JP6488613B2 - Trading system and program - Google Patents

Description

  The present invention relates to a technique for preventing illegal transactions.

  2. Description of the Related Art Conventionally, there is a technique for preventing illegal transactions in electronic transactions. For example, in Patent Document 1, after a temporary reception ID is displayed on a first user terminal such as a personal computer, a temporary reception ID is transmitted by a second user terminal such as a mobile phone, thereby authenticating the user at the time of login. A technique for strengthening is disclosed. Non-Patent Documents 1 and 2 disclose security threats when performing online banking. For example, in Non-Patent Document 1, in online banking via the Internet, malware (virus) that has secretly entered a user terminal such as a personal computer or smartphone monitors the communication status, and the user performs online banking. When it is detected that the browser has started, a “Man-in-the-Browser attack” that steals and alters the communication content of the browser is disclosed.

JP-A-2005-202806

Bank of Japan Financial Research Institute homepage, Discussion Paper No. 2013-J-4, Measures against Man-in-the-Browser Attack against Online Banking Safety Evaluation of “Transaction Authentication”, Masataka Suzuki, Junji Nakayama, Kunikuni Furuhara, [Search on August 26, 2013] Internet <URL: http://www.imes.boj.or.jp/research/abstracts/japanese/13-J-04.html> FFRI website, security report Monthly Research July 2012, new attacks on browsers and new countermeasures, Tsukasa Oi, [searched on August 26, 2013], Internet <URL: http: //www.fourteenforty .jp / research / monthly_research.htm> CRYPTREC home page, 2008 list guide (message authentication code), National Institute of Information and Communications Technology, Information Processing Promotion Organization, [Search August 26, 2013], Internet <URL: http: // www .cryptrec.go.jp / report / c08_listguide2008_mac_v7.pdf>

  When a user terminal used for online banking is infected with a virus and is subjected to a Man-in-the-Browser attack, the web browser is hijacked, so that authentication of the user at login to online banking is strengthened. There is a problem that the countermeasures cannot prevent fraudulent transactions. Then, this invention makes it a main subject to provide the transaction system and program which can detect an unauthorized transaction suitably.

One aspect of the present invention is a transaction system including a server that executes a process related to a transaction and a terminal that instructs the server to execute the process related to the transaction. The terminal inputs the content of the transaction. Display control means for displaying a transaction screen , first transmission control means for transmitting input information indicating the transaction content input on the transaction screen to the server, and the transaction screen after the transaction content is input . Second transmission control means for transmitting image data to the server, and the server includes transaction details indicated by the input information received from the first transmission control means, and the received from the second transmission control means. If the transaction content extracted from the image data is different, an unauthorized transaction detection means for stopping execution of the process related to the transaction is provided.

The transaction system includes a server that executes a process related to a transaction and a terminal that instructs the server to execute the process related to the transaction. At the terminal, a transaction screen for inputting transaction details is displayed, and input information indicating transaction details input on the transaction screen is transmitted to the server by the first transmission control means. Moreover, the image data of the transaction screen after the transaction content is input is transmitted to the server by the second transmission control means. When the transaction content indicated by the input information received from the first transmission control unit is different from the transaction content extracted from the image data received from the second transmission control unit, the server stops execution of the process related to the transaction. .

  According to the above transaction system, even if the terminal is infected with a virus, the server accurately determines whether or not the transaction content has been tampered with based on the input information on the transaction screen transmitted by the terminal, and the online transaction. By detecting that is under a Man-in-the-Browser attack, unauthorized transactions can be prevented.

  In a preferred example, the terminal includes a storage unit that stores a first program for display and a second program different from the first program, and the display control unit and the first program are executed by the first program. Transmission control means is configured, and the second transmission control means is configured by the second program. In another preferred example, the terminal includes a storage unit that stores a third program, and the display control unit, the first transmission control unit, and the second transmission control unit are operated by the third program. Composed.

In one aspect of the transaction system, the second transmission control unit transmits image data capturing the transaction screen after transaction details are input to the server, and the fraudulent transaction detection unit includes the second transaction detection unit. The transaction content is recognized by performing a character recognition process on the image data received from the transmission control means. In this aspect, even if the terminal is infected with a virus, information indicating the correct transaction content can be transmitted to the server by image data.

  In another aspect of the transaction system, the second transmission control unit transmits the image data in which the character data input to the transaction screen is embedded to the server as information based on the input. The fraudulent transaction detection unit recognizes the transaction content based on the character data extracted from the image data received from the second transmission control unit. In this aspect, even when the terminal is infected with a virus, information indicating the correct transaction content can be transmitted to the server by the character data embedded in the image data.

In another aspect of the transaction system, the storage unit of the terminal stores an encryption key for performing encryption and / or attaching a message authentication code, and the server is encrypted with the encryption key . a storage unit that stores a decryption key for carrying out the decoding and / or verification of the message authentication code data, the second transmission control means, encryption and / or the said image data by the encryption key sending with the message authentication code to the image data, the trafficking detecting means, decoding and / or the message authenticator attached to the image data of the image data received from the second transmission control means by said decryption key Perform code verification. Note that the above encryption key and decryption key may be the same or different. According to this aspect, the terminal can safely transmit the information transmitted by the second transmission control means to the server.

  In another aspect of the transaction system, the storage unit of the terminal stores an encryption key that is different from an encryption key stored in another terminal that instructs the server to execute processing related to the transaction, and the storage unit of the server A different decryption key is stored for each terminal. According to this aspect, even when an encryption key stored in a certain terminal is stolen, it is possible to suitably suppress the influence on the safety of transactions by other terminals.

In another aspect of the transaction system, the second transmission control unit transmits information related to the previous transaction in addition to the image data , and the fraudulent transaction detection unit receives the information received from the second transmission control unit. based on the information on transactions of the image data preceding, it is determined whether a fraudulent transaction. According to this aspect, even if the information based on the inputs transmitted by the first and second transmission control means is both altered, the server can preferably detect the illegal transaction.

In another aspect of the transaction system, the second transmission control unit transmits a predetermined character string in addition to the image data , and the illegal transaction detection unit receives the image received from the second transmission control unit. based on the data and the predetermined character string, it is determined whether a fraudulent transaction. According to this aspect, even when information based on the inputs transmitted by the first and second transmission control means is both altered, the server can detect an illegal transaction.

In another aspect of the present invention, a program executed by a terminal having a computer includes display control means for displaying a transaction screen for inputting transaction details, and input information indicating transaction details input on the transaction screen. The computer is caused to function as first transmission control means for transmitting to a server that executes processing relating to transactions, and second transmission control means for transmitting image data of the transaction screen after transaction details are input to the server.

In still another aspect of the present invention, the computer has a computer and displays a transaction screen for inputting transaction details, and executes processing related to the transaction with input information indicating the transaction details input on the transaction screen. The program executed by the terminal that transmits to the server causes the computer to function as a transmission control unit that transmits image data of the transaction screen after the transaction content is input to the server.

  The terminal according to the present invention can be configured by installing the above-described program in a computer and causing it to function.

  In still another aspect of the present invention, a program causes a computer to function as any one of the servers described above. By installing this program in a computer and causing it to function, the server according to the present invention can be configured.

  According to the transaction system according to the present invention, even if the terminal displaying the transaction screen is infected with a virus or the like, the server may or may not tamper with the transaction contents based on the input information on the transaction screen transmitted by the terminal. Can be accurately determined, and illegal transactions can be suitably prevented.

The structure of the transaction system which concerns on embodiment is shown. The block diagram of a service provider server is shown. The block diagram of a user terminal is shown. It is a flowchart which shows the process sequence in 1st Embodiment. It is a flowchart which shows the flow of a process when there exists an attack which falsifies the input information of a transaction screen. A display example of the login screen is shown. The example of a display of a transaction screen is shown. An example of captured image data is shown. A display example of the transaction content confirmation screen is shown. It is a display example of a transfer completion screen. It is a flowchart which shows the process sequence in 2nd Embodiment. It is a flowchart which shows the process sequence in 3rd Embodiment. The example of the additional image by the modification of 3rd Embodiment is shown. The structure of the transaction system which concerns on a modification is shown.

  Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. The transaction system described below is a system that can suitably prevent tampering of transaction contents when performing electronic transactions such as online banking using the Internet.

[First Embodiment]
(Structure of transaction system)
FIG. 1 shows a configuration of a transaction system according to the present embodiment. The transaction system includes a service provider server 1 managed by a service provider such as a bank, and a user terminal 3 used by a user who receives the above service. The service provider server 1 and the user terminal 3 perform data communication via a communication network 2 such as the Internet. In the example of FIG. 1, an attacker server 4 that attempts to execute unauthorized transactions by altering the communication content between the service provider server 1 and the user terminal 3 is connected to the communication network 2.

  When the user terminal 3 is infected with malware (virus) that can be controlled by the attacker server 4, the attacker server 4 controls the user terminal 3 via the malware, and the user of the user terminal 3 The content displayed by the Web browser or the input content is stolen, or the data the malware steals from the user terminal 3 and transmits to the attacker server 4 is received. For example, the malware infected with the user terminal 3 falsifies the input content on the screen (also referred to as “transaction screen”) for specifying the transaction content displayed by the user terminal 3 by the Web browser, and the service provider server 1. The response content from the service provider server 1 is also rewritten so that it has not been tampered with. Thereby, the attacker tries to tamper with the transaction contents so that the user of the user terminal 3 does not notice. As described above, the malware infected with the user terminal 3 executes a so-called Man-in-the-Browser attack. As will be described later, the transaction system according to the present embodiment prevents unauthorized transactions caused by malware infected by such user terminals 3 altering transaction contents.

  FIG. 2 is a block diagram of the service provider server 1. The service provider server 1 includes a display unit 11 such as a display, an input unit 12 such as a keyboard, a storage unit 13, a communication unit 14 that performs data communication, and a control unit 15. Each of these elements is connected to each other via a bus line 10.

  The storage unit 13 is configured by a hard disk or a memory such as a ROM or a RAM. The storage unit 13 stores information necessary for user authentication such as a login ID and a password and other user information in a database. The storage unit 13 also stores information necessary for generating display information for each screen such as a program necessary for the service provider server 1 to function as a Web server and a transaction screen displayed by the user terminal 3. Remember. The storage unit 13 stores a secret key (decryption key) for decrypting data encrypted by the user terminal 3 with a predetermined public key.

  The control unit 15 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown), and performs various controls on each component in the service provider server 1. And the control part 15 functions as a "illegal transaction detection means" in this invention.

  FIG. 3 is a block diagram of the user terminal 3. The user terminal 3 includes a display unit 31 such as a display, an input unit 32 such as a keyboard, a storage unit 33, a communication unit 34 that performs data communication, and a control unit 35. These elements are connected to each other via a bus line 30.

  The storage unit 33 is configured by a hard disk or a memory such as a ROM or a RAM. The storage unit 33 stores each program executed by the control unit 15. For example, the storage unit 33 stores a program for starting a Web browser (viewer) that displays a predetermined Web page based on an HTML file or the like received from the service provider server 1. The above-described program is an example of the “first program” in the present invention.

  Further, the storage unit 33 operates in cooperation with the service provider server 1 and stores a program (also referred to as “agent program”) for determining whether or not the transaction content has been tampered with. The agent program is activated, for example, when the user terminal 3 is activated, when the web browser is activated, or when the user terminal 3 displays a transaction screen using the web browser. The agent program is an example of the “second program” in the present invention. The storage unit 33 stores in advance a public key (encryption key) for encrypting data transmitted from the user terminal 3 to the service provider server 1 based on the agent program, together with the agent program.

  The control unit 35 includes a CPU, a ROM, a RAM, and the like (not shown), and performs various controls on each component in the user terminal 3. The control unit 35 performs predetermined processing by executing each program stored in the storage unit 33. For example, the control unit 35 executes the agent program to generate image data (also referred to as “capture image data Im”) indicating the transaction screen in which the transaction content is input, and the storage unit 33 stores the image data. It is encrypted with the public key and transmitted to the service provider server 1. The control unit 35 functions as “display control means”, “first transmission control means”, and “second transmission control means” in the present invention.

(Processing flow)
Next, processing of the transaction system in the present embodiment will be described. Schematically, the service provider server 1 refers to the captured image data Im transmitted from the user terminal 3 based on the agent program, so that input information indicating the transaction content transmitted based on the function of the Web browser is obtained. Check if it has been tampered with. Thereby, even if it is a case where the web browser of the user terminal 3 is taken over by a virus, an unauthorized transaction is prevented suitably.

(1) Process Overview FIG. 4 is a flowchart showing a process procedure executed by the transaction system in the present embodiment. In FIG. 4 and FIG. 5 described later, the process executed by the user terminal 3 based on the function of the Web browser and the process executed by the user terminal 3 based on the agent program are described separately.

  First, based on the display information received from the service provider server 1, the user terminal 3 displays a login screen with a Web browser and accepts input of login information such as a login ID and password (step S101). A display example of the login screen will be described later with reference to FIG. Then, the user terminal 3 transmits the login information input on the login screen to the service provider server 1.

  Next, the service provider server 1 identifies and authenticates the user based on the login information received from the user terminal 3 (step S102). For example, the service provider server 1 identifies the user of the login information transmission source by the login ID included in the login information, and authenticates the user by the password received together with the login ID. And service provider server 1 complete | finishes the process of a flowchart, when a user cannot be authenticated (step S103; No).

  And the service provider server 1 transmits the display information of a transaction screen to the user terminal 3, when a user can be authenticated (step S103; Yes) (step S104). A display example of the transaction screen will be described later with reference to FIG. Then, the user terminal 3 receives the display information from the service provider server 1, displays the transaction screen by the Web browser, receives an input for specifying the transaction details by the user, and an instruction to execute the transaction (step S105). ).

  Upon receiving the transaction execution instruction, the user terminal 3 generates capture image data Im based on the agent program (step S107) and stores it in the storage unit 33. An example of the captured image data Im will be described later with reference to FIG.

Next, the user terminal 3 encrypts the captured image data Im using the public key stored in the storage unit 33 based on the agent program (step S108). Then, the user terminal 3 transmits the encrypted captured image data Im to the service provider server 1. The service provider server 1 receives the encrypted captured image data Im and decrypts it with a secret key stored in advance in the storage unit 13 (step S109). Thereby, the service provider server 1 acquires the captured image data Im. And the service provider server 1 extracts the information (it is also called "transaction information Ia") which shows the transaction content displayed on the capture image data Im by character recognition (step S110). For example, the service provider server 1 extracts, as the transaction information Ia, a character string representing each item such as a bank name and a branch name, an account number, and a transfer amount input on the transaction screen by character recognition.

  Next, the user terminal 3 transmits input information indicating transaction details input on the transaction screen based on the function of the Web browser (step S111). In this case, the user terminal 3 transmits the above input information by the POST method of HTTP (Hyper Text Transfer Protocol). Note that the communication in step S111 is encrypted by, for example, encrypted communication using SSL (Secure Socket Layer).

  Next, the service provider server 1 receives the transaction screen input information from the user terminal 3, and extracts information indicating transaction details (also referred to as "transaction information Ib") from the input information (step S112). Here, the service provider server 1 extracts, as the transaction information Ib, a character string representing each item such as a bank name, a branch name, an account number, and a transfer amount, like the transaction information Ia.

  And the service provider server 1 determines whether the transaction information Ia and the transaction information Ib show the same content (step S113). As a result, the service provider server 1 determines whether or not the input information on the transaction screen transmitted by the HTTP POST method has been tampered with. If the transaction information Ia and the transaction information Ib indicate the same content (step S113; Yes), the service provider server 1 determines that the input information on the transaction screen received in step S112 has not been tampered with, and the transaction The display information of the content confirmation screen is transmitted to the user terminal 3 (step S114). On the other hand, when the transaction information Ia and the transaction information Ib indicate different contents (step S113; No), the service provider server 1 may have altered the transaction screen input information received in step S112. Judgment is made and the process of the flowchart is terminated without completing the transaction. Thereby, the service provider server 1 can prevent an unauthorized transaction.

  Then, after the service provider server 1 transmits information on the transaction content confirmation screen to the user terminal 3, the user terminal 3 displays a transaction content confirmation screen based on the received display information (step S115). Thereafter, the user terminal 3 detects a transaction execution confirmation based on the user operation, and transmits information indicating the transaction execution confirmation to the service provider server 1 (step S116). And user terminal 3 receives the above-mentioned directions information, and performs the transaction which transaction information Ib received at Step S112 shows (Step S117).

(Modification)
The information on the transaction content confirmation screen provided by the service provider server 1 may be processed as hidden if necessary. That is, after step S113; Yes, the process may proceed to step S117. By performing such processing, it is possible to provide the user with transfer processing in online banking that is not different from the conventional one. Further, since it is possible to conceal that the transaction content has been tampered with from the attacker, it is possible to suitably prevent further unauthorized transactions. However, if the process proceeds to step S113; No in this modification, a message indicating that the transaction has failed is displayed to the user.

(2) Case of Tampering FIG. 5 shows the flow of processing when the input information on the transaction screen transmitted based on the function of the Web browser is tampered, that is, when there is a Man-in-the-Browser attack. It is a flowchart to show. In the example shown in FIG. 5, the user terminal 3 is infected with a virus controlled by the attacker server 4, and the contents displayed on the Web browser and the input to the transaction screen displayed on the Web browser can be stolen and altered. It shall be in In FIG. 5, for the sake of convenience, part of the display of the steps in which the same processing as that in the flowchart shown in FIG. 4 is performed is omitted.

  First, in step S107, the user terminal 3 generates captured image data Im, and in step S108, the captured image data Im is encrypted with a public key and transmitted. In this case, since the user terminal 3 executes steps S107 and S108 by an agent program different from the Web browser program, the user terminal 3 generates and transmits the captured image data Im without being affected by the virus infection. . Thereby, the service provider server 1 acquires the transaction information Ia at step S110.

  Thereafter, in step S111, the user terminal 3 transmits the input information of the transaction screen based on the function of the Web browser. In this case, in step S201, the attacker server 4 controls the virus infected by the user terminal 3, thereby falsifying the input information on the transaction screen, and transmits the falsified input information to the service provider server 1. To do. Even in the case where the user terminal 3 performs encrypted communication using SSL or the like in step S111, the attacker server 4 falsifies the input information before encryption and then encrypts the input information before encryption. Transmit to terminal 3. Therefore, in this case, the input information on the transaction screen transmitted by the function of the Web browser is falsified regardless of whether or not encrypted communication is performed.

  Then, in step S112, the service provider server 1 extracts the transaction information Ib from the received input information. In this case, since the input information has been falsified by the attacker server 4 in step S201, the transaction information Ib indicates the illegal transaction content rewritten by the attacker server 4.

  Next, in step S113, the service provider server 1 determines whether or not the contents of the transaction information Ia and the transaction information Ib match, and determines that the transaction information Ia and the transaction information Ib are not the same contents. Therefore, in this case, the service provider server 1 ends the process of the flowchart without completing the transaction.

  As described above, even when the user terminal 3 is infected with a virus and the communication data transmitted based on the function of the Web browser is falsified, the service provider server 1 uses the agent program to the user terminal 3. The tampering can be detected based on the captured image data Im transmitted by, and the illegal transaction can be surely prevented.

(Display screen example)
Next, display screen examples of the user terminal 3 relating to the processing of the flowcharts of FIGS. 4 and 5 will be described with reference to FIGS. 6 to 10 show an example in which the transfer is performed by online banking.

  FIG. 6 shows a display example of a login screen displayed by the user terminal 3 using a Web browser in step S101. As shown in FIG. 6, the user terminal 3 displays a login ID input field 50 for inputting a login ID, a password input field 51 for inputting a password, and a login button 52 on the login screen. doing. When the user terminal 3 detects that the login button 53 has been selected by a mouse click operation or the like, the user terminal 3 uses the login ID input in the login ID input field 50 and the password input in the password input field 51. The login information including it is transmitted to the service provider server 1.

  FIG. 7 shows a display example of the transaction screen displayed by the user terminal 3 using the web browser in step S105. On the transaction screen shown in FIG. 7, the user terminal 3 includes transfer destination designation fields 54 to 56 for designating the bank name, branch name, and account number of the transfer destination, and the transfer amount for designating the transfer amount. A designation field 57 and a transfer execution button 58 are displayed.

  On the transaction screen of FIG. 7, the user of the user terminal 3 presses the transfer execution button 58 after inputting information on the transfer destination and the transfer amount in the respective designation fields 54 to 57 on the transaction screen. At this time, the agent program captures the screen of FIG. 7 (processing to capture the screen displayed on the display etc. and save it as image data), generates the captured image data Im, encrypts it with the public key, and provides the service To server 1. FIG. 8 shows an example of the captured image data Im. The captured image data Im is an image obtained by capturing the transaction screen shown in FIG. 7, and is the same as the transaction screen shown in FIG.

  When the transfer execution button 58 is selected by the user, the user terminal 3 provides the information input in the transfer destination designation fields 54 to 56 and the transfer amount designation field 57 in step S111 using the HTTP POST method. To server 1.

  FIG. 9 shows a display example of the transaction content confirmation screen displayed by the user terminal 3 in step S115. As shown in FIG. 9, the user terminal 3 displays the transfer destination and the transfer amount, which are the transaction details, on the transaction content confirmation screen, and the confirmation button 61 for final confirmation of the transaction execution and the transaction execution. A cancel button 62 for canceling is displayed. If the user terminal 3 detects that the confirmation button 61 has been selected, in step S116, the user terminal 3 transmits information instructing transaction execution to the service provider server 1, and the service provider server 1 executes the transaction. I do. Thereafter, the user terminal 3 receives display information related to transaction completion from the service provider server 1 and displays a screen indicating that the transaction is completed by a Web browser. FIG. 10 is a display example of a transfer completion screen. In the example of FIG. 10, the user terminal 3 displays the reception number assigned by the service provider server 1 for the executed transfer transaction.

  Here, a supplementary description will be given of a case where a Man-in-the-Browser attack has occurred. The attacker server 4 controls the virus infected by the user terminal 3, thereby transmitting to the service provider server 1 information obtained by illegally rewriting the transfer destination and transfer amount on the transaction screen shown in FIG. 7. Furthermore, since the attacker server 4 disguises that the transaction has been normally performed, the attacker server 4 generates a transaction content confirmation screen indicating the transfer destination and the transfer amount before tampering, and displays the screen on the Web browser of the user terminal 3. Even in this case, the service provider server 1 can accurately determine the presence / absence of tampering by referring to the captured image data Im, and can prevent unauthorized transactions. In this way, the service provider server 1 can prevent unauthorized transactions by detecting that online transactions are subject to a Man-in-the-Browser attack.

[Second Embodiment]
In the first embodiment described above, the user terminal 3 executes processing related to transactions using a Web browser and an agent program. On the other hand, in the second embodiment, processing related to transactions is executed by one program (hereinafter referred to as “integrated program” for convenience). An example of the integrated program is a program in which a Web browser function is incorporated into a program for electronic transactions such as online banking. The integrated program has a transaction content input / display function and a screen information acquisition / transmission function. The integrated program is an example of the “third program” in the present invention.

  FIG. 11 is a flowchart illustrating a processing procedure according to the second embodiment. As understood from comparison with FIG. 4, in the second embodiment, the transaction content input / display function of the integrated program executes the same processing as the Web browser in the first embodiment, and the screen information acquisition / transmission function is the first embodiment. The same processing as the agent program in the embodiment is executed. That is, in the second embodiment, the process executed by the user terminal 3 is the same as that in the first embodiment. The processing executed by the service provider server 2 in the second embodiment is the same as that in the first embodiment. Thereby, also in 2nd Embodiment, the alteration of the input information by an attacker server can be detected similarly to 1st Embodiment, and an unauthorized transaction can be prevented.

[Third Embodiment]
In said 1st and 2nd embodiment, the user terminal 3 transmits the capture image of a transaction screen to the service provider server 1, and the service provider server 1 is information (transaction) which shows transaction content by character recognition from a capture image. Information Ia) is extracted. Instead, in the third embodiment, the user terminal 3 embeds text (character data) input to the transaction screen in the captured image data of the transaction screen and transmits it to the service provider server 1. The service provider server 1 extracts character data embedded in the captured image data, and uses it as transaction information Ia indicating transaction details. Except for this point, the third embodiment is basically the same as the first and second embodiments.

  FIG. 12 is a flowchart illustrating a processing procedure according to the third embodiment. FIG. 12 shows a case where the integrated program operates on the user terminal 3 as in the second embodiment.

  As understood from comparison with FIG. 11, in the third embodiment, steps S105x and S107x are added, and step S110 is replaced with step S110x. Except for this, the processing of the third embodiment shown in FIG. 12 is the same as the processing of the second embodiment shown in FIG.

  Specifically, in step S105, when the transaction content input / display function of the user terminal 3 receives the user's input and the transaction execution input on the transaction screen (step S105), the image information acquisition / transmission function receives the input text. Is acquired (step S105x). Next, the image information acquisition / transmission function generates capture image data Im (step S107), and further embeds the text acquired in step S105x in the capture image data Im (step S107x). Then, the image information acquisition / transmission function encrypts the captured image data Im with the public key and transmits it to the service provider server 1 (step S108).

  The service provider server 1 receives the encrypted captured image data Im and decrypts it with the secret key (step S109). Next, the service provider server 1 extracts the text embedded in the captured image (step S110x), and performs the subsequent processing using this as transaction information Ia. That is, the service provider server 1 uses this text as transaction information Ia, and performs a match determination with the transaction information Ib in step S113. Since the processing after step S112 is the same as in the first and second embodiments, the description thereof is omitted.

  As described above, in the third embodiment, the text input to the transaction screen is embedded in the captured image data and transmitted, and the service provider server 1 extracts the text from the captured image data and determines whether the contents match. Therefore, unlike the first and second embodiments, there is no need to perform character recognition on the captured image data on the service provider server 1 side.

  FIG. 12 shows an example in which the third embodiment is applied to the case where an integrated program is used as in the second embodiment. However, the third embodiment is similar to the first embodiment in the Web browser and the agent program. It can also be applied when using.

  As a technique for embedding text in captured image data, various known techniques can be applied. For example, techniques such as steganography and digital watermarking can be used. The digital watermark may be perceptible or difficult to perceive. Further, for example, as described in Japanese Patent No. 5359650, a method of embedding text information in a gap between image formats may be applied.

  As a modification, an image corresponding to the text content may be added to the captured image data. For example, the text “25 yen” may be represented by an image using a rectangle and a circle as shown in FIG. 13, and this image may be drawn in the captured image.

[Countermeasures when the captured image data Im is falsified]
Similar to the example shown in FIG. 5, the user terminal 3 is infected with a virus controlled by the attacker server 4, and the content displayed on the Web browser and the input to the transaction screen displayed on the Web browser can be stolen and altered. In such a state, there is a possibility that the captured image data Im is falsified by a virus prepared by the attacker.

  As a countermeasure against this, for example, the transaction system may execute a countermeasure using a message authentication code described in Non-Patent Document 3 described above. This specific example will be described below. First, the storage unit 13 of the service provider server 1 and the storage unit 33 of the user terminal 3 store a common key in advance. Then, in addition to or instead of encrypting the captured image data Im with the public key in step S108, the user terminal 3 performs message authentication using a predetermined algorithm from the above-described key and the captured image data Im. A code is generated, and the generated message authentication code is attached to the captured image data Im and transmitted to the service provider server 1. The service provider server 1 generates a message authentication code from the received captured image data Im and the common key stored in the storage unit 13 using a predetermined algorithm, and receives the message authentication code received from the user terminal 3. It is determined whether or not the same. When the service provider server 1 determines that the message authentication codes are not the same, the service provider server 1 determines that the captured image data Im has been tampered with, and ends the process of the flowchart without executing the transaction. In this way, by using the message authentication code, the transaction system can accurately detect unauthorized transactions even if the captured image data Im has been tampered with by a virus prepared by an attacker, and suitably execute the transaction. Can be prevented.

[Countermeasures when the public key is stolen]
When the public key is stolen, the attacker server 4 creates the captured image data Im indicating the illegal transaction content by the virus, encrypts it with the stolen public key, and transmits it to the service provider server 1. It becomes possible to cause the service provider server 1 to execute unauthorized transactions. Considering the above, a countermeasure when the public key is stolen by the attacker server 4 will be described.

  In the first example, the transaction system uses a public / private key pair that is different for each user. Specifically, the user terminal 3 stores a public key different from the public key stored in the user terminal used by other users, and the service provider server 1 stores the public key stored in each user terminal. Each secret key corresponding to the key is stored. In step S109 in FIG. 4, the service provider server 1 decrypts the encrypted captured image data Im using the secret key corresponding to the user identified in step S102. According to the first example, even if the public key of a certain user terminal is stolen, there is no effect on the transaction of other user terminals. The expansion of damage in the case of failure can be suitably suppressed.

  In the second example, instead of or in addition to the first example, in step S107, the user terminal 3 shows the content of the transaction executed last time in addition to the captured image data Im based on the agent program. Information (also referred to as “previous transaction information”) is encrypted with the public key and transmitted to the service provider server 1. The service provider server 1 decrypts the captured image data Im and the previous transaction information with the secret key, and then determines whether the decrypted previous transaction information is correct. In this case, the service provider server 1 stores the previous transaction information of each user in the storage unit 13, and the decrypted previous transaction information does not match the target previous transaction information stored in the storage unit 13. In the case, the process of the flowchart is terminated without completing the transaction.

  According to the 2nd example, even if it is a case where a public key is stolen by the attacker server 4, the transaction system can suppress appropriately execution of an unauthorized transaction.

  In the second example, the user terminal 3 may encrypt a predetermined character string together with the captured image data Im instead of the previous transaction information. In this case, the predetermined character string may be a unique identification number stored in an external device such as a USB memory distributed from a bank or the like that manages the service provider server 1, and is distributed in advance to the user. It may be a number in the random number table. In this case, the user terminal 3 may read the above-described identification number from an external device connected to the user terminal 3 based on the agent program, or may accept an input of a number in the random number table from the user. Even in this example, when the public key is stolen by the attacker server 4, the transaction system can suitably suppress the execution of the illegal transaction.

  Here, a supplementary description will be given of a case where the agent program has been tampered with. In this case, the user terminal 3 cannot normally execute the processing of step S107 and step S108 based on the agent program, and cannot transmit the encrypted captured image data Im to the service provider server 1. Therefore, in this case, since the service provider server 1 cannot acquire the captured image data Im to be received in step S109, the service provider server 1 interrupts the processing. Therefore, in this case, fraudulent transactions are not executed.

[Example of agent program]
The above agent program can actually be realized as follows. In one method, the agent program is a client-side script (typically JavaScript (registered trademark)), and is included in the HTML source of the online banking web page of the bank. When the user accesses the bank's online banking website using the web browser of the user terminal 3, the agent program is downloaded to the user terminal 3 together with the HTML source of the online banking web page. As described above, this agent program captures the screen of the Web page when the user depresses the “execute transfer” button 58 on the Web page of the user terminal 3 (FIG. 7), and captures the captured image data. Generate.

  In the second method, the agent program is an application program preinstalled in the user terminal 3. This program is started as a resident application in a form that is not displayed on the screen. When the Web browser detects that the transaction screen as shown in FIG. 7 is displayed, the transaction screen is captured to generate captured image data.

[Modification]
Next, a modification of this embodiment will be described. The following modifications may be applied in any combination to the above-described embodiment.

(Modification 1)
The configuration of the transaction system shown in FIG. 1 is an example, and the configuration to which the present invention is applicable is not limited to this. For example, the service provider server 1 may be composed of a plurality of servers.

  FIG. 14 shows a schematic configuration of a transaction system according to a modification. In the example of FIG. 14, the service provider server 1 includes a service provider authentication server 1A that performs user authentication in steps S102 and S103 in FIG. 4, and a service provider transaction server 1B that performs processing related to transactions after user authentication. And two servers. Then, the service provider authentication server 1A and the service provider transaction server 1B perform transmission / reception of data necessary for executing the assigned processing as necessary. In the example of FIG. 14, the user terminal 3 is realized by a smartphone instead of the notebook PC. And even if it is a structural example of FIG. 14, the user terminal 3 transmits capture image data Im to the service provider transaction server 1B based on user operation. Thereby, the service provider transaction server 1B can suitably determine whether or not the transaction content has been tampered with.

(Modification 2)
In the description of FIG. 4, the user terminal 3 and the service provider server 1 exchange the captured image data Im by encrypting with the public key cryptosystem. Instead of this, the user terminal 3 and the service provider server 1 may encrypt the captured image data Im by a common key encryption method and exchange the captured image data Im. In this case, the user terminal 3 and the service provider server 1 each store a common key in advance before executing the flowchart of FIG. Thus, the present invention is preferably applied even when the same (common) key is used for encryption and decryption.

(Modification 3)
In the description of FIG. 4, the user terminal 3 transmits the captured image data Im necessary for generating the transaction information Ia to the service provider server 1 in step S108. Instead of this, the user terminal 3 may encrypt the record of the input by the keyboard on the transaction screen and transmit it to the service provider server 1 instead of the captured image data Im. In this case, for example, the service provider server 1 generates transaction information Ia based on the keyboard input record character string obtained by decrypting the encrypted keyboard input record information.

(Modification 4)
The service provider server 1 may execute the transaction with reference to the transaction information Ia without determining whether or not the transaction information Ia and the transaction information Ib have the same contents in step S113 in FIG. That is, in this case, the service provider server 1 regards the transaction information Ia as more reliable information than the transaction information Ib, and executes the transaction indicated by the transaction information Ia. In this case, the service provider server 1 may not execute the transaction information Ib extraction process in step S112 in addition to step S113.

(Modification 5)
In the above embodiment, the process of determining whether the transaction information Ia and Ib have the same content is performed by the service provider server, but it is not always necessary and may be performed by another server. The attacker may also monitor the service provider server and may tamper with the transaction information Ia and Ib. In such a case, a separate server is provided so that the transaction information Ia is transmitted to the separate server after capture. Further, the transaction information Ib is transmitted to the other server via the service provider server. The separate server may determine the identity of the transaction information Ia and Ib and transmit the determination result to the service provider server side. By doing in this way, even if an attacker alters the contents of the transaction information Ib, the transaction information Ia can be prevented from being falsified, and illegal transactions can be suitably prevented.

DESCRIPTION OF SYMBOLS 1 ... Service provider server 2 ... Communication network 3 ... User terminal 4 ... Attacker server

Claims (12)

A transaction system comprising a server that executes a process related to a transaction, and a terminal that instructs the server to execute the process related to the transaction,
The terminal
Display control means for displaying a transaction screen for inputting the details of the transaction;
First transmission control means for transmitting input information indicating transaction details input on the transaction screen to the server;
Second transmission control means for transmitting image data of the transaction screen after transaction details are input to the server;
With
The server
If the transaction content indicated by the input information received from the first transmission control means is different from the transaction content extracted from the image data received from the second transmission control means, the execution of the processing related to the transaction is stopped. A transaction system comprising illegal transaction detection means. The terminal includes a storage unit that stores a first program for display and a second program different from the first program,
The transaction system according to claim 1, wherein the display control unit and the first transmission control unit are configured by the first program, and the second transmission control unit is configured by the second program. The terminal includes a storage unit that stores a third program,
The transaction system according to claim 1, wherein the display control unit, the first transmission control unit, and the second transmission control unit are configured by the third program. The second transmission control means transmits image data obtained by capturing the transaction screen after transaction details are input to the server,
The said unauthorized transaction detection means recognizes the said transaction content by performing a character recognition process with respect to the image data received from the said 2nd transmission control means, The any one of Claims 1-3 characterized by the above-mentioned. The trading system described in. The second transmission control means transmits image data in which character data input to the transaction screen is embedded to the server,
The said unauthorized transaction detection means recognizes the said transaction content based on the said character data extracted from the image data received from the said 2nd transmission control means, The Claim 1 characterized by the above-mentioned. Trading system. The storage unit of the terminal stores an encryption key for performing encryption and / or attaching a message authentication code,
The server includes a storage unit that stores a decryption key for decrypting data encrypted with the encryption key and / or verifying the message authentication code,
The second transmission control means encrypts the image data with the encryption key and / or transmits the image data with a message authentication code,
The unauthorized transaction detection means decrypts the image data received from the second transmission control means with the decryption key and / or verifies the message authentication code attached to the image data. Item 6. The transaction system according to any one of Items 1 to 5. The storage unit of the terminal stores an encryption key different from an encryption key stored in another terminal that instructs the server to execute a process related to a transaction,
The transaction system according to claim 6, wherein the storage unit of the server stores a different decryption key for each terminal. The second transmission control means transmits information related to the previous transaction in addition to the image data,
8. The fraudulent transaction detection means determines whether the fraudulent transaction is based on the image data received from the second transmission control means and information related to the previous transaction. The transaction system according to any one of the above. The second transmission control means transmits a predetermined character string in addition to the image data,
8. The fraudulent transaction detection unit determines whether the fraudulent transaction is based on the image data received from the second transmission control unit and the predetermined character string. The transaction system according to any one of the above. A program executed by a terminal having a computer,
Display control means for displaying a transaction screen for inputting the details of the transaction;
First transmission control means for transmitting input information indicating transaction details input on the transaction screen to a server that executes processing relating to the transaction ;
A program that causes the computer to function as second transmission control means for transmitting image data of the transaction screen after transaction details are input to the server. It is executed by a terminal that has a computer and displays a transaction screen for inputting transaction details and transmits input information indicating transaction details input on the transaction screen to a server that executes processing relating to the transaction A program,
A program for causing the computer to function as transmission control means for transmitting image data of the transaction screen after transaction details are input to the server.   A program that causes a computer to function as the server according to any one of claims 1 to 9.