A receiver processing device on the data receiver side,
A method for preventing tampering of the data by the data reporter in a system configured with a reporter side processing device on a data reporter side for creating data to be passed to the recipient side processing device, The recipient-side processing device uses the secret key A known only to the recipient in the program including the process of recording the data on the recording medium.
And a program X including a digital signature process for adding a digital signature A by the secret key A in the program and recording the data on a recording medium when the data is recorded according to the recording process. , And digital signature B with private key B known only to the recipient
Is added to create a digitally signed program X, which is installed in the reporter-side processing device and used.
When the digitally signed data is received from the reporter, the signature verification is performed with the public key A that is a pair with the private key A to verify the validity of the data. Installing the digitally signed program X, the digitally signed program X
The digital signature B added to the above is verified with the public key B which is a pair with the secret key B, and the program X
When the data is recorded on the recording medium according to the recording process of the program X, the digital signature A by the secret key A in the program X is added to the data. Falsification prevention method, characterized in that the data is recorded on a recording medium and the data with the digital signature is passed to the recipient. 3. When recording data for passing data to a data receiver by a computer on the side of the data reporter in order to prevent the data reporter from tampering with the data, the data is included in the program. Digital signature A by the private key A known only to the embedded data recipient
A program for functioning as a means for adding and recording. 4. A computer for preventing tampering of the program according to claim 3, wherein a digital signature B by a secret key B added to the program and known only to the data receiver is paired with the secret key B. A program for functioning as means for verifying with the public key B to verify the authenticity of the program. 5. A receiver processing device on the data receiver side,
A reporter-side processing device on the data reporter side for creating data to be passed to the recipient-side processing device, wherein the recipient-side processing device is within a program including a recording process for recording the data on a recording medium. , A secret key A known only to the recipient is embedded, and when data is recorded according to the recording process, a digital signature A by the secret key A in the program is added to the data and recorded on a recording medium. Program creating means for creating a program X including a digital signature process, and digitally signed data received from the reporter side processing device is subjected to signature verification by a public key A which is a pair with the private key A, and A receiver side signature verification means for verifying the legitimacy, and the reporter side processing device comprises an execution means for installing and executing the program X. When the data is recorded on the recording medium according to the recording process of the program X, the executing unit follows the digital signature process and applies the digital signature A by the secret key A embedded in the program to the data. A falsification prevention system characterized by adding and recording. 6. A receiver processing device on the data receiver side,
A reporter-side processing device on the data reporter side for creating data to be passed to the recipient-side processing device, wherein the recipient-side processing device is within a program including a recording process for recording the data on a recording medium. , A secret key A known only to the recipient is embedded, and when data is recorded according to the recording process, a digital signature A by the secret key A in the program is added to the data and recorded on a recording medium. Program creating means for creating a program X including a digital signature process, and a program X created by the program creating means with a digital signature B added with a digital signature B by a secret key B known only to the recipient. And a digital key with the digital signature received from the reporter-side processing device, the public key A being a pair with the private key A. Thus the signature verification performed, and a receiving side signature verifying means for verifying the validity of data, the reported side processor is to install the digital signed program X, the digital signed program X
The digital signature B added to the secret key B is verified with the public key B which is a pair with the private key B, and the authenticity is confirmed by the reporter side signature verification means, and then the digital signature B is verified. Executing means for executing the program X, the executing means, when recording the data on the recording medium according to the recording processing of the program X, executes the program within the program X according to the digital signature processing. A tampering prevention system characterized by adding a digital signature A with an embedded secret key A and recording it on a recording medium. 7. A receiver processing device on the data receiver side for receiving data from a data reporter, wherein the receiver processing device is within a program including a recording process for recording data on a recording medium, A digital key for embedding a secret key A known only to the recipient and adding a digital signature A by the secret key A in the program to the data when the data is recorded according to the recording process and recorded on a recording medium. Program creating means for creating a program X including signature processing; and a program with the program X installed in the reporter-side processing device and executed to receive the digitally-signed data from the reporter-side processing device. With respect to the digitally signed data, the signature verification is performed by the public key A which is a pair with the private key A, and the validity of the data is verified. Receiving side processing apparatus characterized by comprising a receiving side signature verification means proving. 8. A receiver processing device on the data receiver side for receiving data from a data reporter, wherein the receiver processing device is within a program including a recording process for recording data on a recording medium, A digital key for embedding a secret key A known only to the recipient and adding a digital signature A by the secret key A in the program to the data when the data is recorded according to the recording process and recorded on a recording medium. A program creating means for creating a program X including a signature process, and a program X created by the program creating means for creating a program X with a digital signature in which a digital signature B by a secret key B known only to the recipient is added The digital signature attaching program X is installed in the encryption means and the reporter side processing device, and the digital signature attaching program X is installed. Program X
The digital signature B added to the program X is subjected to signature verification with the public key B which is a pair with the private key B, and the program X
This program X is executed after the validity of
The digital-signature-added data created by the above is received from the reporter-side processing device, and the received digital-signature-added data is signature-verified by the public key A which is a pair with the secret key A, to verify the validity of the data. And a recipient-side signature verification means for performing the recipient-side processing. 9. A reporter-side processing device on the reporter side that creates data to be passed to a data receiver, wherein the reporter-side processing device has a secret key A that is known only to the recipient. The recording medium includes an executing means for executing the program X, and when the data is recorded on the recording medium according to the recording processing included in the program X, the executing means follows the digital signature processing included in the program X for the data. A reporter-side processing device characterized by adding and recording a digital signature A by a secret key A embedded in the program. 10. A reporter-side processing device on the reporter side for creating data to be passed to a data recipient, wherein the reporter-side processing device is a secret key B known only to the recipient.
The digital signature-provided program X with the digital signature B according to the above is received from the recipient, and the reporter-side signature verification means for verifying the signature of the digital-signed program X with the public key B paired with the private key B. And executing means for executing the program X after the authenticity is confirmed by the reporter side signature verifying means, and the executing means records data in a recording medium according to a recording process included in the program X. In doing so, according to the digital signature processing included in the program X, the digital signature A by the secret key A embedded in the program X is added to the data and recorded. Processing equipment. 11. A tampering prevention system according to claim 3 or 4, wherein the data is data related to sales, and the program is a program including processing for generating and recording data related to sales. Recording system. 12. A game content provider that provides a game service by installing a game terminal in a store on the side of a user whose sales are managed by the POS system. Based on the POS system, the provider side processing device for acquiring sales report data at the game terminal and the game terminal sales provided by the game content provider side are managed by the POS system, and the sales report at the game terminal is based on the POS system. A user-side processing device provided on the user side for creating data and delivering it to the game content provider, wherein the provider-side processing device includes a recording process for generating and recording a game log in the game terminal. To
A secret key A known only to the game content provider is embedded, and when a game log is recorded according to the recording process, a digital signature A based on the secret key A in the program is added to the game log and recorded on a recording medium. Program creating means for creating a program X including a digital signature process to be recorded, and a program with a digital signature in which the program X created by the program creating means is added with a digital signature B by a secret key B known only to the game content provider. A provider that verifies the authenticity of the game log by performing encryption signature verification on the digital signature-signed game log received from the user-side processing device by the public key A paired with the private key A. Side signature verification means and the sales report data acquired from the user side. And verification means for verifying the legitimacy of sales report data by comparing with the game log after signature verification by the provider-side signature verification means, and the user-side processing device installs the program X with digital signature. And the program X with the digital signature
With respect to the digital signature B added to, the user side signature verification means for verifying the signature with the public key B paired with the secret key B, and the legitimacy is confirmed by the user side signature verification means. And executing means for executing the program X, the executing means, when recording the game log at the game terminal on the recording medium according to the recording processing of the program X, according to the digital signature processing. On the other hand, with a game log tampering prevention means characterized by adding a digital signature A by the secret key A embedded in the program X and recording it as a game log with a digital signature to be passed to the user side processing device. Game service system. 13. A game content provider that provides a game service by installing a game terminal in a store on the side of a user whose sales are managed by the POS system, and is provided to the POS system from the user. A processing device on the provider side for acquiring sales report data on a game terminal based on the game, wherein the processing device on the provider side includes a recording process for generating and recording a game log in the game terminal on a recording medium, A secret key A known only to the content provider is embedded, and when a game log is recorded according to the recording process, a digital signature A by the secret key A in the program is added to the game log and recorded on a recording medium. A program creating means for creating a program X including a digital signature process; An encryption unit for creating a digital signature-provided program X by adding a digital signature B by a secret key B known only to the game content provider to the program X created by the RAM creating unit; and a user connected to the game terminal The digital-signature-added program X is installed in the side processing device, and the digital signature B added to the digital-signature-added program X is signature-verified with the public key B which is a pair with the private key B, so that the program X The digital-signature-added game log recorded on the recording medium by the program X, which is executed after confirming the legitimacy, is received from the user-side processing device, and the secret-key A for the received digital-signature-added game log. User side that verifies the validity of the game log by verifying the signature with public key A that is paired with A name verification means and a verification means for verifying the validity of the sales report data by comparing the sales report data acquired from the user side with a game log after signature verification by the user side signature verification means. A processing device on the provider side, which is provided. 14. A user-side processing device provided on a user side, wherein a game terminal provided by a game content provider is installed in its own store, and sales of the game terminal are paid to the game content provider. The user-side processing device receives from the game content provider a program X with a digital signature to which a digital signature B based on a secret key B known only to the game content provider is added, and installs the program X. A user side signature verification means for verifying a signature with the public key B paired with the secret key B; and an execution means for executing the program X after the validity is confirmed by the user side signature verification means. The executing means includes a recording medium on the recording medium according to a recording process included in the program X. When recording the game log on the game terminal, the digital signature A by the secret key A embedded in the program is added to the game log according to the digital signature processing included in the program X, and A user-side processing device characterized by being recorded as a game log with a digital signature to be passed to the user-side processing device.