Money trading systems, information terminals, computer programs, and money trading methods

Abstract

We provide a financial transaction system, computer program, and financial transaction method that enable secure financial transactions even offline. [Solution] The first information terminal 20 includes an encryption means 26 that encrypts transaction information, including transaction amount data, with the private key of the first information terminal 20; a monetary processing means 26 that increases or decreases first balance data based on the transaction amount data; and a first display means 26 that displays image information including the encrypted transaction information and the public key of the first information terminal 20. The second information terminal 10 includes a second image reading means 16 that reads the image information displayed by the first information terminal 20; a second acquisition means 16 that obtains encrypted transaction information and the public key of the first information terminal 20 from the image information; a decryption means 16 that decrypts the transaction information encrypted using the public key of the first information terminal 20; and a monetary processing means 16 that increases or decreases first balance data based on the transaction amount data included in the decrypted transaction information.

Description

Technical Field

[0001] The present invention relates to a money transaction system, an information terminal, a computer program, and a money transaction method capable of safely performing a money transaction based on money data such as electronic money between two terminals even in an offline state.

Background Art

[0002] Conventionally, in an environment where an information terminal such as a smartphone carried by a purchaser and an information terminal held by a seller can both be connected to a money transaction server via a network, the information terminal of the purchaser and the information terminal of the seller access the server respectively, so that a money transaction system capable of executing a money payment process based on money data between the information terminal of the purchaser and the information terminal of the seller has been disclosed (for example, Patent Document 1). However, the money transaction system of Patent Document 1 executes a money transaction between two information terminals via a server in an environment where network communication is possible, and it was not possible to perform a money transaction in an offline environment. Therefore, the applicant has proposed a technology (hereinafter, an offline money transaction system) capable of executing a money transaction based on money data between two information terminals by using an information code even in an offline environment (for example, Patent Document 2). Even in such an offline money transaction system, since an exchange of money data occurs as in the money transaction system in an online environment, it is necessary to strengthen security. The applicant has applied for a patent regarding a technology for strengthening the security of a money transaction by comparing the identification information of two information terminals that perform a money transaction so that a third party not related to the money transaction does not steal the information code and improperly夺取 the money data, and by using a time stamp.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] Security measures in offline monetary transaction systems include not only preventing malicious third parties from stealing transaction data and gaining illegal profits, but also preventing malicious parties (buyers or sellers) from tampering with transaction data and gaining illegal profits. However, until now, no measures have been presented to prevent the tampering of transaction data in offline monetary transaction systems.

[0005] The present invention aims to provide a financial transaction system, information terminal, computer program, and financial transaction method that enable secure financial transactions based on financial data between two information terminals, even in environments where a network is unavailable. [Means for solving the problem]

[0006] The present invention is essentially a monetary transaction system as described in (1) or (2) below. (1) A money transaction system that performs money transactions offline based on money data between the first information terminal and the second information terminal, comprising a first information terminal having a first image display unit and a first image reading unit, and a second information terminal having a second image display unit and a second image reading unit, wherein the first information terminal includes a first storage means for storing first balance data held by the first information terminal and a private key and a public key of the first information terminal, a first acquisition means for acquiring transaction amount data in the money transaction, an encryption means for encrypting transaction information including the transaction amount data acquired by the first acquisition means with the private key of the first information terminal, and a money processing that increases or decreases the first balance data based on the transaction amount data acquired by the first acquisition means. A money transaction system comprising: a means; a first display means for displaying image information including the encrypted transaction information and the public key of the first information terminal on the first image display unit; the second information terminal comprising: a second storage means for storing second balance data held by the second information terminal; a second image reading means for causing the second image reading unit to read the image information displayed by the first information terminal; a second acquisition means for obtaining the encrypted transaction information and the public key of the first information terminal from the image information; a decryption means for decrypting the encrypted transaction information using the public key of the first information terminal; and a money processing means for increasing or decreasing the second balance data based on the transaction amount data included in the transaction information decrypted by the decryption means. (2) The money transaction system described in (1) above, wherein the second information terminal stores the transaction information in an encrypted state. (3) The money transaction system according to (1) above, wherein the second information terminal stores the private key and public key of the second information terminal in the second storage means, the second information terminal further comprises: a second encryption means for encrypting the transaction information obtained from the first information terminal with the private key of the second information terminal; and a second display means for displaying image information including the transaction information encrypted by the second encryption means and the public key of the second information terminal on the second image display unit. Furthermore, the present invention is essentially based on the information terminal described in (4) below. (4) An information terminal in a money transaction system that performs money transactions offline based on money data between a first information terminal and a second information terminal, the first information terminal comprising: a first storage means for storing first balance data held by the first information terminal and a private key and a public key of the first information terminal; a first acquisition means for acquiring transaction amount data in the money transaction; an encryption means for encrypting transaction information including the transaction amount data acquired by the first acquisition means with the private key of the first information terminal; a money processing means for increasing or decreasing the first balance data based on the transaction amount data acquired by the first acquisition means; and a first display means for displaying image information including the encrypted transaction information and the public key of the first information terminal. Furthermore, the present invention is essentially an information terminal as described in (5) or (6) below. (5) A financial transaction system that performs financial transactions offline based on financial data between a first information terminal and a second information terminal, the second information terminal having means for displaying image information including transaction information including transaction amount data encrypted with the private key of the first information terminal and the public key of the first information terminal for decrypting the encrypted transaction information, the second information terminal having a second storage means for storing second balance data held by the second information terminal, a second image reading means for reading the image information displayed by the first information terminal, a second acquisition means for obtaining the encrypted transaction information and the public key of the first information terminal from the image information, a decryption means for decrypting the encrypted transaction information using the public key of the first information terminal, and a financial processing means for increasing or decreasing the first balance data based on the transaction amount data included in the transaction information decrypted by the decryption means. (6) The information terminal described in (5) above, which stores the transaction information in an encrypted state. In addition, the present invention is characterized by the server described in (7) below. (7) A server capable of communicating with the information terminal described in (4) above and the information terminal described in (5) or (6) above, comprising: a server storage unit that stores the first balance data and / or the second balance data as server balance data; and an update unit that acquires the first balance data and / or the second balance data from the first information terminal or the second information terminal as terminal balance data, acquires the transaction information, and updates the server balance data stored in the server storage unit based on the acquired terminal balance data and the transaction information. In addition, the present invention is essentially a computer program as described in any of (8) to (10) below. (8) A money transaction system having a first information terminal having a first image display unit and a first image reading unit, and a second information terminal having a second image display unit and a second image reading unit, which performs money transactions between the first information terminal and the second information terminal offline based on money data, wherein the computer program executed by the first information terminal has the following functions: a function to store first balance data held by the first information terminal and the private key and public key of the first information terminal; a function to acquire transaction amount data in the money transaction; a function to encrypt transaction information including the acquired transaction amount data with the private key of the first information terminal; a function to increase or decrease the first balance data based on the acquired transaction amount data; and a function to display image information including the encrypted transaction information and the public key of the first information terminal. (9) A money transaction system that performs money transactions offline based on money data between the first information terminal and the second information terminal, comprising a first information terminal having a first image display unit and a first image reading unit, wherein the computer program executed by the second information terminal is a computer program that includes, the first information terminal having means for displaying image information including transaction information including transaction amount data encrypted with the private key of the first information terminal and the public key of the first information terminal, and the computer program of the second information terminal having a function for storing second balance data held by the second information terminal, a function for causing the second image reading unit to read the image information displayed by the first information terminal, a function for obtaining the encrypted transaction information and the public key of the first information terminal from the image information, a function for decrypting the encrypted transaction information using the public key of the first information terminal, and a function for increasing or decreasing the second balance data based on the transaction amount data included in the decrypted transaction information. (10) The computer program described in (9) above, further having a function to store the transaction information in an encrypted state. Furthermore, the present invention is essentially a monetary transaction method as described in (11) or (12) below. (11) A computer program having a function to display image information including the encrypted transaction information and the public key of the first information terminal, when performing a monetary transaction based on monetary data between the first information terminal and the second information terminal offline using a first information terminal having a first image display unit and a first image reading unit, the first information terminal storing first balance data held by the first information terminal and the private key and public key of the first information terminal, acquiring transaction amount data in the monetary transaction, encrypting transaction information including the acquired transaction amount data with the private key of the first information terminal, increasing or decreasing the first balance data based on the acquired transaction amount data. (12) A method for conducting a monetary transaction offline between a first information terminal and a second information terminal, using a first information terminal having a first image display unit and a first image reading unit, and a second information terminal having a second image display unit and a second image reading unit, wherein the first information terminal has means for displaying image information including transaction information including transaction amount data encrypted with the private key of the first information terminal and the public key of the first information terminal, the second information terminal stores second balance data held by the second information terminal, the second image reading unit reads the image information displayed by the first information terminal, obtains the encrypted transaction information and the public key of the first information terminal from the image information, decrypts the encrypted transaction information using the public key of the first information terminal, and increases or decreases the second balance data based on the transaction amount data contained in the decrypted transaction information. [Effects of the Invention]

[0007] According to the present invention, even in environments where a network is unavailable, monetary transactions based on financial data can be securely executed between two information terminals. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the configuration of the money transaction system according to this embodiment. [Figure 2] This diagram illustrates a usage scenario for the money transaction system according to this embodiment. [Figure 3] This is a block diagram of the seller's terminal and the buyer's terminal according to this embodiment. [Figure 4] This is a diagram illustrating the information code according to this embodiment. [Figure 5] This is a diagram illustrating the information contained in the information code stored in the memory unit. [Figure 6] This diagram shows the transaction screen displayed on the seller's terminal. [Figure 7]It is a diagram showing a charge screen displayed on the purchaser's terminal. [Figure 8] It is a diagram showing a payment screen displayed on the purchaser's terminal. [Figure 9] It is a diagram showing a payment completion screen displayed on the purchaser's terminal. [Figure 10] It is a flowchart (Part 1) showing the offline money transaction process according to this embodiment. [Figure 11] It is a flowchart (Part 2) showing the offline money transaction process according to this embodiment.

Embodiment for Carrying out the Invention

[0009] An embodiment of a money transaction system according to the present invention will be described based on the drawings. FIG. 1 is a diagram showing the configuration of a money transaction system 1 according to this embodiment, and FIG. 2 is a diagram for explaining the usage scenario of the money transaction system 1 according to this embodiment. As shown in FIGS. 1 and 2, the money transaction system 1 according to this embodiment includes information terminals 10 and 20 carried by two persons who conduct a money transaction, respectively, and a server 30. As shown in FIG. 1, in an environment where network communication using an Internet line 2 or the like is available, the information terminals 10 and 20 and the server 30 can exchange information with each other by wireless communication or wired communication. On the other hand, in this embodiment, as shown in FIG. 2, even in an environment where network communication cannot be used, it is possible to conduct a money transaction based on electronic money using the two information terminals 10 and 20.

[0010] In this embodiment, a scene will be exemplified and described in which a purchaser purchases a product from a seller, and the financial transaction arising from the purchase of the product is conducted using the information terminal 10 on the seller side (corresponding to the second information terminal of the present invention) and the information terminal 20 on the purchaser side (corresponding to the first information terminal of the present invention). Here, the information terminal 10 carried by the seller is also referred to as the seller-side terminal 10, and the information terminal 20 carried by the purchaser is also referred to as the purchaser-side terminal 20. However, the financial transaction system 1 according to this embodiment is not only used at the time of purchasing a product. For example, it can also be used for calculating the bill at a dinner, settling the group travel expenses among members, collecting money in a lump sum such as for a campaign, sending money to family members, paying a thank-you gift, etc. Also, in the examples shown in FIGS. 1 and 2, a scene where there is a one-to-one relationship between the seller who receives electronic money and the purchaser who pays electronic money is exemplified, but it is not limited to this configuration. For example, a configuration can be adopted in which one person (for example, the organizer of the dinner bill) receives electronic money from a plurality of persons (for example, a plurality of participants in the dinner bill).

[0011] FIG. 3 is a block diagram showing the configurations of the seller-side terminal 10 and the purchaser-side terminal 20. The seller-side terminal 10 is an information terminal such as a smartphone, tablet, or notebook computer carried by the seller. As shown in FIG. 3, it has a camera 11, a communication unit 12, a display 13, an input unit 14, a storage unit 15, and an arithmetic unit 16. The camera 11 reads an information code displayed on the purchaser-side terminal 20, etc. The communication unit 12 communicates with the server 30 in an environment where network communication is available. The display 13 displays an information code 40, etc., including transaction information of the financial transaction such as the transaction amount, on the screen. The input unit 14 is used by the seller to input transaction information such as the transaction amount. Note that a configuration using a touch display in which the display 13 and the input unit 14 are integrated can be adopted.

[0012] Here, the information code 40 according to this embodiment will be described. Figure 4 is a diagram showing an example of the information code 40 in this embodiment. In this embodiment, the information code 40 is a matrix-type two-dimensional code, and an example configuration using a color QR code composed of information cells of three or more colors is shown, but it is not limited to this configuration, and a QR code (registered trademark) composed of white and black information cells arranged in a grid may also be used.

[0013] As shown in Figure 4, the information code 40 according to this embodiment is a rectangular two-dimensional code comprising an information code area 401 composed of two or more colored information cells 402 that serve as units for displaying information, a teacher code area 403 having teacher cells 404 that are the same color as the information cells 402 and have the same number of colors as the information cells 402 in order to identify the colors of the information cells 402, and a cutout symbol 405.

[0014] In particular, the information code 40 according to this embodiment has multiple teacher cells 404 in the teacher code area 403 in order to improve the accuracy of identifying the color of the information cell 402. The types of colors of the teacher cells 404 and the types of colors of the information cell 402 match, and by comparing the colors of the teacher cells 404 and the information cell 402, it is possible to identify the color of the information cell 402 with high accuracy. In particular, in color QR codes, as the number of colors increases, the hues of each color become closer, so it may be difficult to appropriately identify the color of the information cell 402 depending on the lighting environment, the printing environment of the information code 40, the display environment of the information code 40 on a display, etc., and the fading of the printed information code 40 over time. Even in such cases, by referring to the teacher cells 404 and identifying the color of the information cell 402, the information in the information cell 402 can be appropriately grasped. For example, if the color information of information cell 402 is purplish and it is difficult to determine whether it is similar to red or blue, then if the color information is closer to red than the color information of the purple training cell 404, then the color of information cell 402 can be determined to be red. Note that color information can be quantified as RGB or CMY values.

[0015] The information code area 401 can record specific information consisting of a certain amount of character information and / or binary information by changing the display pattern of the information cell 402, which is an information unit. The content of the specific information recorded in the information code area 401 is not particularly limited, but in this embodiment, it includes the identification information of the seller's terminal 10 (hereinafter also referred to as the seller's terminal PID), the identification information of the buyer's terminal 20 (hereinafter also referred to as the buyer's terminal PID), the product name, transaction amount, quantity, subject of the transaction, transaction date and time, and other transaction information necessary for monetary transactions between the seller and the buyer. The seller's terminal PID is identification information such as the seller code, the seller's mobile phone number, and the product identification number of the seller's terminal 10 (MAC address or IMEI number) to identify the seller, and similarly, the buyer's terminal PID is identification information such as the buyer code, the buyer's mobile phone number, and the product identification number of the buyer's terminal 20 (MAC address or IMEI number) to identify the buyer. In addition to the information mentioned above, transaction information can also include transaction codes (for example, unique numbers such as epoch seconds or sequential numbers under certain control) and timestamps.

[0016] Furthermore, in this embodiment, as will be described later, the information code 40 includes one of the following information at the time the information code 40 is presented: information indicating the start of a transaction, information indicating that payment of money has been completed, information indicating that money has been received, or information indicating that the monetary transaction is being canceled. In the following, the information code containing information indicating the start of a transaction will be referred to as the transaction start information code 41, the information code containing information indicating that payment of money has been completed will be referred to as the payment completion information code 42, the information code containing information indicating that money has been received will be referred to as the receipt information code 43, and the information code containing information indicating that the monetary transaction is being canceled will be referred to as the cancellation information code 44, and these information codes 41 to 44 will be collectively referred to as the information code 40.

[0017] Furthermore, information code 40 may include personal information, including biometric information for biometric authentication. In addition to biometric information, personal information may include information such as mobile phone number, My Number, passport number, account number, driver's license number, name, social security number, date of birth, place of birth, and maiden name. Biometric information may include facial image, fingerprint information, iris information, palm print, retina, blood vessels, voice, and ear print.

[0018] In this embodiment, the information code 40, in which specific information is recorded, is composed of three or more information cells 402, and can store a larger amount of information compared to an information code composed of only two colors, white and black. However, since the data capacity that can be stored in the information code 40 is smaller than that of other recording media, if an image of the entire face is recorded with a resolution sufficient for facial recognition, the storage capacity of the information code area 401, which is composed of four information cells 402, may become insufficient. Therefore, in this embodiment, the information code 40 can store a facial image for facial recognition by storing only a part of the face that is a characteristic point in facial recognition, such as the eyes or mouth, rather than the entire face of the user, as the facial image for facial recognition.

[0019] The storage unit 15 stores a program for performing monetary transactions according to this embodiment, as well as an information code 40 that includes balance data of electronic money used for offline monetary transactions, and transaction information used in monetary transactions. In this embodiment, the program stored in the storage unit 15 is stored in a state that prevents reverse engineering or modification of the program itself through techniques such as obfuscation (for example, converting names in the source code such as class names, method names, and variable names to names that are difficult for humans to read, encrypting strings containing functions, and inserting meaningless loops or Goto statements to make the source code difficult to understand) and encryption. As a result, in this embodiment, it is possible to effectively prevent the seller from illegally modifying the program on the seller's terminal 10.

[0020] Furthermore, in this embodiment, the information code 40 stored in the storage unit 15 is also stored in an encrypted state to prevent data tampering. Here, Figure 5 is a diagram illustrating the information contained in the information code 40 stored in the storage unit 15. As shown in Figure 5, the information code 40 stored in the storage unit 15 includes transaction information such as the seller's terminal PID, the buyer's terminal PID, product name, transaction amount, quantity, transaction title, and transaction date and time, but this transaction information is encrypted by the buyer's terminal 20's private key KS20 (however, the transaction start information code 41 does not include the buyer's terminal PID). Furthermore, as shown in Figure 5, the information code 40 stored in the storage unit 15 includes the public key KP20 of the buyer's terminal 20 in addition to the encrypted transaction information. The buyer's public key KP20 is stored in unencrypted plaintext. As a result, in this embodiment, the seller's terminal 10 can use the buyer's public key KP20 contained in the information code 40 stored in the storage unit 15 to decrypt and use the encrypted transaction information also contained in the information code 40. In addition, since the transaction information contained in the information code 40 stored in the storage unit 15 is encrypted, the stored transaction information itself cannot be tampered with.

[0021] The memory unit 15 can be configured to store the information code 40 as image information, or it can be configured to store binary data read from the information code 40. When the information code 40 is stored as image information, the encrypted transaction information contained in the information code 40 and the buyer's public key KP20 can be read from the image information.

[0022] The arithmetic unit 16 executes a program stored in the storage unit 15 to implement a seller-side transaction function that performs electronic money transactions offline, and a balance data update function that updates the server balance data stored in the server 30 so that the terminal balance data stored in the seller-side terminal 10 matches the server balance data of the seller-side terminal 10 stored in the server 30, in an environment where network communication is available. The above program can be executed in application or app format on the seller-side terminal 10. The functions of the seller-side terminal 10 are described below.

[0023] The seller-side transaction function of the seller-side terminal 10 generates a transaction start information code 41 containing transaction information, as shown in Figure 6, when the seller inputs the transaction amount via the input unit 14 or scans a barcode printed on the product with the camera 11, and displays the generated transaction start information code 41 along with the input transaction amount on the display 13. In this embodiment, the buyer-side terminal 20 reads the transaction start information code 41 displayed by the seller-side terminal 10 to execute the electronic money payment. In this embodiment, the seller-side transaction function can also be configured to similarly generate a receipt information code 43 and a cancellation information code 44 containing transaction information and display them on the display 13.

[0024] Furthermore, in this embodiment, when payment is executed on the buyer's terminal 20, a payment completion information code 42 (payment completion image information) indicating the completion of payment is displayed on the display 23 of the buyer's terminal 20. In this case, the seller's transaction function reads the payment completion information code 42 displayed on the buyer's terminal 20 with the camera 11 and increases the terminal balance data of the electronic money stored in the storage unit 15 according to the transaction amount. Specifically, in this embodiment, the payment completion information code 42 includes transaction information encrypted with the buyer's terminal 20's private key KS20 and the buyer's terminal 20's public key KP20. The seller's transaction function decrypts the encrypted transaction information contained in the payment completion information code 42 using the buyer's public key KP20, which is also contained in the payment completion information code 42, and can increase the terminal balance data of the electronic money stored in the storage unit 15 using the transaction amount data contained in the decrypted transaction information. In this way, the seller terminal 10 can read the payment completion information code 42 displayed on the buyer terminal 20, allowing it to confirm that payment has been completed on the buyer terminal 20, even when conducting electronic money-based financial transactions offline, and enabling the seller terminal 10 to properly complete the transaction.

[0025] The balance data update function of the seller terminal 10 updates the server balance data stored in the server 30 to match the electronic money terminal balance data stored in the seller terminal 10, in an environment where network communication such as the internet line 2 is available. In other words, in this embodiment, when the seller terminal 10 and the buyer terminal 20 are in an environment where network communication such as the internet line 2 is available, they can conduct monetary transactions based on electronic money via the server 30 as in the conventional method, and the balance data of the seller carrying the seller terminal 10 is stored in the server 30 as server balance data. On the other hand, in an environment where network communication is not available, the seller terminal 10 cannot access the server 30, so when an offline monetary transaction according to this embodiment is performed, the terminal balance data stored in the storage unit 15 of the seller terminal 10 and the server balance data stored in the server 30 will no longer match. Therefore, the balance data update function accesses the server 30 when an offline monetary transaction has taken place and network communication is available, and updates the server balance data stored in the server 30 to match the terminal balance data stored in the seller terminal 10.

[0026] The buyer's terminal 20 is an information terminal such as a smartphone, tablet, or laptop carried by the buyer, and as shown in Figure 3, it has a camera 21, a communication unit 22, a display 23, an input unit 24, a storage unit 25, and a processing unit 26. The camera 21 reads information codes 40, including transaction information, displayed on the seller's terminal 10. The communication unit 22 communicates with the server 30 in an environment where network communication is available. The display 23 displays payment completion information codes 42, etc., on the screen, indicating that payment has been completed. The input unit 24 is used by the buyer to input payment information, etc. Note that a configuration using a touch display in which the display 23 and the input unit 24 are integrated can be used.

[0027] Furthermore, the storage unit 25 stores a program for conducting monetary transactions according to this embodiment, as well as an information code 40 that includes electronic money balance data and transaction information used in monetary transactions. In this embodiment, the program stored in the storage unit 25 is stored in a state that prevents reverse engineering or modification of the program itself through methods such as obfuscation and encryption. This effectively prevents the purchaser from illegally modifying the program on the purchaser's terminal 20.

[0028] Furthermore, in this embodiment, the information code 40 stored in the storage unit 25 is also stored in an encrypted state to prevent data tampering. That is, the information code 40 stored in the storage unit 25, like the information code 40 stored in the storage unit 15 of the seller terminal 10, includes transaction information such as the seller terminal PID, buyer terminal PID, product name, transaction amount, quantity, transaction subject, and transaction date and time in an encrypted state, as shown in Figure 5, and also includes the seller's public key KP10 in unencrypted plaintext. In this embodiment, since the transaction information included in the information code 40 is encrypted, it is possible to effectively prevent the buyer from illegally altering the transaction information stored in the buyer terminal 20.

[0029] Furthermore, the arithmetic unit 26 executes a program stored in the storage unit 25 to realize a charging function that charges electronic money in an environment where network communication is available, and a buyer-side transaction function that performs monetary transactions based on electronic money offline. The above program can be executed in application or app format on the buyer-side terminal 20. The functions of the buyer-side terminal 20 are described below.

[0030] The charge function of the buyer's terminal 20 accesses the server 30 in an environment where network communication is available to charge electronic money. The charge function can be performed using a known method. For example, when charging electronic money via credit card payment, the charge function displays a screen on the display 13 for the buyer to enter the amount to be charged, as shown in Figure 7(A). When the buyer enters the charge amount, a charge confirmation screen is displayed, as shown in Figure 7(B). Upon the buyer's approval of the charge, the terminal accesses the server 30, and the terminal balance data stored in the buyer's terminal 20 is updated according to the charge amount.

[0031] The buyer-side transaction function of the buyer-side terminal 20 executes payment for the monetary transaction based on the transaction start information code 41, which includes the transaction information displayed by the seller-side terminal 10. Specifically, when the buyer-side transaction function reads the transaction start information code 41, which includes the transaction information displayed by the seller-side terminal 10, it extracts encrypted transaction information and the seller's public key KP10 from the transaction start information code 41. The buyer-side transaction function then decrypts the encrypted transaction information using the seller's public key KP10. Then, as shown in Figure 8(A), for example, the buyer-side transaction function displays the transaction amount included in the decrypted transaction information, as well as the balance stored in the storage unit 25 and the balance after payment, on the screen of the display 13. The buyer-side transaction function also displays a payment button on the screen and requests approval for payment of the transaction. Then, when the buyer presses the payment button, the buyer-side transaction function displays a payment confirmation as shown in Figure 8(B). When the buyer touches "Yes" to approve the payment, the buyer-side transaction function deducts the transaction amount from the terminal balance data stored in the memory unit 25 of the buyer-side terminal 20 and completes the payment. If the transaction amount is greater than the balance in the terminal balance data, the buyer-side transaction function will indicate that the transaction cannot be executed and will display an error on the screen of the display 13 (or it may display a message that prevents the payment button from being pressed).

[0032] Furthermore, when the buyer-side transaction function of the buyer-side terminal 20 completes payment, it generates a payment completion information code 42 indicating payment completion, and displays the generated payment completion information code 42 on the display 23, as shown in Figure 9. The payment completion information code 42 includes transaction information encrypted with the buyer-side terminal 20's private key KS20 and the buyer-side terminal 20's public key KP20, as shown in Figure 5. The payment completion information code 42 also includes information indicating that payment of monetary data corresponding to the transaction amount has been completed in the buyer-side terminal 20.

[0033] When payment is completed on the buyer's terminal 20, a payment completion information code 42 is displayed on the display 23, and the seller's terminal 10 is made to read the information code 42 indicating payment completion. This makes it possible for the seller's terminal 10 to confirm the completion of payment even in offline monetary transactions. In conventional online monetary transactions, the seller's terminal 10 can confirm that payment has been completed on the buyer's terminal 20 via the server 30. However, in offline monetary transactions, the seller's terminal 10 cannot access the server 30 to confirm whether payment has been completed on the buyer's terminal 20. Therefore, in this embodiment, by displaying a payment completion information code 42 indicating payment completion on the buyer's terminal 20, it is possible for the seller's terminal 10 to confirm the completion of payment even in an offline environment.

[0034] In this embodiment, personal information such as the seller's and buyer's account numbers, My Number (social security number), and biometric authentication information such as facial images is pre-stored in the storage units 15 and 25 of the seller's terminal 10 and the buyer's terminal 20. In this embodiment, the storage units 15 and 25 of the seller's terminal 10 and the buyer's terminal 20 each store terminal balance data held by the seller's terminal 10 and the buyer's terminal 20, respectively. It is preferable to encrypt the terminal balance data stored in the storage units 15 and 25 from the viewpoint of ensuring security. For example, the key string representing the terminal balance data can be converted by a predetermined function f(x) and then encrypted using RSA encryption. Furthermore, measures to make the disassembly of the program difficult to decipher are also effective in further enhancing security. It is also effective to periodically change the program.

[0035] Server 30 is installed on the internet line 2 and has the function of exchanging data with the seller terminal 10 and the buyer terminal 20 and performing electronic payments when the seller terminal 10 and the buyer terminal 20 can connect to the internet line 2. Furthermore, as described above, Server 30 stores the balance data of the seller terminal 10 and the buyer terminal 20 as server balance data, and can perform an update process to match the server balance data with the terminal balance data if the terminal balance data of the seller terminal 10 and the buyer terminal 20 do not match due to an offline monetary transaction. When performing the update process, in order to prevent fraud, the server can be configured to refer to the transaction code, etc., and check whether the amount increased at the seller terminal 10 and the amount decreased at the buyer terminal 20 match in the monetary transaction between the seller terminal 10 and the buyer terminal 20.

[0036] Next, the offline money transaction processing according to this embodiment will be described. Figures 10 and 11 are flowcharts of the offline money transaction processing according to this embodiment. In the offline money transaction processing shown in Figures 10 and 11, it will be explained that the buyer's terminal 20 has already charged and holds enough electronic money to cover the transaction amount in an environment where network communication such as the internet is available. Furthermore, in the following, the seller's terminal 10 will be described as a mobile terminal with telephone call functionality, such as a smartphone, and will store a seller's terminal PID in the storage unit 15 to identify the seller's terminal 10 itself. Similarly, the buyer's terminal 20 will also be described as a mobile terminal with telephone call functionality, such as a smartphone, and will store a buyer's terminal PID in the storage unit 25 as information to identify the buyer's terminal 20 itself.

[0037] In step S101, user authentication is performed on both the seller terminal 10 and the buyer terminal 20. For example, in this embodiment, when an application or app is launched on the seller terminal 10 and the buyer terminal 20, the cameras 11 and 21 first read a facial image and perform facial authentication. The method of facial authentication is not particularly limited, and known methods can be used. The facial information necessary for facial authentication can be captured in advance by the cameras 11 and 21 and stored in the storage units 15 and 25. Then, in step S102, it is determined whether facial authentication was successful on both the seller terminal 10 and the buyer terminal 20. If facial authentication is successful on both the seller terminal 10 and the buyer terminal 20, the process proceeds to step S103. On the other hand, if facial authentication fails on either the seller terminal 10 or the buyer terminal 20, the offline money transaction process shown in Figure 10 cannot be continued, and in step S124, an error message is displayed, and the offline money transaction process ends.

[0038] In step S103, the seller-side transaction function of the seller-side terminal 10 acquires transaction information, including the transaction amount of a monetary transaction. For example, the seller can scan the barcode of a product or manually enter the transaction amount, etc., to input transaction information such as the product name, transaction amount, quantity, transaction title, and transaction date and time of the product to be sold to the buyer into the input unit 14, thereby enabling the seller-side transaction function to acquire this transaction information. Alternatively, the seller-side transaction function can be configured to display a screen on the display 13 prompting the seller to input transaction information, allowing the seller to input the transaction information via the input unit 14, and then acquiring the transaction information entered by the seller.

[0039] In step S104, the seller-side transaction function of the seller-side terminal 10 encrypts the transaction information. Specifically, the seller-side transaction function of the seller-side terminal 10 encrypts the seller-side terminal PID stored in the memory unit 15 and the transaction information obtained in step S103 using the seller's private key KS10, which is also stored in the memory unit 15. The encryption method is not particularly limited, and a known public-key cryptography method can be used. Also, in step S104, since the seller-side transaction function has not obtained the buyer-side terminal PID, it encrypts the transaction information shown in Figure 5, excluding the buyer-side terminal PID.

[0040] In step S105, the seller-side transaction function of the seller-side terminal 10 generates and displays a transaction start information code 41 (transaction start image information) which includes encrypted transaction information and the seller's public key KP10. Specifically, the seller-side transaction function retrieves the seller's public key KP10 stored in the storage unit 15 and generates a transaction start information code 41 which includes the transaction information encrypted in step S104, the seller's public key KP10 obtained from the storage unit 15, and information indicating the start of a monetary transaction. Then, as shown in Figure 6, the seller-side transaction function displays the generated transaction start information code 41 on the display 13. In this embodiment, as shown in Figure 4, a color QR code is generated and displayed as the transaction start information code 41, but a known method can be used to generate the color QR code.

[0041] In step S106, the buyer-side transaction function of the buyer-side terminal 20 reads the transaction start information code 41 displayed on the seller-side terminal 10 in step S105 and stores it in the storage unit 25. Specifically, the buyer-side transaction function activates the camera 21 and displays a message prompting the buyer to read the transaction start information code 41 displayed on the seller-side terminal 10. When the buyer captures an image of the transaction start information code 41 displayed on the seller-side terminal 10 with the camera 21, the buyer-side transaction function extracts encrypted transaction information and the seller's public key KP10 from the image data of the read transaction start information code 41. The buyer-side transaction function then stores the acquired encrypted transaction information and the seller's public key KP10 in the storage unit 25.

[0042] In step S107, the buyer-side transaction function of the buyer-side terminal 20 decrypts the encrypted transaction information extracted in step S106 using the seller's public key KP10, which was also extracted in step S106. This allows the buyer-side terminal 20 to use the decrypted transaction information for display and balance data calculations.

[0043] In step S108, payment authorization is performed by the buyer's terminal 20. For example, as shown in Figure 8(A), the buyer's transaction function of the buyer's terminal 20 displays on the display 23 a screen showing the transaction amount included in the transaction information decrypted in step S107, terminal balance data and balance after payment stored in the buyer's terminal 20, and a payment button. When the buyer presses the payment button displayed on the display 23, the buyer's transaction function displays a message requesting payment authorization on the screen, as shown in Figure 8(B). If the buyer then instructs to authorize the payment via the input unit 24, payment authorization is performed on the buyer's terminal 20.

[0044] In step S109, since the payment has been approved, the buyer-side transaction function of the buyer-side terminal 20 reduces the electronic money balance data. For example, as shown in Figures 8(A) and (B), if the electronic money terminal balance data is 10,000 yen and the payment (transaction amount) is 2,800 yen, the buyer-side transaction function reduces the electronic money terminal balance data from 10,000 yen by 2,800 yen and updates the terminal balance data to 7,200 yen.

[0045] In step S110, the transaction information is encrypted by the buyer-side transaction function of the buyer-side terminal 20. Specifically, the buyer-side transaction function adds the buyer-side terminal 20's identification information (buyer-side terminal PID), which is stored in the buyer-side terminal 20's storage unit 25, to the transaction information decrypted by the buyer-side terminal 20 in step S107, and then encrypts this transaction information with the buyer's private key KS20, which is also stored in the storage unit 25. As with step S104, the encryption method is not limited, and known public-key cryptography methods can be used.

[0046] In step S111, the buyer-side transaction function of the buyer-side terminal 20 creates and displays the payment completion information code 42. Specifically, the buyer-side transaction function retrieves the buyer's public key KP20 stored in the memory unit 25. The buyer-side transaction function then generates a payment completion information code 42 (payment completion image information) which includes the transaction information encrypted in step S110, the buyer's public key KP20 retrieved from the memory unit 25, and information indicating that payment has been completed, and displays it on the display 23.

[0047] Moving on to Figure 11, in step S112, the seller-side transaction function of the seller-side terminal 10 determines whether or not the current monetary transaction has been canceled. For example, from step S103 onwards, the seller-side terminal 10 can display a button on the display 23 to cancel the current monetary transaction, and when the seller clicks this button, it can be determined that the current monetary transaction has been canceled. If the current monetary transaction has been canceled, the process proceeds to step S121; on the other hand, if the current monetary transaction has not been canceled, the process proceeds to step S113. Note that the process in step S112 can also be configured to be executed by the buyer-side transaction function of the buyer-side terminal 20.

[0048] In step S113, the seller-side transaction function of the seller-side terminal 10 reads the payment completion information code 42 displayed on the display 23 of the buyer-side terminal 20 in step S111 and stores it in the storage unit 15. In step S114, the seller-side transaction function of the seller-side terminal 10 decrypts the encrypted transaction information contained in the payment completion information code 42 read in step S113 using the buyer's public key KP20, which is also contained in the payment completion information code 42. This allows the seller-side terminal 10 to obtain the decrypted transaction information from the payment completion information code 42 displayed on the buyer-side terminal 20.

[0049] In step S115, the seller-side transaction function of the seller-side terminal 10 compares the transaction information stored in the seller-side terminal 10 with the transaction information contained in the payment completion information code 42 displayed on the buyer-side terminal 20 to see if they match. Then, in step S116, if it is determined that the transaction information matches, the process proceeds to step S117. On the other hand, if it is determined that the transaction information does not match, the process proceeds to step S124, where an error message such as "This is a different transaction. Please check the transaction items and the buyer, and take a picture of the information code again." is output.

[0050] In step S117, the seller-side transaction function of the seller-side terminal 10 increases the terminal balance data of the seller-side terminal 10 based on the transaction information decrypted in step S114. Specifically, the seller-side transaction function confirms that payment has been completed on the buyer-side terminal 20 based on the payment completion information contained in the payment completion information code 42, and increases the electronic money terminal balance data of the seller-side terminal 10 by the amount of the transaction.

[0051] In step S118, the seller-side transaction function of the seller-side terminal 10 encrypts the transaction information for this monetary transaction with the seller's private key KS10. In the following step S119, the seller-side transaction function generates a receipt information code 43, which includes the transaction information encrypted in step S118, the seller's public key KP10 stored in the storage unit 15, and information indicating that it is a receipt, and displays it on the display 13.

[0052] In step S120, the buyer-side transaction function of the buyer-side terminal 20 uses the camera 21 to read the receipt information code 43 displayed on the seller-side terminal 10's display 13, and stores it in the storage unit 25. As a result, the buyer-side terminal 20 stores in the storage unit 25 evidence that the transaction has been officially completed.

[0053] Furthermore, if the current monetary transaction is canceled in step S112, the process proceeds to step S121. In step S121, the seller-side transaction function of the seller-side terminal 10 generates and displays a cancellation information code 44 for canceling the current monetary transaction. The cancellation information code 44 can be configured to include information indicating that the current monetary transaction is to be canceled, and can also be configured to include transaction information related to the current monetary transaction (for example, seller-side terminal PID, buyer-side terminal PID, product name, transaction amount, quantity, transaction subject, transaction date and time), as shown in Figure 5.

[0054] In step S122, the buyer-side transaction function of the buyer-side terminal 20 reads the cancellation information code 44. The buyer-side transaction function can read the cancellation information code 44 by capturing an image of the cancellation information code 44 displayed on the display 13 of the seller-side terminal 10 in step S121 with the camera 11. Then, in step S123, the buyer-side transaction function of the buyer-side terminal 20 cancels the reduction in the terminal balance data. Specifically, the buyer-side transaction function retrieves the information indicating the cancellation of the current monetary transaction contained in the cancellation information code 44 read in step S122, and then performs a process to restore the terminal balance data that was reduced in step S109. Furthermore, if the cancellation information code 44 includes not only information indicating the cancellation of the current monetary transaction, but also transaction information such as the seller's terminal PID, buyer's terminal PID, product name, transaction amount, quantity, transaction title, and transaction date and time for the current monetary transaction, the buyer's transaction function can be configured to take this transaction information into consideration to identify the current transaction record and restore the monetary data that was reduced in that transaction.

[0055] As described above, the offline money transaction processing shown in Figures 10 and 11 is performed. At the end of the offline money transaction processing, the terminal balance data of the seller terminal 10 and the server balance data of the seller terminal 10 stored in the server 30 will not match. Therefore, the data update function of the seller terminal 10 accesses the server 30 and updates the server balance data stored in the server 30 to match the terminal balance data stored in the seller terminal 10 when network communication becomes available after the offline money transaction processing. Similarly, at the end of the offline money transaction processing, the terminal balance data of the buyer terminal 20 and the server balance data of the buyer terminal 20 stored in the server 30 will not match. Therefore, the data update function of the buyer terminal 20 accesses the server 30 and updates the server balance data stored in the server 30 to match the terminal balance data stored in the buyer terminal 20 when network communication becomes available after the offline money transaction processing.

[0056] For example, in an environment where online communication is possible, the buyer terminal 20 can send its terminal balance data to the server 30 along with transaction information obtained from the seller terminal 10. Furthermore, if the buyer terminal 20 conducts monetary transactions with multiple seller terminals 10, it can send multiple transaction information obtained from each of these multiple seller terminals 10 to the server 30. In this case, the server 30 can update the buyer terminal 20's server balance data by subtracting the transaction amount included in the transaction information from the server balance data of the buyer terminal 20 stored in the server 30 before the update, based on the transaction information (or multiple transaction information) history obtained from the buyer terminal 20. The server 30 can also be configured to determine whether the updated server balance data of the buyer terminal 20 matches the terminal balance data of the buyer terminal 20 sent from the buyer terminal 20, and output an error to the buyer terminal 20 if they do not match.

[0057] Similarly, in an environment where online communication is possible, the seller terminal 10 can transmit its terminal balance data to the server 30 along with transaction information obtained from the buyer terminal 20. Furthermore, if the seller terminal 10 conducts monetary transactions with multiple buyer terminals 20, it can transmit multiple transaction information obtained from each of these multiple buyer terminals 20 to the server 30. In this case, the server 30 can update the seller terminal 10's server balance data by increasing the amount of the transaction amount included in the transaction information, based on the transaction information (or multiple transaction information) history obtained from the seller terminal 10. The server 30 can also be configured to determine whether the updated seller terminal 10's server balance data matches the terminal balance data of the seller terminal 10 transmitted from the seller terminal 10, and output an error to the seller terminal 10 if there is a mismatch.

[0058] Furthermore, in the embodiments described above, a configuration was illustrated in which the buyer terminal 20 transmits transaction information to the server 30 to update the server balance data of the buyer terminal 20, and the seller terminal 10 transmits transaction information to the server 30 to update the server balance data of the seller terminal 10. However, the configuration is not limited to this, and for example, it is also possible to configure the system so that either the seller terminal 10 or the buyer terminal 20 transmits transaction information to the server 30, thereby updating the server balance data of both the seller terminal 10 and the buyer terminal 20. For example, if the seller terminal 10 transmits transaction information to the server 30, the server 30 can update the server balance data of the seller terminal 10, and also update the server balance data of the buyer terminal 20 that has conducted a monetary transaction with the seller terminal 10.

[0059] In the examples shown in Figures 10 and 11, an offline cash transaction is initiated when the seller inputs transaction information, including the transaction amount, into the seller's terminal 10. However, the system is not limited to this configuration. For example, an offline cash transaction can be initiated when the buyer inputs transaction information, including the transaction amount, into the buyer's terminal 20. For instance, a QR code containing the seller's identification information can be placed in the store, and the buyer can scan the QR code using the buyer's terminal 20, input the product, quantity, transaction amount, transaction title, etc., and approve the payment, thereby completing step S108 of the offline cash transaction process described above.

[0060] Next, the data tampering prevention effect of the money transaction system 1 according to this embodiment will be explained. In the offline money transaction processing shown in Figures 10 and 11, for example, if a purchaser attempts to fraudulently alter the transaction amount of the transaction information contained in the transaction start information code 41 stored in the storage unit 25 of the purchaser terminal 20 to zero or an amount less than the original transaction amount before approving the payment on the purchaser terminal 20, in this embodiment, since the transaction information contained in the transaction start information code 41 stored in the storage unit 25 of the purchaser terminal 20 is stored in an encrypted state with the seller's private key KS10, the transaction amount of the encrypted transaction information cannot be tampered with, and fraudulent data tampering by the purchaser can be prevented. Similarly, if a seller attempts to fraudulently increase the terminal balance data of the seller's terminal 10 by altering the transaction amount to a higher amount than the actual transaction amount, in this embodiment, the transaction information contained in the payment completion information code 42 stored in the storage unit 15 of the seller's terminal 10 is stored encrypted with the buyer's private key KS20. Therefore, it is not possible to alter the transaction amount of the encrypted transaction information, thus preventing such fraudulent data alteration by the seller.

[0061] As described above, in this embodiment, the first or second information terminal is configured to store transaction information encrypted with the private key of the other information terminal, thereby effectively preventing tampering with the encrypted transaction information stored in the first or second information terminal. Furthermore, the first or second information terminal can easily use the encrypted transaction information stored in the first or second information terminal by obtaining the public key from the other information terminal. In addition, the money transaction program in the first or second information terminal can be made obfuscated or encrypted to prevent the program itself from being tampered with, and the security of the program itself is enhanced by performing tamper checks to detect tampering if the program has been altered.

[0062] Although preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the embodiments described above. Various modifications and improvements can be made to the above embodiments, and such modified or improved forms are also included in the technical scope of the present invention.

[0063] For example, in the embodiment described above, from the standpoint of protecting privacy, the seller terminal 10 and the buyer terminal 20 can be configured not to exchange data that could identify the seller terminal 10 and the buyer terminal 20. For example, the seller terminal 10 and the buyer terminal 20 can display an information code 40 that includes only transaction code and transaction amount data as transaction information, thereby configuring the system so that it cannot track information such as who the transaction was with and what the transaction was, similar to a monetary transaction using only actual currency.

[0064] Furthermore, in the embodiments described above, electronic money was used as an example of the monetary data used by the seller's terminal 10 and the buyer's terminal 20. However, the configuration is not limited to this, and for example, it is also possible to use digital currency, points, virtual currency, etc., as monetary data.

[0065] In addition, in the embodiment described above, as shown in Figure 4, the teacher code area 403 is shown to be positioned to the lower left of the information code area 401 as an example of the information code 40. However, the position of the teacher code area 403 is not particularly limited, and it can be positioned, for example, to the upper or lower right of the information code area 401. Also, in the example shown in Figure 4, the teacher code area 403 is shown to be positioned in contact with the information code area 401, but it can also be positioned at a location away from the information code area 401. Furthermore, in the example shown in Figure 4, the information code 40 is shown to have only one teacher code area 403, but it is not limited to this configuration, and it can have multiple teacher code areas 403, such as one teacher code area 403 positioned to the upper and one to the lower of the information code area 401. In addition, in the information code 40, one or more teacher code areas 403 may be placed inside the information code area 401. [Explanation of Symbols]

[0066] 1…Money transaction system 10…Seller's terminal 11…Camera 12… Communications Department 13…Display 14...Input section 15...Storage section 16...Arithmetic section 20... Buyer's device 21... Camera 22... Communications Department 23…Display 24...Input section 25...Storage section 26...Arithmetic section 30... Server 40... Information Code 41...Transaction start information code 42…Payment completion information code 43…Receipt information code 44... Cancellation information code 401... Information code area 402…Information cell 403...Teacher Code Area 404...Teacher cell 405...Cutout symbol 2…Internet connection

Claims

1. A monetary transaction system comprising a first information terminal having a first image display unit and a first image reading unit, and a second information terminal having a second image display unit and a second image reading unit, which performs monetary transactions based on monetary data between the first information terminal and the second information terminal offline, The first information terminal is, A first storage means that stores the first balance data held by the first information terminal and the private key and public key of the first information terminal, A first acquisition means for acquiring data on the transaction amount in the aforementioned monetary transaction, An encryption means for encrypting transaction information, including transaction amount data obtained by the first acquisition means, using the private key of the first information terminal, A monetary processing means that increases or decreases the first balance data based on the transaction amount data obtained by the first acquisition means, The system includes a first display means that displays image information including the encrypted transaction information and the public key of the first information terminal on the first image display unit, The aforementioned second information terminal is, A second storage means for storing the second balance data held by the second information terminal, The second image reading unit is provided with a second image reading means that causes the first information terminal to read the image information, A second acquisition means for obtaining the encrypted transaction information and the public key of the first information terminal from the image information, A decryption means for decrypting the encrypted transaction information using the public key of the first information terminal, A monetary transaction system comprising: a monetary processing means for increasing or decreasing the second balance data based on the transaction amount data contained in the transaction information decrypted by the decryption means.

2. The money transaction system according to claim 1, wherein the second information terminal stores the transaction information in an encrypted state.

3. The second information terminal stores the private key and public key of the second information terminal in the second storage means. The aforementioned second information terminal is, A second encryption means that encrypts the transaction information obtained from the first information terminal using the secret key of the second information terminal, The money transaction system according to claim 1, further comprising: a second display means for displaying image information including transaction information encrypted by the second encryption means and the public key of the second information terminal on the second image display unit.

4. In a monetary transaction system that performs monetary transactions based on monetary data between a first information terminal and a second information terminal offline, the first information terminal is: A first storage means that stores the first balance data held by the first information terminal and the private key and public key of the first information terminal, A first acquisition means for acquiring data on the transaction amount in the aforementioned monetary transaction, An encryption means for encrypting transaction information, including transaction amount data obtained by the first acquisition means, using the private key of the first information terminal, A monetary processing means that increases or decreases the first balance data based on the transaction amount data obtained by the first acquisition means, An information terminal having a first display means for displaying image information including the encrypted transaction information and the public key of the first information terminal.

5. In a money transaction system that performs money transactions offline based on money data between a first information terminal and a second information terminal, the second information terminal is: The first information terminal has means for displaying image information including transaction information, which includes transaction amount data encrypted with the private key of the first information terminal, and the public key of the first information terminal for decrypting the encrypted transaction information. The aforementioned second information terminal is, A second storage means for storing the second balance data held by the second information terminal, A second image reading means for reading the image information displayed by the first information terminal, A second acquisition means for obtaining the encrypted transaction information and the public key of the first information terminal from the image information, A decryption means for decrypting the encrypted transaction information using the public key of the first information terminal, An information terminal having a money processing means for increasing or decreasing the second balance data based on the transaction amount data contained in the transaction information decrypted by the decryption means.

6. The information terminal according to claim 5, which stores the transaction information in an encrypted state.

7. An information terminal according to claim 4, and a server capable of communicating with the information terminal according to claim 5 or claim 6, A server storage unit that stores the first balance data and / or the second balance data as server balance data, A server having: an update unit that acquires the first balance data and / or the second balance data as terminal balance data from the first information terminal and / or the second information terminal, acquires the transaction information, and updates the server balance data stored in the server storage unit based on the acquired terminal balance data and the transaction information.

8. A money transaction system comprising a first information terminal having a first image display unit and a first image reading unit, and a second information terminal having a second image display unit and a second image reading unit, which performs offline money transactions based on money data between the first information terminal and the second information terminal, wherein a computer program executed by the first information terminal, A function for storing the first balance data held by the first information terminal, and the private key and public key of the first information terminal, A function to acquire data on the transaction amount in the aforementioned monetary transaction, A function to encrypt transaction information, including the acquired transaction amount data, using the private key of the first information terminal, A function to increase or decrease the aforementioned first balance data based on the acquired transaction amount data, A computer program having a function to display image information including the encrypted transaction information and the public key of the first information terminal.

9. A money transaction system comprising a first information terminal having a first image display unit and a first image reading unit, and a second information terminal having a second image display unit and a second image reading unit, wherein money transactions based on money data between the first information terminal and the second information terminal are performed offline, the computer program executed by the second information terminal, The first information terminal has means for displaying image information including transaction information, which includes transaction amount data encrypted with the private key of the first information terminal, and the public key of the first information terminal. The computer program of the second information terminal is: The second information terminal has a function to store the second balance data it possesses, The second image reading unit has a function to read the image information displayed by the first information terminal, A function to obtain the encrypted transaction information and the public key of the first information terminal from the aforementioned image information, A function to decrypt the encrypted transaction information using the public key of the first information terminal, A computer program having a function to increase or decrease the second balance data based on the transaction amount data contained in the decoded transaction information.

10. The computer program according to claim 9, further comprising a function for storing the aforementioned transaction information in an encrypted state.

11. A monetary transaction method performed on the first information terminal when executing an offline monetary transaction based on monetary data between the first information terminal and the second information terminal, using a first information terminal having a first image display unit and a first image reading unit, and a second information terminal having a second image display unit and a second image reading unit, The first information terminal stores the first balance data it possesses, and the first information terminal's private key and public key. Obtain data on the transaction amount in the aforementioned monetary transaction, The transaction information, including the acquired transaction amount data, is encrypted using the private key of the first information terminal. Based on the acquired transaction amount data, the aforementioned first balance data is increased or decreased. A computer program having a function to display image information including the encrypted transaction information and the public key of the first information terminal.

12. A monetary transaction method performed on the second information terminal when executing a monetary transaction based on monetary data between the first information terminal and the second information terminal offline, using a first information terminal having a first image display unit and a first image reading unit, and a second information terminal having a second image display unit and a second image reading unit, The first information terminal has means for displaying image information including transaction information, which includes transaction amount data encrypted with the private key of the first information terminal, and the public key of the first information terminal. The aforementioned second information terminal is, The second information terminal stores the second balance data it possesses. The second image reading unit reads the image information displayed by the first information terminal, From the aforementioned image information, the encrypted transaction information and the public key of the first information terminal are obtained. Using the public key of the first information terminal, the encrypted transaction information is decrypted. A monetary transaction method that increases or decreases the second balance data based on the transaction amount data contained in the decrypted transaction information.

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