Patent Publication Number: US-7912789-B2

Title: Electronic value, electronic purse device, and system for using the same

Description:
TECHNICAL FIELD 
     The present invention relates to a technique for using an electronic value that is information representing a value electronically. 
     BACKGROUND ART 
     Following advancements in information security techniques such as cryptology techniques and digital signature techniques, progress has been made in research and development to make electronic money a viable substitute for currency, and such electronic money is already in actual use to some extent. 
     Patent Document 1 discloses a technique that aims to realize safe circulation of electronic money deposited in an IC card. With an object of performing online transfer of electronic money from an electronic purse to an IC card and from a bank account to the electronic purse while ensuring high reliability, this document discloses a technique for transferring from an account at a financial institution to an electronic purse, and transferring electronic money from the electronic purse to an IC card inserted in the electronic purse. Here, after the IC card which has had the electronic money deposited therein is removed from the electronic purse, the balance of the IC card is automatically extinguished therefrom if account settlement using the electronic money is not performed within a certain length of time. 
     Patent Document 2 discloses a theft prevention system that, with a simple structure, enables a location of a theft prevention target object that has been stolen or lost to be specified. This is realized by mounting a wireless communication device in the theft prevention target object. The wireless communication device conforms to a communication format of a simple mobile phone system, and transmits its own terminal identification number with a predetermined timing. The location of the theft prevention target object is managed by managing the location of the wireless communication device based on the terminal identification number received from the wireless communication device and a base station identification number of a base station that received the terminal identification number. 
     Patent Document 1: Japanese Patent Application Publication No. 2004-139604 
     Patent Document 2: Japanese Patent Application Publication No. H09-128663 
     DISCLOSURE OF THE INVENTION 
     Problem to be Solved by the Invention 
     Although electronic money can be handled securely to a certain extent with the conventional techniques, progress is currently being made with respect to techniques for using electronic money, and there are demands for development of various techniques that enable electronic money to be used securely and reliably. 
     In response to such demands, the present invention has an object of providing an electronic value, an electronic value usage system, an electronic purse apparatus, a account settlement apparatus, and an electronic value management method and a computer program used in an electronic purse apparatus, all of which are capable of preventing dishonest use of an electronic value recorded on a recording medium such as a memory card that stores the electronic value that is information expressing a value electronically, even if the recording medium is lost or stolen. 
     Means to Solve the Problem 
     In order to achieve the stated object, the present invention is an electronic value usage system for using an electronic value that is information representing a value electronically, the electronic value usage system including: an acquisition unit operable to acquire value information; a first generation unit operable to generate a first authenticator with use of the value information and first data acquired when storing the value information; a storage unit operable to store the value information and the first authenticator in correspondence with each other as an electronic value; a second generation unit operable to generate a second authenticator with use of the value information and second data acquired when a user uses the electronic value; a judgment unit operable to judge whether or not the first authenticator and the second authenticator match each other; and a permission unit operable to, when the first authenticator and the second authenticator are judged to match each other, permit usage of, from among the electronic value, a usage value desired by the user. 
     EFFECTS OF THE INVENTION 
     With the stated structure, use of the usage value is permitted when the first authenticator and the second authenticator match. Here, if the user at the time of acquiring the electronic value and the user at the time of using the electronic value are the same person, identical first data and second data will be able to be provided, and therefore the first authenticator and the second authenticator will of course match. 
     However, if the storage unit that stores the electronic value is lost or stolen, a person who attempts to dishonestly use the electronic value stored in the storage unit does not know the first data. Consequently, the possibility that the first data and the second data will match is low, and the possibility that the first authenticator and the second authenticator will match is low. This means that use of the electronic value will not be permitted, and enables the electronic value to be protected from dishonest use. 
     Here, the electronic value usage system may include an electronic purse apparatus and an account settlement apparatus, wherein the electronic purse-apparatus includes the acquisition unit, the first generation unit, the storage unit and the second generation unit, and the account settlement apparatus includes the judgment unit and the permission unit. 
     With the stated structure, the account settlement apparatus permits use of the usage value when the first authenticator and the second authenticator are judged to match. This prevents dishonest account settlement being made with a dishonestly used electronic value. 
     Here, the electronic value usage system may be an electronic purse apparatus that is a portable IC card. 
     With the stated structure, the usage system is easily portable. 
     Furthermore, the present invention is an electronic purse apparatus that stores and manages an electronic value that is information representing a value electronically, the electronic purse apparatus including: an acquisition unit operable to acquire value information; a first generation unit operable to generate a first authenticator with use of the value information and first data acquired when storing the value information; a storage unit operable to store the value information and the first authenticator in correspondence with each other as an electronic value; a second generation unit operable to generate a second authenticator with use of the value information and second data acquired when a user uses the electronic value; a judgment unit operable to judge whether or not the first authenticator and the second authenticator match each other; and an output unit operable to, when the first authenticator and the second authenticator are judged to match each other, output, from among the electronic value, a usage value desired by the user. 
     With the stated structure, use of the usage value is permitted when the first authenticator and the second authenticator match. As described earlier, use of the electronic value will not be permitted if the electronic purse apparatus that stores the electronic value is lost or stolen, and therefore the electronic value can be protected from dishonest use. 
     Here, the first generation unit may include: a first data acquisition sub-unit operable to acquire the first data; and a first authenticator generation sub-unit operable to generate the first authenticator by subjecting the value information to one of encryption and digital signature, with use of the acquired first data, and the second generation unit may include: a second data acquisition sub-unit operable to acquire the second data; and a second authenticator generation sub-unit operable to generate the second authenticator by subjecting the value information to one of encryption and digital signature, with use of the acquired second data. 
     With the stated structure, the authenticators can be generated reliably using encryption or a digital signature. 
     Here, when an entire value shown by the value information is used, the output unit may output the value information as the usage value information, and deletes the electronic value from the storage unit. 
     With the stated structure, the whole of the electronic value can be used. 
     Here, the electronic purse apparatus may further include: a calculation unit operable to, when a partial value that is part of the value shown by the value information is used, subtract the partial value from the value shown by the value information, thereby calculating a remaining value; and a third generation unit operable to generate a third authenticator with use of the second data and the calculated remaining value, wherein the storage unit further stores, in place of the electronic value, the remaining value and the third authenticator in correspondence with each other as a new electronic value. 
     With the stated structure, a partial value that is part of the electronic value can be used. 
     Here, the acquisition unit may further acquire other value information, the first generation unit may further generate a third authenticator using the acquired first data and the other value information, the storage unit may further store the other value information and the third authenticator in correspondence as another electronic value, and the output unit, when the user desires to use one or more electronic values, may output respective value information of the one or more electronic values, as the usage value information, and delete the one or more electronic values from the storage unit. 
     With the stated structure, a plurality of electronic values can be stored and managed in the electronic purse apparatus. 
     Furthermore, the present invention is an electronic purse apparatus that stores and manages an electronic value that is information representing a value electronically, the electronic purse apparatus including: an acquisition unit operable to acquire value information; a first generation unit operable to generate a first authenticator with use of the value information and first data acquired when storing the value information; a storage unit operable to store the value information and the first authenticator in correspondence with each other as an electronic value; a second generation unit operable to generate a second authenticator with use of the value information and second data acquired when a user uses the electronic value; and an output unit operable to output the value information, the first authenticator, and the second authenticator. 
     With the stated structure, in the account settlement apparatus that receives the first authenticator and the second authenticator from the electronic purse apparatus, dishonest usage of the electronic value can be prevented by permitting use of the electronic value when the first authenticator and the second authenticator match. 
     Here, the first generation unit may include: a first data acquisition sub-unit operable to acquire the first data; and a first authenticator generation sub-unit operable to generate a first private key from the acquired first data, and generate the first authenticator by subjecting the value information to a public key method digital signature with use of the generated first private key, and the second generation unit may include: a second data acquisition sub-unit operable to acquire the second data; a second authenticator generation sub-unit operable to generate a second private key from the acquired second data, and generate the second authenticator by subjecting the value information to the public key method digital signature with use of the generated second private key; and a public key generation sub-unit operable to generate a public key from the generated second private key, and the output unit further outputs the generated public key. 
     With the stated structure, in the account settlement apparatus that receives the first authenticator, the second authenticator and the public key from the electronic purse apparatus, dishonest usage of the electronic value can be prevented by permitting use of the electronic value both when the first authenticator and the second authenticator match and verification of the second authenticator according to the public key succeeds. 
     Furthermore, the present invention is an electronic purse apparatus that stores and manages an electronic value that is information representing a value electronically, the electronic purse apparatus including: a data storage unit operable to store in advance first data acquired from a user; an acquisition unit operable to acquire value information; a storage unit operable to store the acquired value information; an acquisition unit operable to acquire second data from the user when the user uses the electronic value; a judgment unit operable to judge whether or not the first data and the second data match each other; a signature unit operable to, when the first data and the second data are judged to match each other, generate value authentication information corresponding to the stored value information or part thereof; and an output unit operable to output the value information or the part thereof, and the generated value authentication data. Furthermore, the present invention is an account settlement apparatus that performs account settlement processing using a received electronic value, the account settlement apparatus including: an acquisition unit operable to acquire, from the above-described electronic purse apparatus, the value information, the first authenticator and the second authenticator; a judgment unit operable to judge whether or not the first authenticator and the second authenticator match each other; and an account settlement unit operable to, when the first authenticator and the second authenticator are judged to match each other, perform account settlement processing with use of a usage value desired by the user. 
     With the stated structure, the value information is output when the stored first data and the input second data match. This prevents the electronic value being output dishonestly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a system structure diagram showing the structure of an electronic money usage system  10 ; 
         FIG. 2  is a block diagram showing the structure of a bank server apparatus  100 ; 
         FIGS. 3A to 3D  show examples of the data structure of cash-type and signature-type electronic money;  FIG. 3A  shows an example of the data structure of signature-type electronic money before a first authenticator and a second authenticator are written thereto; 
         FIG. 3B  shows an example of the data structure of signature-type electronic money when the first authenticator has been written thereto; 
         FIG. 3C  shows an example of the data structure of signature-type electronic money when the first authenticator and the second authenticator have been written thereto; 
         FIG. 3D  shows an example of the data structure of cash-type electronic money, or signature-type electronic money after being converted to cash-type electronic money; 
         FIG. 4  is a block diagram showing the structure of a mobile phone  200 ; 
         FIG. 5  is a block diagram showing the structure of a memory card  300 ; 
         FIG. 6  is a block diagram showing the structure of a register apparatus  400 ; 
         FIG. 7  is a flowchart showing operations for electronic money acquisition in the electronic money usage system  10 , and continues in  FIG. 8 ; 
         FIG. 8  is a flowchart showing operations for electronic money acquisition in the electronic money usage system  10 , and continues in  FIG. 9 ; 
         FIG. 9  is a flowchart showing operations for electronic money acquisition in the electronic money usage system  10 , and continues from  FIG. 8 ; 
         FIG. 10  is a flowchart showing operations for using electronic money in the electronic money usage system  10 , and continues in  FIG. 11 ; 
         FIG. 11  is a flowchart showing operations for using electronic money in the electronic money usage system  10 , and continues in  FIG. 12 ; 
         FIG. 12  is a flowchart showing operations for using electronic money in the electronic money usage system  10 , and continues from  FIG. 11 ; 
         FIG. 13  is a flowchart showing operations for using electronic money in an electronic money usage system  10   a  that is a modification of the electronic money usage system  10 ; 
         FIG. 14  is a flowchart showing operations for using electronic money in the electronic money usage system  10 , in particular operations when using part of an amount included in electronic money, and continues in  FIG. 15 ; 
         FIG. 15  is a flowchart showing operations for using electronic money in the electronic money usage system  10 , in particular operations when using part of an amount included in electronic money, and continues from  FIG. 14 ; 
         FIGS. 16A to 16C  show examples of the data structure of electronic money in the case of using part of an amount included in electronic money; 
         FIG. 16A  shows an example of the data structure of electronic money before use; 
         FIG. 16B  shows an example of the data structure of electronic money that includes a balance after usage; 
         FIG. 16C  shows an example of the data structure of electronic money that includes a used amount; and 
         FIG. 17  shows an example of the data structure of electronic money in the case of one piece of electronic money including a plurality of amounts. 
     
    
    
     DESCRIPTION OF NUMERIC REFERENCES 
     
         
         
           
               10  Electronic money usage system 
               10   a  Electronic money usage system 
               20  Internet 
               30  Mobile phone network 
               40  Radio base station 
               100  Bank server apparatus 
               101  Control unit 
               102  Information storage unit 
               103  Display unit 
               104  Input unit 
               105  Transmission/reception unit 
               106  Authentication unit 
               200  Mobile phone 
               201  Antenna 
               202  Communication unit 
               203  Communication control unit 
               204  Speaker 
               205  Microphone 
               206  Control unit 
               207  Input unit 
               208  Display unit 
               209  Input/output unit 
               300  Memory card 
               301  Input/output unit 
               302  Control unit 
               303  Authentication unit 
               304  Information storage unit 
               400  Register apparatus 
               401  Key storage unit 
               402  Authentication unit 
               403  Input unit 
               404  Display unit 
               405  Display unit 
               406  Control unit 
               407  Printing unit 
               408  Cash compartment 
               409  Information storage unit 
               410  Input/output unit 
               411  Cable 
           
         
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     1. Electronic Money Usage System  10   
     The following describes an electronic money usage system  10  as a first embodiment of the present invention. 
     1.1 Structure of the Electronic Money Usage System  10   
     As shown in  FIG. 1 , the electronic money usage system  10  is composed of a bank server apparatus  100 , a mobile phone  200 , a memory card  300  that is a portable medium, and a register apparatus  400 . The bank server apparatus  100  and the mobile phone  200  are connected via the Internet  20 , a mobile phone network  30  and a radio base station  40 . 
     The bank server apparatus  100  provides either cash-type electronic money or signature-type electronic money to a user in response to a request from the user. Cash-type and signature-type electronic money are described later. 
     When the user requests cash-type electronic money, the mobile phone  200  securely and reliably acquires cash-type electronic money of an amount requested by the user according to a user instruction, from the bank server apparatus  100  via the Internet  20 , the mobile phone network  30  and the radio base station  40 . The mobile phone  200  writes the acquired cash-type electronic money to the memory card  300 . 
     Next, when the user purchases a product or receives provision of a service and performs account settlement for the product or service using the cash-type electronic money, the memory card  300  to which the electronic money has been written is mounted in an input/output unit  410  of the register apparatus  400 . The register apparatus  400  receives the electronic money from the memory card  300  via the input/output unit  410 , and performs the account settlement using the received electronic money. At this time the memory card  300  deletes the stored electronic money. 
     When the user requests signature-type electronic money, the mobile phone  200  securely and reliably obtains cash-type electronic money of an amount requested by the user according to a user instruction, from the bank server apparatus  100  via the Internet  20 , the mobile phone network  30  and the radio base station  40 . The mobile phone  200  then receives input of a first password from the user, generates a first authenticator with use of the input first password, writes the generated first authenticator into the obtained electronic money, and writes the electronic money including the first authenticator to the memory card  300 . 
     When the user purchases a product or receives provision of a service and performs account settlement for the product or service using the cash-type electronic money, the memory card  300  to which the electronic money has been written is mounted in an input/output unit  410  of the register apparatus  400 . The input/output unit  410  receives input of a second password from the user, and outputs the received second password securely to the memory card  300 . The memory card  300  receives the second password securely, and generates a second authenticator using the received second password. The memory card  300  then judges whether or not the first authenticator included in the stored electronic money matches the generated second authenticator, and when the two are judged to match, transmits the electronic money securely and reliably to the register apparatus  400 . At this time, the memory card  300  deletes the stored electronic money. The register apparatus  400  receives the electronic money and performs the account settlement using the received electronic money. 
     1.2 Structure of the Bank Server Apparatus  100   
     As shown in  FIG. 2 , the bank server apparatus  100  is composed of a control unit  101 , an information storage unit  102 , a display unit  103 , an input unit  104 , a transmission/reception unit  105  and an authentication unit  106 . 
     The bank server apparatus  100  is a computer system specifically composed of a microprocessor, a ROM, a RAM, a hard disk unit, a communication unit, a display unit, a keyboard, a mouse, and the like. Computer programs are stored in the RAM or the hard disk unit. The compositional elements of the bank server apparatus  100  achieve their functions by the microprocessor operating according to the programs. 
     (1) Information Storage Unit  102   
     The information storage unit  102  stores in advance a user information table  121 , amount screen information  131 , a bank private key  141 , and an issued money table  151 . 
     The amount screen information  131  is information that composes a screen that is displayed by the mobile phone  200  and is for receiving input of an electronic money type and an electronic money amount. 
     Here, the electronic money type is information showing whether the electronic money is cash-type of signature-type. 
     The bank private key  141  is a private key in the bank server apparatus  100 , and is key data that is 160 bits in length. 
     The user information table  121  includes a plurality of pieces of user information, each of which corresponds to a user and includes information such as a user ID, a user public key, and other information. Here, the user ID is identification information identifying a user. The user public key is a public key that is generated based on a public key generation algorithm of public key encryption, using a user private key allocated to the memory card of the user as a basis. The user public key is key data of 160 bits in length. Here, the public key algorithm is based on elliptic curve encryption. Since elliptic curve encryption is commonly known, a detailed description thereof is omitted here. One example of the other information is contact details of the user. 
     The issued electronic money table  151  includes a plurality of pieces of issued information, each of which corresponds to electronic money already issued, and includes an electronic money ID, a user ID, an amount, an issue date, and a reissue section. Here, the electronic money ID is identification information identifying the corresponding electronic money. The user ID is identification information identifying the user who requested issue of the corresponding electronic money. The amount shows the amount of the corresponding electronic money. The issue date shows the date on which the corresponding electronic money was issued. The reissue section shows whether or not the corresponding electronic money has been reissued. The reissue section can have a value of either “0” or “1”, with the value of “0” showing that the corresponding electronic money has not been reissued, and the value of “1” showing that the corresponding electronic money has been reissued. 
     (2) Transmission/Reception Unit  105   
     The transmission/reception unit  105  is connected to the mobile phone  200  via the Internet  20 , the mobile phone network  30  and the wireless base station  40 . The transmission/reception unit  105  performs transmission/reception of information between the mobile phone  200  and the control unit  101 , between the mobile phone  200  and the authentication unit  106 , and between the mobile phone  200  and the information storage unit  102 . 
     (3) Authentication Unit  106   
     Based on an instruction from the control unit  101 , the authentication unit  106  performs mutual device authentication with the memory card  300  via the transmission/reception unit  105 , the Internet  20 , the wireless base station  40  and the mobile phone  200 , and if the mutual device authentication succeeds, the authentication unit  106  also performs key sharing. A session key is generated as a result of this key sharing. Here, device authentication is challenge-response authentication. Since challenge-response authentication is commonly known, a detailed description thereof is omitted here. 
     The authentication unit  106  outputs an authentication result showing a result of the mutual device authentication, in other words, whether the mutual device authentication has succeeded or failed, to the control unit  101 . When the result of the mutual device authentication shows success, the authentication unit  106  further outputs the generated session key to the control unit  101  if a session key has been generated. 
     Note that since mutual device authentication and key sharing are commonly known, a detailed description thereof is omitted here. 
     (4) Control Unit  101   
     (Mutual Authentication and Key Sharing) 
     The control unit  101  receives a connection instruction instructing connection of the bank sever apparatus  100  and the memory card  300 . 
     Having received the connection instruction, the control unit  101  instructs the authentication unit  106  to perform mutual device authentication, and further instructs the authentication unit  106  to perform key sharing in the case that mutual device authentication succeeds. The control unit  101  then receives the authentication result from the authentication unit  106 , and receives the session key in the case that device authentication has been successful. The control unit  101  also transmits the authentication result to the mobile phone  200 . 
     When the authentication result shows failure, the control unit  101  ends the electronic money acquisition-processing. 
     (User ID Search) 
     When the authentication result shows success, the control unit  101  receives a user ID identifying the user of the memory card  300  from the memory card  300  via the mobile phone  200 , the radio base station  40 , the mobile phone network  30 , the Internet  20  and the transmission/reception unit  105 . The control unit  101  then searches the user information table  121  stored in the information storage unit  102  for a user ID that matches the received user ID. When the received user ID does not exist in the user information table  121 , the control unit  101  transmits a message to that effect to the mobile phone  200 , and ends the electronic money acquisition processing. 
     (Transmission of Amount Screen Information) 
     When the received user ID exists in the user information table  121 , the control unit  101  reads the amount screen information  131  from the information storage unit  102  and transmits the read amount screen information  131  to the mobile phone  200  via the transmission/reception unit  105 , the Internet  20 , the mobile phone network  30  and the radio base station  40 . 
     (Verification of Amount Signature Data) 
     Next, the control unit  101  receives the type of the acquired electronic money, amount information showing the amount of the electronic money, and amount signature data generated for the amount information, from the memory card  300  via the mobile phone  200 , the radio base station  40 , the mobile phone network  30 , the Internet  20  and the transmission/reception unit  105 . The control unit  101  reads the user public key corresponding to the received user ID, and performs verification of the received amount signature data by subjecting the received amount information and amount signature data to a digital signature verification algorithm. Note that since digital signature verification algorithms are commonly known, a detailed description thereof is omitted here. 
     When the verification fails, the control unit  101  transmits a message to that effect to the mobile phone  200 , and ends the electronic money acquisition processing. 
     (Generation of Signature-Type and Cash-Type Electronic Money) 
     When the verification succeeds, the control unit  101  judges which of cash-type or signature-type the received electronic money is. When the received electronic money type is judged to be cash-type, the control unit  101  generates cash-type electronic money as described below. When the received electronic money type is judged to be signature-type, the control unit  101  generates signature-type electronic money as described below. 
     Here, as shown in the examples in  FIGS. 3A ,  3 B,  3 C and  3 D, both the cash-type and the signature-type electronic money are composed of an identification flag, an electronic money ID, an amount, a first authenticator, and a second authenticator. 
     The identification flag is a flag showing whether the corresponding electronic money is cash-type or is signature-type. The identification flag being “0” shows that the electronic money is cash-type, and the identification flag being “1” shows that the electronic money is signature-type. 
     The electronic money ID has a fixed value in the case of the corresponding electronic money being cash-type. Specifically, the electronic money ID is “0x00”. Note that in the present Description, “0x” indicates a value expressed according to hexadecimal notation. In the case of the corresponding electronic money being signature-type, the electronic money ID is identification information identifying the electronic money. 
     The amount shows a value of the corresponding electronic money as currency in the case of electronic money being used as currency. 
     The first authenticator and the second authenticator each have a fixed value in the case of the corresponding electronic money being cash-type. Specifically, the first authenticator and the second authenticator each have a value “0x0000”. In the case of the corresponding electronic money being signature-type, the first authenticator and the second authenticator are authentication-use data that has been generated based on a password input by the user, and the identification flag, the electronic money ID and the amount included in the electronic money. Details of how the of the first authenticator and the second authenticator are generated are given later. 
     (Generation of Cash-Type Electronic Money) 
     When the electronic money type is judged to be cash-type, the control unit  101  generates electronic money composed of an identification flag having a value “0”, an electronic money ID having a value “0x00”, an amount that is the amount information received from the memory card  300 , and a first authenticator and a second authenticator each having a value “0x0000”. The electronic money generated here is cash-type. 
     One example of cash-type electronic money is shown in  FIG. 3D . The electronic money shown in  FIG. 3D  is composed of a flag identifier “0”, an electronic money identifier “0x00”, an amount “10000”, a first authenticator “0x0000” and a second authenticator “0x0000”. 
     (Generation of Signature-Type Electronic Money) 
     When the electronic money type is judged to be signature-type, the control unit  101  generates electronic money composed of an identification flag having a value “1”, an electronic money ID having a value that uniquely identifies the electronic money, and an amount that is the amount information received from the memory card  300 , and the first authenticator and the second authenticator left blank. The electronic money generated here is signature-type. 
     One example of signature-type electronic money is shown in  FIG. 3A . Electronic money  501  shown in  FIG. 3A  is composed of an identification flag “1”, an electronic money ID “0x0F”, an amount “10000”, a first authenticator “blank” and a second authenticator “blank”. 
     (Generation and Transmission of Electronic Money Signature Data) 
     The control unit  101  reads the bank private key  141  from the information storage unit  102 , and generates electronic money signature data by subjecting the generated cash-type or signature-type electronic money to a digital signature with use of the read bank private key  141 . The control unit  101  then transmits the generated electronic money signature data and the generated cash-type or signature-type electronic money to the memory card  300  via the transmission/reception unit  105 , the Internet  20 , the mobile phone network  30 , and the mobile phone  200 . 
     (5) Input Unit  104  and Display Unit  103   
     The input unit  104  receives an instruction or input of information from an operator of the bank server apparatus  100 , and outputs the received instruction or input information to the control unit  101 . 
     The display unit  103  displays various information under the control of the control unit  101 . 
     1.3 Structure of the Mobile Phone  200   
     As shown in  FIG. 4 , the mobile phone  200  is composed of an antenna  201 , a communication unit  202 , a communication control unit  203 , a speaker  204 , a microphone  205 , a control unit  206 , an input unit  207 , a display unit  208 , and an input/output unit  209 . 
     The mobile phone  200  is a computer system specifically composed of a microprocessor, a signal processor, a ROM, a RAM, and the like. Computer programs are stored in the RAM. The compositional elements of the mobile phone  200  achieve part of their functions by the microprocessor and the signal processor operating according to the computer programs. 
     (1) Antenna  201 , Communication Unit  202 , Communication Control Unit  203   
     The communication unit  202  amplifies a radio frequency signal received by the antenna  201 , converts the output signal to an IF signal, amplifies the IF signal, and demodulates amplified IF signal to a baseband signal. The communication unit  202  also modulates a high frequency signal according to a baseband signal, converts the output thereof to a radio frequency, and outputs the resultant radio frequency signal to the antenna  201 . The communication control unit  203  generates a baseband signal and outputs the generated baseband signal to the communication unit  202 , and the communication unit  202  receives the output baseband signal. 
     In this way, the communication control unit  203 , the communication unit  202  and the antenna  201  perform transmission/reception of information with the bank server apparatus  100  via the radio base station  40 , the mobile phone network  30  and the Internet  20 . 
     (2) Input Unit  207  and Display Unit  208   
     The input unit  207  receives an instruction from the user of the mobile phone  200 , and outputs the received instruction to the control unit  206 . 
     The display unit  208  displays various information under the control of the control unit  206 . 
     (3) Input/Output Unit  209   
     When the memory card  300  is mounted in the mobile phone  300 , the input/output unit  209  performs transmission/reception of information between the control unit  206  and the memory card  300  under the control of the control unit  206 . 
     (4) Control Unit  206   
     (Output of a Connection Instruction) 
     Upon receiving a connection instruction from the user via the input unit  207 , the control unit  206  outputs the connection instruction to the memory card  300  via the input/output unit  209 . Furthermore, control unit  202  outputs the connection instruction to the bank server apparatus  100  via the communication control unit  203 , the communication unit  202 , the antenna  201 , the radio base station  40 , the mobile phone network  30  and the Internet  20 . 
     (Relay of Information) 
     After outputting the connection instruction, the control unit  206  relays transmission/reception of information between the memory card  300  and the bank server apparatus  100 . 
     Specifically, the control unit  206  relays transmission/reception of various information between the bank server apparatus  100  and the memory card  300  when the bank server apparatus  100  and the memory card  300  perform mutual authentication and key sharing. 
     Furthermore, upon receiving a user ID from the memory card  300 , the control unit  206  transmits the received user ID to the bank server apparatus  100 . 
     Upon receiving a type, amount information and amount signature data from the memory card  300 , the control unit  206  transmits the received type, amount information and amount signature data. 
     Upon receiving electronic money and electronic money signature data from the bank server apparatus  100 , the control unit  206  transmits the received electronic money and electronic signature data to the memory card  300 . 
     (Reception of Information from the Bank Server Apparatus  100  and the Memory Card  300 ) 
     After the bank server apparatus  100  and the memory card  300  have performed mutual authentication and key sharing, the control unit  206  receives either success or failure notification showing the result of mutual authentication from the bank server apparatus  100 , and receives either success or failure notification showing the result of mutual authentication from the memory card  300 . When failure notification is received from at least one of the bank server apparatus  100  and the memory card  300 , the control unit  206  outputs a message to that effect which it has displayed by the display unit  208 , and then ends the processing. When success notification is received from both the bank server apparatus  100  and the memory card  300 , the control unit  206  continues the processing. 
     If the user ID search result received from the bank server apparatus  100  is that the user ID does not exist in the user information table  121 , the control unit  206  receives error notification showing that the user ID does not exist in the user information  121 . On receiving the error notification, the control unit  206  outputs a message to that effect which it has displayed by the display unit  208 , and then ends the processing. 
     Furthermore, the control unit  206  receives amount screen information from the bank server apparatus  100 . On receiving the amount screen information, the control unit  206  generates an amount screen in accordance with the received amount screen information, and outputs the generated amount screen which it has displayed by the display unit  208 . The control unit  206  then receives amount information and an electronic money type from the input unit  207 , and outputs the received amount information and electronic money type to the memory card  300  via the input/output unit  209 . 
     If verification of the amount signature data fails, the control unit  206  receives, from the memory card  300 , failure information that is an amount signature data verification result and shows that verification has failed. On receiving the failure notification, the control unit  206  outputs a message to that effect which it has displayed by the display unit  208 , and then ends the processing. 
     If verification of the electronic money signature data fails, the control unit  206  receives failure information that is an electronic money signature data verification result and shows that verification has failed. On receiving the failure notification, the control unit  206  outputs a message to that effect which it has displayed by the display unit  208 , and then ends the processing. 
     The control unit  206  also receives a password request showing a request to input a first password from the memory card  300 . Here, the first password is, for instance, a four digit number that has been arbitrarily set by the user. On receiving the password request, the control unit  206  outputs a message to that effect which it has displayed by the display unit  208 , and receives the first password from the input unit  207 . The control unit  206  then subjects the received first password an encryption algorithm, thereby generating a first encrypted password, and outputs the generated first password to the memory card  300  via the input/output unit  209 . 
     1.4 Structure of the Memory Card  300   
     The memory card  300  is a resin plate of 32 mm in length, 24 mm in width and 2.1 mm in thickness, that has an IC chip sealed therein. As shown in  FIG. 5 , the memory card  300  is composed of an input/output unit  301 , a control unit  302 , an authentication unit  303 , and an information storage unit  304 . The memory card  300  is an electronic purse apparatus that stores and manages electronic money. 
     The memory card  300  is a computer system specifically composed of a microprocessor, a ROM, a RAM, and the like. Computer programs are stored in the RAM. The memory card  300  achieves its functions by the microprocessor operating in accordance with the computer programs. 
     The memory card  300  is mounted in either of the mobile phone  200  and the register apparatus  400  by the user. 
     The following describes each compositional elements of the memory card  300 . 
     (1) Information Storage Unit  304   
     As shown in  FIG. 5 , the information storage unit  304  stores a user ID  321 , a user private key  322 , a bank public key  325 , and a store public key  326 , and has an area for storing electronic money  323 ,  324  . . . . 
     The user ID  321  is identification information for identifying the user of the memory card  300 . 
     The user private key  322  is a private key allocated to the memory card  300 , and is key data of 160 bits in length. The bank public key  325  is a public key allocated to the bank server apparatus  100 , and the store public key  326  is a public key allocated to the register apparatus  400 . The bank public key  325  and the store public key  326  are each key data of 160 bits in length. 
     The bank public key  325  is a public key generated based on a public key generation algorithm using a bank private key as a basis. Similarly, the store public key  326  is a public key generated using a store private key as a basis. Here, the public key generation algorithm is based on elliptic curve encryption. Since elliptic curve encryption is commonly known, a detailed description thereof is omitted here. 
     Each of the electronic money  323 ,  324  . . . is cash-type electronic money or signature-type electronic money as described earlier. 
     An example of the cash-type electronic money stored in the information storage unit  304  is that shown in  FIG. 3D . Such cash-type electronic money is composed of an identification flag “0”, an electronic money ID “0x00”, an amount “10000”, and first authenticator “0x0000” and a second authenticator “0x0000”. 
     An example of the signature-type electronic money stored in the information storage unit  304  is, as shown in  FIG. 3B , composed of an identification flag “1”, an electronic money ID “0x0F”, an amount “10000”, a first authenticator “E 1 (PW 1 ,1∥0 x0F∥0000”, and a second authenticator “blank”. Here, the identification flag, the electronic money ID, the amount and the second authenticator are as described earlier. The first authenticator is described below. 
     Here, “E 1 (A,B)” is a cipher text obtained by subjecting data B to an encryption algorithm E 1  with use of a key A. “C∥D” shows concatenation of data C and data D in the stated order. One example of the encryption algorithm E 1  is an encryption algorithm conforming to DES (Data Encryption Standard). 
     (2) Authentication Unit  303   
     The authentication unit  303  performs mutual device authentication via the input/output unit  301  with an external apparatus in which the memory card  300  is mounted, according to an instruction from the control unit  302 , and also performs key sharing if the mutual device authentication succeeds. A session key is generated as a result of the key sharing. Here, the external apparatus is either of the bank server apparatus  100  and the register apparatus  400 . 
     The authentication unit  303  outputs an authentication result showing a result of the mutual device authentication, in other words, whether the mutual device authentication has succeeded or failed, to the control unit  302 . In the case of a session key being generated, the authentication unit  303  further outputs the generated session key to the control unit  302 . 
     Note that the device authentication is challenge-response authentication. Since challenge-response authentication is commonly known, a detailed description thereof is omitted here. Furthermore, since key sharing is commonly known, a detailed description thereof is omitted here. 
     (3) Input/Output Unit  301   
     Upon the memory card  300  being mounted in the external apparatus, the input/output unit  301  detects that the memory card  300  has been mounted in the external apparatus. Upon detecting the mounting, the input/output unit  301  notifies the control unit  302  by sending detection information showing detection of mounting thereto. At this time, the input/output unit  301  receives device information showing the external apparatus type. Here, the device information shows one of the mobile phone  200  and the register apparatus  400 . 
     Furthermore, when the memory card  300  is mounted in the external apparatus, the input/output unit  301  performs transmission/reception of information between the external apparatus and the control unit  302 , between the external apparatus and the authentication unit  303 , and between the external apparatus and the information storage unit  304 . 
     (4) Control Unit  302   
     The control unit  302  receives, from the input/output unit  301 , detection information showing the detection of the mounting, and further receives device information showing the external apparatus type. The control unit  302  then judges which of the mobile phone  200  and the register apparatus  400  is shown by the received device information. 
     (a) Acquisition of Electronic Money 
     When the received device information is judged to show the mobile phone  200 , the control unit  302  further receives a connection instruction showing connection with the bank server apparatus  100 , from the mobile phone  200 . 
     On receiving the connection instruction, the control unit  302  instructs the authentication unit  303  to perform mutual device authentication and key sharing with the bank server apparatus  100 . Next, the control unit  302  receives the mutual authentication result from the authentication unit  303 , and in the case that mutual authentication has succeeded, also receives a session key. Here, the mutual authentication result shows either of success or failure of authentication. The control unit  302  outputs the mutual authentication result to the mobile phone  200  via the input/output unit  301 . 
     In the case of the mutual authentication result showing failure, the control unit  302  ends the electronic money acquisition processing. 
     In the case of the mutual authentication result showing success, the control unit  302  reads the user ID  321  from the information storage unit  304 , and transmits the read user ID  321  to the bank server apparatus  100  via the input/output unit  301 , the mobile phone  200 , the radio base station  40 , the mobile phone network  30  and the Internet  20 . 
     Next, the control unit  302  receives the type of the electronic money to be obtained and amount information showing the amount of the electronic money, from the mobile phone  200  via the input/output unit  301 , and temporarily stores the received electronic money type and amount information internally. Next, the control unit  302  reads the user private key  322  from the information storage unit  304 , and subjects the received amount information to a digital signature with use of the read user private key  322 , thereby generating amount signature data. Next, the control unit  302  transmits the received type and amount information and the generated amount signature data to the bank server apparatus  100  via the input/output unit  301 , the mobile phone  200 , the radio base station  40 , the mobile phone network  30  and the Internet  20 . 
     Furthermore, the control unit  302  receives electronic money and electronic money signature data from the bank server apparatus  100  via the Internet  20 , the mobile phone network  30 , the radio base station  40 , the mobile phone  200  and the input/output unit  301 . The control unit  302  then reads the bank public key  325  from the information storage unit  304 , and subjects the received electronic money and electronic money signature data to digital signature verification with use of the read bank public key  325 , there by obtaining verification information. The verification result shows either of success or failure in verification. In the case of the verification result showing failure, the control unit  302  outputs failure notification showing failure, to the mobile phone  200  via the input/output unit  301 . In the case of the verification result showing success, the control unit  301  writes the received electronic money to the information storage unit  304 . 
     Next, the control unit  302  extracts the identification flag from the received electronic money, and judges which of “0” and “1” is shown by the identification flag. In the case of the identification flag being “0”, the electronic money is cash-type, and therefore the control unit  302  ends the electronic money acquisition processing. 
     In the case of the identification flag being “1”, the electronic money is signature-type, and therefore the control unit  302  makes a request, to the mobile phone  200  via the input/output unit  301 , for input of the first password. 
     Next, the control unit  302  receives the first encrypted password from the mobile phone  200 , and decrypts the received first encrypted password, thereby generating a first decrypted password. The control unit  302  extracts the identification amount, the electronic money ID and the amount from the received electronic money, bit concatenates the extracted identification amount, electronic money ID and amount in the stated order, thereby generating a concatenated entity, and subjects the generated concatenated entity to an encryption algorithm E 1  using the generated first decrypted password as a key, thereby generating a first authenticator. 
     first authenticator Sign 1 =E 1 (first decrypted password, identification flag∥electronic money ID∥amount) 
     Next, the control unit  302  overwrites the electronic money in the information storage unit  304  to include the generated first authenticator. 
     In this way, the electronic money received from the bank server apparatus  100  is written to the information storage unit  304 . At this time, in the case of the received electronic money being cash-type, the received electronic money is stored as is to the information storage unit  304 . In the case of the received electronic money being signature-type, the first authenticator in the received electronic money is rewritten with the first authenticator generated as described above. 
     (b) Usage of Electronic Money 
     When the received device information is judged to show the register apparatus  400 , the control unit  302  instructs the authentication unit  303  to performs mutual device authentication and key sharing with the register apparatus  400 . The control unit  302  then receives a mutual authentication result from the authentication unit  303 , and also receives a session key in the case that mutual authentication has succeeded. Here, the mutual authentication result shows either success or failure in authentication. 
     In the case of the mutual authentication result showing failure, the control unit  302  ends the electronic money usage processing. 
     On the other hand, in the case of the mutual authentication result showing success, the control unit  302  outputs, to the register apparatus  400  via the input/output unit  301 , success notification showing that the mutual authentication result is success. The control unit  302  also reads the user ID  321  from the information storage unit  304 , and transmits the read user ID  321  to the register apparatus  400  via the input/output unit  301 . 
     Next, the control unit  302  receives a sale amount and sale amount signature data from the register apparatus  400  via the input/output unit  301 . The sale amount is remuneration for a product that the user has purchased or a service that the user has been provided with by the store. The sale amount signature data is signature data generated with respect to the sale amount. Details of how the sale amount signature data is generated are given later. 
     Next, the control unit  302  reads the store public key  326  from the information storage unit  304 , and subjects the received sale amount and sale amount signature data to digital signature verification with use of the read store public key  326 , thereby obtaining a verification result. The verification result shows either success or failure in verification. In the case of the verification result showing failure, the control unit  302  outputs failure notification showing failure, to the register apparatus  400  via the input/output unit  301 . 
     In the case of a verification result showing success, the control unit  302  temporarily stores the received sale amount, and then searches the information storage unit  304  for electronic money that includes an amount that is the same as the amount shown by the sale amount. When electronic money that includes the same amount does not exist, the control unit  302  outputs a search result to that effect to the register apparatus  400  via the input/output unit  301 . 
     When electronic money that includes the same amount does exist, the control unit  302  extracts the identification flag from the electronic money, and judges which of “0” and “1” is shown by the extracted identification flag. 
     When the extracted flag is judged to show “0”, in other words when the electronic money is cash-type, the control unit  302  generates electronic money signature data with respect to the electronic money as described later, and outputs the electronic money and the electronic money signature data to the register apparatus  400  via the input/output unit  301 . 
     When the extracted flag is judged to show “1”, in other words when the electronic money is signature-type, the control unit  302  makes a request to the register apparatus  400  for input of the second password, then receives the second encrypted password from the register apparatus  400 , and decrypts the received second encrypted password, thereby generating a second decrypted password PW 2 . Next, from the electronic money that includes the same amount as the received sale amount, the control unit  302  extracts the identification flag, the electronic money ID and the amount, and bit concatenates the extracted identification flag, electronic money ID and amount in the stated order, thereby obtaining a concatenated entity. The control unit  302  then subjects the generated concatenated entity to the encryption algorithm E 1  with use of the generated second encrypted password PW 2 , thereby generating a second authenticator Sign 2 . 
     second authenticator Sign 2 =E 1  (second decrypted password PW 2 , identification flag∥electronic money ID∥amount) 
     Next, the control unit  302  overwrites in the electronic money in the information storage unit  304  so that the second authenticator therein in the generated second authenticator. Here, an example of the electronic money that includes the newly written second authenticator is shown in  FIG. 3C . The second authenticator in the electronic money  503  shown in  FIG. 3C  is 
     E 1 (PW 2 ,1∥0x0F∥10000). 
     Next, the control unit  302  extracts the first authenticator and the second authenticator from the electronic money, and judges whether or not the extracted first authenticator and the extracted second authenticator match each other. When the two do not match, the control unit  302  further performs a search of other electronic money. 
     When the two match, the control unit  302  sets the identification flag of the electronic money as “0”, the electronic money ID as “0x00”, the first authenticator as “0x0000”, and the second authenticator as “0x0000”. An example of the rewritten electronic money is shown in  FIG. 3D . Next, the control unit  302  reads the user private key  322  from the information storage unit  304 , and with use of the read user private key  322  subjects the electronic money whose identification flag, electronic money ID, first authenticator and second authenticator have been rewritten as described to a digital signature, thereby generating electronic money signature data. The control unit  302  outputs the rewritten electronic money and the generated electronic money signature data to the register apparatus  400  via the input/output unit  301 . 
     Next, the control unit  302  deletes the stored electronic money from the information storage unit  304 . 
     1.5 Structure of the Register Apparatus  400   
     The register apparatus  400  is a cash register that has functions such as performing account settlement of payment from a user, and safe-keeping the currency used for payment. As shown in  FIG. 6 , the register apparatus  400  is composed of a key storage unit  401 , an authentication unit  402 , an input unit  403 , a display unit  404 , a display unit  405 , a control unit  406 , a printing unit  407 , a cash compartment  408 , an information storage unit  409 , and an input/output unit  410 . 
     The register apparatus  400  is a computer system composed specifically of a microprocessor, a ROM, a RAM, a display unit, a keyboard, and the like. Computer programs are stored in the ROM. The register apparatus  400  achieves its functions by the microprocessor operating in accordance with the computer programs. 
     (1) Key Storage Unit  401   
     The key storage unit  401  is provided such that it cannot be accessed from outside, and, as shown in  FIG. 6 , the key storage unit  401  stores a store private key  471 . 
     The store private key  471  is a private key allocated to the register apparatus  400 , and is key data that is 160 bits in length. 
     (2) Information Storage Unit  409   
     The information storage unit  409  stores a user information table  431  as shown in  FIG. 6 . 
     The user information table  132  is composed of a plurality of pieces of user information, each of which corresponds to a different user. 
     Each piece of user information is composed of a user ID, a user public key and other information. The user ID is identification information for identifying a user. The user public key is a public key allocated to the memory card of the user, and is key data of 160 bits in length. The user public key is a public key generated based on the public key generation algorithm using the user private key as a basis. 
     (3) Authentication Unit  402   
     When the memory card  300  is mounted in the input/output unit  410  of the register apparatus  400 , the authentication unit  402  performs mutual device authentication with the memory card via the input/output unit  410  under the control of the control unit  406 , and when the mutual device authentication succeeds, further performs key sharing. A session key is generated as a result of this key sharing. Here, the device authentication is challenge-response authentication. Since challenge-response authentication is commonly known, a detailed description thereof is omitted here. 
     The authentication unit  402  outputs an authentication result showing a result of the mutual device authentication, in other words, showing success or failure in mutual device authentication, to the control unit  406 . When a session key has been generated, the authentication unit  402  further outputs the generated session key to the control unit  406 . 
     (4) Input/Output Unit  410   
     The input/output unit  410  has a connection unit in which the memory card  300  is mounted, and a numeric key pad composed of a plurality of keys on which numbers 0 to 9 and so on are inscribed. The input/output unit  410  is a device that is independent from the register apparatus  400 , and is connected via a cable  411  to the control unit  406  and the authentication unit  402  of the register apparatus  400 . 
     The memory card  300  is mounted in the input/output unit  410  by the user. 
     Upon mounting of the memory card  300  being detected, the input/output unit  410  outputs detection information showing the detection, to the control unit  406 . 
     The input/output unit  410  performs transmission/reception of information bi-directionally between the control unit  406  and the memory card  300  under the control of the control unit  406 , and between the authentication unit  402  and the memory card  300  under the control of the authentication unit  402 . 
     Furthermore, the input/output unit  410  receives input of a password according to a user operation of the numeric keys, and outputs the received password to the control unit  406 . 
     (5) Control Unit  406   
     The control unit  406  receives input of a sale amount from an operator of the register apparatus  400 . Next, the control unit  406  receives detection information showing detection of mounting of the memory card  300  from the input/output unit  410 . 
     On receiving the detection information, the control unit  406  controls the authentication unit  402  so as to perform mutual device authentication and key sharing with the memory card  300 . Next, the control unit  406  receives an authentication result from the authentication unit  402 . In the case of the authentication result showing failure, the control unit  406  outputs a message showing authentication failure to the display unit  404  and the display unit  405 , and instructs the display unit  404  and the display unit  405  to display the message. The control unit  406  then ends the electronic money usage processing. 
     In the case of the authentication result showing that device authentication with the memory card  300 , the control unit  406  receives success notification from the memory card  300  via the input/output unit  410 . 
     When the authentication result received from the authentication unit  402  shows success, but success notification is not received from the memory card  300  within a predetermined period of time from when device authentication takes place, the control unit  406  considers the device authentication to have failed, and outputs a message showing authentication failure to the display unit  404  and the display unit  405 , and instructs the display units  404  and  405  to display the message. The control unit  406  then ends the electronic money usage processing. 
     When the authentication result received from the authentication unit  402  shows success and success notification is received from the memory card  300  within the predetermined period from when the device authentication takes place, the control unit  406  further receives the user ID from the memory card  300 . 
     Next, the control unit  406  reads the store private key  471  from the key storage unit  401 , and with use of the read store private key  471 , subjects the sale amount of which input was received to a digital signature, thereby generating sale amount signature data. The control unit  406  then outputs the sale amount of which input was received and the generated sale amount signature data to the memory card  300  via the input/output unit  410 . 
     When failure notification showing that the result of sale amount signature data verification is failure is received from the memory card  300  within a predetermined time period from when the sale amount and the sale amount signature data have been output to the memory card  300 , the control unit  406  outputs a message to that effect to the display unit  404  and the display unit  405 , and instructs the display unit  404  and the display unit  405  to display the message. The control unit  406  then ends the electronic money usage processing. 
     When such failure notification is not received from the memory card  300  within a predetermined time period from when the sale amount and the sale amount signature data have been output to the memory card  300 , and additionally when an electronic money search result is received and the electronic money search result shows that electronic money does not exist, the control unit  406  outputs a message to that effect to the display unit  404  and the display unit  405 , and instructs the display unit  404  and the display unit  405  to display the message. The control unit  406  then ends the electronic money usage processing. 
     When a search result is not received, or when the received search result shows that electronic money exists, the control unit  406  further receives the second password from the memory card  300 , instructs the input/output unit  410  to receive input of the second password, and receives the second password from the input/output unit  410 . Next, the control unit  406  encrypts the received second password, thereby generating a second encrypted password, and outputs the generated second encrypted password to the memory card  300  via the input/output unit  410 . 
     The control unit  406  receives electronic money and electronic money signature data from the memory card  300  via the input/output unit  410 , reads the piece of user information that includes the received user ID from the user information table  431 , and extracts the user public key from the read user information. Next, the control unit  406  subjects the received electronic money and electronic money signature data to digital signature verification using the extracted user public key. In the case that verification fails, the control unit  406  outputs a message to that effect to the display unit  404  and the display unit  405 , and instructs the display unit  404  and the display unit  405  to display the message. Then control unit  406  then ends the electronic money usage processing. 
     In the case the verification succeeds, the control unit  406  writes the received electronic money to the information storage unit  409 , and performs sale account settlement processing using the received electronic money. 
     (8) Input Unit  403 , Display Unit  404 , Display Unit  405 , Printing Unit  407  and Cash Compartment  408   
     The input unit  403  receives input of various information from the operator of the register apparatus  400 , and outputs the received input to the control unit  406 . The display unit  404  and the display unit  405  receive information to the displayed from the control unit  406 , and display the received information. 
     The printing unit  407  prints various information under the control of the control unit  406 . 
     The cash compartment  408  safe-keeps bills, coins and so on. 
     1.6 Operations of the Electronic Money Usage System  10   
     The following describes operations of the electronic money usage system  10 , and in particular operations when acquiring electronic money and operations when using electronic money. 
     (1) Operations for Electronic Money Acquisition 
     The following describes operations for electronic money acquisition in the electronic money usage system  10 , with reference to the flowcharts shown in  FIG. 7  to  FIG. 9 . 
     The input unit  207  of the mobile phone  200  receives a connection instruction from the user (step S 101 ), and the control unit  206  outputs the connection instruction to the bank server apparatus  100  via the communication control unit  203 , the communication unit  202 , the antenna  201 , the radio base station  40 , the mobile phone network  30 , and the Internet  20  (step S 102 ). The control unit  206  also outputs the connection instruction to the memory card  300  via the input/output unit  209  (step S 103 ). 
     The authentication unit  106  of the bank server apparatus  100  and the authentication unit  303  of the memory card  300  perform mutual device authentication and key sharing (step S 104 ). 
     When the authentication unit  106  fails in authentication (step S 105 ), the control unit  101  notifies the mobile phone  200  of the failure (step S 106 ), and then ends the operations for electronic money acquisition. When the authentication unit  106  succeeds in authentication (step S 105 ), the control unit  101  notifies the mobile phone  200  of the success (step S 107 ). 
     When the authentication unit  303  fails in authentication (step S 108 ), the control unit  302  notifies the mobile phone  200  of the failure (step S 109 ), and then ends the operations for electronic money acquisition. When the authentication unit  303  succeeds in authentication (step S 108 ), the control unit  302  notifies the mobile phone  200  of the success (step S 110 ). 
     When the control unit  206  of the mobile phone  200  receives notice of authentication failure from at least one of the bank server apparatus  100  and the memory card  300  (step S 111 ), the display unit  208  displays a message to the effect (step S 112 ), and the control unit  206  ends subsequent electronic money acquisition processing. 
     When the authentication unit  303  succeeds in authentication (step S 108 ), the control unit  302  reads the user ID  321  from the information storage unit  304  (step S 113 ), and transmits the read user ID to the bank server apparatus  100  via the mobile phone  200  (step S 114  to step S 115 ). 
     When the authentication succeeds (step S 105 ), the control unit  101  receives the user ID from the memory card  300  (steps S 114  to S 115 ), and searches the user information table  121  for a user ID that matches the received user ID (step S 116 ). When the received user ID does not exist in the user information table  121  (step S 117 ), the control unit  101  transmits a message to that effect to the mobile phone  200  (step S 118 ), and ends the electronic money acquisition processing. 
     The control unit  206  of the mobile phone  200  receives a message (step S 118 ), and when the received message is error notification (step S 119 ), the display unit  208  displays a message to that effect (step S 120 ), and the control unit  206  ends the processing. 
     When the received user ID exists in the user information table  121  (step S 117 ), the control unit  101  reads the amount screen information  131  from the information storage unit  102  (step S 121 ), and transmits the read amount screen information  131  to the mobile phone  200  (step S 122 ). 
     Upon receiving the amount screen information from the bank server apparatus  100  (step S 122 ), the control unit  206  generates an amount screen in accordance with the received amount screen information, and the display unit  208  displays the amount screen (step S 123 ). The input unit  207  receives input of the amount information and the electronic money type (step S 124 ), and outputs the received amount information and electronic money type to the memory card  300  via the input/output unit  209  (step S 125 ). 
     Next, the control unit  302  receives the type and amount information from the mobile phone  200  (step S 125 ), and temporarily stores the received type and amount information internally (step S 126 ). Using the user private key  322 , the control unit  302  subjects the received amount information to a digital signature, thereby generating amount signature data (step S 127 ), and transmits the received type and amount information and the generated amount signature data to the bank server apparatus  100  (step S 128  to step S 129 ). 
     Next, the control unit  101  receives the type, the amount information and the amount signature data from the memory card  300  (steps S 128  to S 129 ), and using the user public key that corresponds to the received user ID, verifies the received amount signature data by subjecting the received amount information and amount signature data to a digital signature verification algorithm (step S 130 ). 
     When verification fails (step S 131 ), the control unit  101  transmits a message to that effect to the mobile phone  200  (step S 132 ), and ends the electronic money acquisition processing. 
     The control unit  206  receives a message from the bank server apparatus  100  (step S 132 ), and when the received message shows failure (step S 133 ), the display unit  208  displays a message to that effect (step S 134 ), and the control unit  206  ends the processing. 
     When verification succeeds (step S 131 ), the control unit  101  judges which of cash-type and signature-type the acquired electronic money type is, and when the acquired electronic money type is judged to be cash-type (step S 135 ), generates cash-type electronic money (step S 136 ). When the acquired electronic money type is judged to be signature-type (step S 135 ), the control unit  101  generates signature-type electronic money (step S 137 ). 
     Next, the control unit  101  generates electronic money signature data by subjecting the generated cash-type or signature-type electronic money to a digital signature with use of the bank private key  141  read from the information storage unit  102  (step S 141 ), and transmits the generated electronic money signature data and the generated cash-type or signature-type electronic data to the memory card  300  (step S 142  to step S 143 ). 
     Next, the control unit  302  receives the electronic money and the electronic money signature data from the bank server apparatus  100  (step S 142  to step S 143 ), subjects the received electronic money and electronic money signature data to digital signature verification with use of the bank public key  325  read from the information storage unit  304 , and obtains verification result showing either success or failure of verification (step S 144 ). The control unit  302  then outputs the verification result to the mobile phone  200  via the input/output unit  301  (step S 146 ). 
     The control unit  206  receives the verification result (step S 146 ), and transmits the received verification result to the bank server apparatus  100  (step S 158 ). 
     The control unit  101  receives the verification result (step S 158 ), and when the received verification result shows failure (step S 159 ), the control unit  101  does nothing. When the received verification result shows success (step S 159 ), the control unit  101  performs account settlement processing with the user of the memory card  300  based on the amount information received from the memory card  300 . As one example, the amount shown by the amount information is deducted from the bank account of the user of the memory card  300  (step S 161 ), and then the bank server apparatus  100  ends the electronic money provision processing. 
     The control unit  206  receives the verification result (step S 146 ), and when the received verification result shows failure (step S 147 ), the display unit  208  displays a message to that effect (step S 148 ), and the control unit  206  ends the processing. 
     When the verification result shows failure (step S 145 ), the control unit  302  ends the processing. 
     When the verification result shows success (step S 145 ), the control unit  302  writes the received electronic money to the information storage unit  304  (step S 149 ). 
     Next, the control unit  302  extracts the received electronic money identification flag, and judges which of “0” and “1” the identification flag is. The identification flag being “0” (step S 150 ) means that that the electronic money is cash-type, and therefore the control unit  302  ends the electronic money acquisition processing. 
     The identification flag being “1” (step S 150 ) means that the electronic money is signature-type, and therefore the control unit  302  makes a request to the mobile phone  200  for input of the first password (step S 151 ). 
     Next, the control-unit  206  receives the password request from the memory card  300  (step S 151 ), the display unit  208  displays a message to that effect, and the input unit  207  receives input of the first password (step S 152 ). The control unit  206  subjects the received first password to an encryption algorithm, thereby generating a first encrypted password (step S 153 ), and outputs the generated first encrypted password to the memory card  300  via the input/output unit  209  (step S 154 ). 
     Next, the control unit  302  receives the first encrypted password from the mobile phone  200  (step S 154 ), decrypts the received first encrypted password, thereby generating a first decrypted password (step S 155 ). The control unit  302  then extracts the identification flag, the electronic money ID and the amount from the received electronic money, concatenates the extracted identification flag, electronic money ID and amount, thereby generating a concatenated entity, and subjects the generated concatenated entity to an encryption algorithm E 1  with use of the generated first decrypted password, thereby generating a first authenticator (step S 156 ). Next, the control unit  302  overwrites the electronic money written in the information storage unit  304  such that the first authenticator therein is the generated first authenticator (step S 157 ). 
     (2) Operations for Using Electronic Money 
     The following describes operations for using electronic money in the electronic money usage system  10 , with reference to the flowchart shown in  FIG. 10  to  FIG. 12 . 
     The control unit  406  of the register apparatus  400  receives input of a sale amount from the operator of the register apparatus  400  (step S 201 ), and then receives detection information from the input/output unit  410  showing detection of mounting of the memory card  300  (step S 202 ). When the control unit  302  of the memory card  300  detects that the memory card  300  has been mounted in a register apparatus (step S 203 ), the authentication unit  402  and the authentication unit  303  perform mutual device authentication and key sharing (step S 204 ). 
     When the authentication unit  402  fails in device authentication (step S 205 ), the display unit  404  and the display unit  405  display a message to that effect (step S 206 ), and the control unit  406  ends the electronic money usage processing. 
     When the authentication unit  303  fails in device authentication (step S 207 ), the control unit  302  ends the electronic money usage processing. When the authentication unit  303  succeeds in device authentication (step S 207 ), the control unit  302  transmits notification of success to the register apparatus  400  (step S 208 ). 
     When the authentication by the authentication unit  402  succeeds (step S 205 ) and the control unit  406  receives a message showing failure from the memory card  300  (step S 209 ), the display unit  404  and the display unit  405  display a message to that effect (S 210 ), and the control unit  406  ends the electronic money usage processing. 
     When device authentication succeeds (step S 207 ), the control unit  302  reads the user ID  321  from the information storage unit  304  (step S 211 ), and outputs the read user ID to the register apparatus  400  (step S 212 ). 
     When the authentication by the authentication unit  402  succeeds (step S 205 ) and the message received from the memory card  300  shows success (step S 209 ), the control unit  406  receives the user ID from the memory card  300  (step S 212 ), and with use of the store private key  471  read from the key storage unit  401 , subjects the sale amount of which input was received to a digital signature, thereby generating sale amount signature data (step S 213 ). The control unit  406  then outputs the sale amount of which input was received and the generated sale amount signature data to the memory card  300  (step S 214 ). 
     Next, the control unit  302  receives the sale amount and the sale amount signature data from the register apparatus  400  (step S 214 ), and with use of the store public key  326  read from the information storage unit  304 , subjects the received sale amount and sale amount signature data to digital signature verification, and obtains a verification result (step S 215 ). When the verification result shows failure (step S 221 ), the control unit  302  outputs failure notification showing failure, to the register apparatus  400  (step S 222 ). When the control unit  406  receives the failure notification (step S 223 ), the display unit  404  and the display unit  405  display a message to that effect (step S 224 ), and the control unit  406  ends the electronic money usage processing. 
     When the verification result shows success (step S 221 ), the control unit  302  temporarily stores the received sale amount (step S 225 ), and searches the information storage unit  304  for electronic money that includes an amount the same as the amount shown by the sale amount (step S 226 ). When money that includes the same amount does not exist (step S 227 ), the control unit  302  outputs a search result to that effect to the register apparatus  400  (step S 228 ), and then ends the electronic money usage processing. When a search result is received showing that electronic money that includes the same amount does not exist (step S 229 ), the display unit  404  and the display unit  405  display a message to that effect (step S 230 ), and then the control unit  406  ends the electronic money usage processing. 
     When electronic money that includes the same amount exists (step S 227 ), the control unit  302  extracts the identification flag from that electronic money, and judges which of the “0” and “1” the extracted identification flag is. When the extracted identification flag is judged to be “0”, in other words when the electronic money is cash-type (step S 231 ), the control unit  302  moves the control to step S 247 . 
     When the extracted identification flag is “1”, in other words when the electronic money is signature-type (step S 231 ), the control unit  302  makes a request to the register apparatus  400  for input of a second password (step S 232 ). 
     When a search result is not received, or when the received search result shows that the electronic money exists (step S 229 ), the control unit  406  receives input of the second password from the memory card  300  (step S 232 ), the input/output unit  410  receives input of the second password, and the control unit  406  receives the second password from the input/output unit  410  (step S 233 ). The control unit  406  then encrypts the received second password, thereby generating a second encrypted password (step S 234 ), and outputs the generated second encrypted password to the memory card  300  (step S 235 ). 
     The control unit  302  receives the second encrypted password (step S 235 ), and decrypts the received second encrypted password, thereby generating a second decrypted password PW 2  (step S 236 ). The control unit  302  then bit concatenates, in the stated order, the identification flag, electronic money ID and amount extracted from the electronic money that includes the amount the same as the received sale amount, thereby generating a concatenated entity, and subjects the generated concatenated entity to an encryption algorithm E 1 , thereby generating a second authenticator. The control unit  302  overwrites the electronic money written in the information storage unit  304  such that the second authenticator therein is the generated second authenticator (step S 237 ). 
     Next, the control unit  302  extracts the first authenticator and the second authenticator from the electronic money (step S 241 ), and judges whether or not the extracted first authenticator and the extracted second authenticator match each other (step S 242 ). When the two are judged to not match (step S 242 ), the control unit  302  returns to step S 226  and repeats the processing. 
     When the two are judged to match (step S 242 ), the control unit  302  rewrites electronic money such that the identification flag is “0” (step S 243 ), the electronic money ID is “0x00” (step S 244 ), the first authenticator is “0x0000” (step S 245 ), and the second authenticator is “0x0000” (step S 246 ). Next, with use of the user private key  322  read from the information storage unit  304 , the control unit  302  subjects the electronic money whose identification flag, electronic money ID, first authenticator and second authenticator have been rewritten as above to a digital signature, thereby generating electronic money signature data (step S 247 ), and outputs the rewritten electronic money and the generated electronic money signature data to the register apparatus  400  (step S 248 ). 
     Next, the control unit  302  deletes the electronic money from the information storage unit  304  (step S 249 ). 
     The control unit  406  receives the electronic money and the electronic money signature data from the memory card  300  (step S 248 ), reads the piece of user information that includes the received user ID from the user information table  431 , extracts the user public key from the read piece of user information, and subjects the received electronic money and electronic money signature data to digital signature verification with use of the extracted user public key (step S 250 ). When verification fails (step S 251 ), the display unit  404  and the display unit  405  display a message to that effect (step S 254 ), and the control unit  406  ends the electronic money usage processing. 
     When verification is successful (step S 251 ), the control unit  406  writes the received electronic money to the information storage unit  409  (step S 252 ), and using the received electronic money, performs sale account settlement processing (step S 253 ). 
     1.7 Conclusion 
     As has been described, in the electronic money usage system  10 , the memory card  300  possessed by a user acquires signature-type or cash-type electronic money from the bank server apparatus  100  via the mobile phone  200 . When the acquired electronic money is cash-type, the memory card  300  internally stores the acquired electronic money as is. When the acquired electronic money is signature-type, the memory card  300  receives the first password from the user via the mobile phone  200 , generates a first authenticator with use of the first password and the identification flag, electronic money ID and amount included in the acquired electronic money, and writes the generated first authenticator in the electronic money. 
     When using the electronic money, the memory card  300  is mounted in the input/output unit  410  of the register apparatus  400 . 
     When using cash-type electronic money stored in the memory card  300 , the memory card  300  securely outputs the electronic money to the register apparatus  400 , and the register apparatus  400  performs account settlement using the received electronic money. 
     When the electronic money stored in the memory card  300  is signature-type, the memory card  300  receives the second password from the user via the input/output unit  410  of the register apparatus  400 , and using the second password and the identification flag, electronic money ID and amount included in the signature-type electronic money stored in the memory card  300 , generates a second authenticator, and writes the generated second authenticator in the electronic money. Next, the memory card  300  compares the first authenticator and the second authenticator included in the electronic money. If the two match, the memory card  300  converts the signature-type electronic money to the same format as the cash-type electronic money, securely outputs the cash-type electronic money generated as a result of the conversion to the register apparatus  400 , and the register apparatus  400  performs account settlement using the received electronic money. 
     In this way, when using the signature-type electronic money, the electronic money is output from the memory card  300  when, in the memory card  300 , the first authenticator generated using the first password input by the user when acquiring the signature-type electronic money and the second authenticator generated using the second password input by the user when using the electronic money. 
     Here, if the user at the time of acquiring the electronic value and the user at the time of using the electronic value are the same person, identical first data and second data will be able to be provided, and therefore the first authenticator and the second authenticator will of course match. 
     However, if the memory card storing the signature-type electronic money is lost or stolen, a person that attempts to dishonestly use the signature-type electronic money stored in the memory card does not know the first password. Consequently, if a second password that is different to the first password is input via the input/output unit  410  of the register apparatus  400 , the second authenticator that is generated as a result will not match the first authenticator generated using the first password, and therefore the memory card  300  does not output electronic money to the register apparatus  400 . 
     In this way, signature-type electronic money can be protected from dishonest use. 
     2. Modifications 
     The following describes an electronic money usage system  10   a  (not illustrated) as an example of a modification the above preferred embodiment. 
     As with the electronic money usage system  10 , the electronic money usage system  10   a  is composed of a bank server apparatus  100 , a mobile phone  200 , a memory card  300  and a register apparatus  400 . The bank server apparatus  100 , the mobile phone  200 , the memory card  300  and the register apparatus  400  are composed of the same structure as the bank server apparatus  100 , the mobile phone  200 , the memory card  300  and the register apparatus  400  of the electronic money usage system  10 . 
     The electronic money usage system  10   a  differs partly from the electronic money usage system  10  in terms of operations when acquiring electronic money. Furthermore, the electronic money usage system  10   a  differs partly to the electronic money usage system  10  in terms of operations when using electronic money. The following description focuses on these differences. 
     When acquiring electronic money in the electronic money usage system  10   a , the same operations as steps S 101  to s 157  in  FIGS. 7 to 9  are performed, but with a difference in the following step. 
     In step S 156 , the control unit  302  uses a digital signature algorithm S 1  instead of the encryption algorithm E 1 . Here, as one example, the digital signature algorithm S 1  is an elliptic curve ElGamal signature algorithm. 
     In other words, the control unit  302  extracts the identification flag, the electronic money ID and the amount from the received electronic money, and bit concatenates the extracted identification flag, electronic money ID and amount in the stated order, to generate a concatenated entity. The operations are the same as in the electronic money usage system  10  up to this point. Next, the control unit  302  subjects the first decrypted password to a hash function SHA-1, to generate a private key SK 1 . 
     SK 1 =SHA-1 (first decrypted password) 
     Since the hash function SHA-1 is commonly known, a description thereof is omitted here. 
     Next, the control unit  302  subjects the generated concatenated entity to the digital signature algorithm S 1 , using the generated private key SK 1  as a key, to generate a first authenticator Sign 1 . 
     Sign 1 =S 1  (SK 1 , identification flag∥electronic money ID∥amount) 
     When using electronic money in the electronic money usage system  10   a , the same operations as steps S 201  to s 253  in  FIGS. 10 to 12  are performed, but with a difference in the following step. 
     At step S 237 , the control unit  302  uses the digital signature algorithm S 1  instead of the encryption algorithm E 1 . 
     In other words, the control unit  302  extracts the identification flag, the electronic money ID and the amount from the electronic money that includes the same amount as the received sale amount, and bit concatenates the extracted identification flag, electronic money ID and amount in the stated order, to generate a concatenated entity. The operations are the same as in the electronic money usage system  10  up to this point. Next, the control unit  302  subjects the second decrypted password to a hash function SHA-1, to generate a private key SK 2 . 
     SK 2 =SHA-1 (second decrypted password) 
     Next, the control unit  302  subjects the generated concatenated entity to the digital signature algorithm S 1 , using the generated private key SK 2  as a key, to generate a second authenticator Sign 2 . 
     Sign 2 =S 1  (SK 2 , identification flag∥electronic money ID∥amount) 
     Next, the control unit  302  generates a public key PK from the generated private key SK 2 . Note that one example of the generation method for the public key is commonly known in elliptical curve ElGamal signature, and therefore a description thereof is omitted. 
     Furthermore, in the operations when using electronic money in the electronic money usage system  10   a , after the operations at step S 237  have finished, the operations shown in the flowchart in  FIG. 13  are performed instead of the operations at steps S 241  to S 253  in the flowchart shown in  FIG. 12 . 
     The control unit  302  of the memory card  300  generates electronic money signature data in the same way as in step S 247  (step S 301 ), and outputs the generated public key PK, the electronic money, and the generated electronic money signature data to the register apparatus  400  via the input/output unit  301  (step S 302 ). 
     The control unit  406  of the register apparatus  400  receives the public key PK, the electronic money and the electronic money signature data via the input/output unit  410  from the memory card  300  (step S 302 ), and performs verification of the electronic money signature data in the same way as step S 250  (step S 303 ). When verification fails (step S 304 ), the control unit  406  instructs the display unit  404  and the display unit  405  to display a message to that effect, and the display unit  404  and the display unit  405  display the message (step S 305 ). The electronic money usage processing then ends. 
     When verification succeeds (step S 304 ), the control unit  406  reads the first authenticator and the second authenticator from the received electronic money (step S 306 ), and then judges whether or not the read first authenticator and second authenticator match each other. When the two are judged not to match (step S 307 ), the control unit  406  instructs the display unit  404  and the display unit  405  to display a message to that effect, and the display unit  404  and the display unit  405  display the message (step S 308 ). The control unit  406  then ends the electronic money usage processing. 
     When the two are judged to match (step S 307 ), the control unit  406  extracts the identification flag, the electronic money ID and the amount from the received electronic money, and concatenates the identification flag, the electronic money ID and the amount in the stated order, to generate a concatenated entity. The control unit  406  then uses the received public key PK to subject the generated concatenated entity and the read first authenticator to a digital signature (step S 309 ). When the result of verification is failure (step S 310 ), the control unit  406  instructs the display unit  404  and the display unit  405  to display a message to that extent, and the display unit  404  and the display unit  405  display the message (step S 311 ). The control unit  406  then ends the electronic money usage processing. 
     When the result of verification is success (step S 310 ), the control unit  406  stores the electronic money in the same way as at step S 252  (step S 312 ), and performs account settlement processing in the same way as at step S 253  (step S 313 ). Next, the control unit  406  outputs success notification that shows that the verification result is success (step S 314 ), and the control unit  302  deletes the stored electronic money from the information storage unit  304  (step S 315 ). 
     (Conclusion of Modification) 
     As has been described, in the electronic money usage system  10   a , the memory card  300  possessed by the user acquires signature-type or cash-type electronic money from the bank server apparatus  100  via the mobile phone  200 . When the acquired electronic money is cash-type, it is stored in the memory card  300  as is. When the acquired electronic money is signature-type, the memory card  300  receives the first password from the user via the mobile phone  200 , and uses the first password and the identification flag, the electronic money ID and the amount included in the acquired electronic money to generate the first authenticator, and writes the generated first authenticator in the electronic money. 
     When using the electronic money, the memory card  300  is mounted in the input/output unit  410  of the register apparatus  400 . 
     When the electronic money stored in the memory card  300  is cash-type, the memory card  300  securely outputs the electronic money to the register apparatus  400 , and the register apparatus performs account settlement with the received electronic money. 
     When the electronic money stored in the memory card  300  is signature-type, the memory card  300  receives the second password from the user via the input/output unit  410  of the register apparatus  400 , uses the second password and the identification flag, the electronic money ID and the amount included in the signature-type electronic money stored in the memory card  300  to generate the second authenticator, and writes the generated second authenticator in the electronic money. 
     Next, the memory card  300  securely outputs the signature-type electronic money that includes the first authenticator and the second authenticator to the register apparatus  400 , and the register apparatus  400  receives the signature-type electronic money. 
     Next, the register apparatus  400  extracts the first authenticator and the second authenticator from the received electronic money, and compares the extracted first authenticator and second authenticator. If the two match, the register apparatus  400  treats the received signature-type electronic money as legitimate, and performs account settlement using the received electronic money. 
     In this way, the register apparatus  400  judges whether or not the first authenticator generated using the first password input by the user when acquiring the signature-type electronic money matches the second authenticator generated using the second password input by the user when using the signature-type electronic money, and when the two match, the electronic money is treated as being legitimate. 
     As with the electronic money usage system  10 , if the user at the time of acquiring the electronic value and the user at the time of using the electronic value are the same person, identical first data and second data will be able to be provided, and therefore the first authenticator and the second authenticator will of course match. 
     However, if the memory card storing the signature-type electronic money is lost or stolen, a person that attempts to dishonestly use the signature-type electronic money stored in the memory card does not know the first password. Consequently, if a second password that is different to the first password is input via the input/output unit  410  of the register apparatus  400 , the second authenticator that is generated as a result will not match the first authenticator generated using the first password, and therefore the register apparatus  400  does not treat the received electronic money as legitimate. 
     In this way, signature-type electronic money can be protected from dishonest usage. 
     3. Other Modifications 
     Although the present invention has been described based on the above preferred embodiment, the present invention is not limited to the preferred embodiment and modifications thereof. Cases such as the following are included in the present invention. 
     (1) In the preferred embodiment, electronic money is described as being stored in the memory card  300  which is a portable medium. However, the mobile phone may include therein a structure the same as the memory card  300 . In other words, the same structure as the memory card  300  may be included in the mobile phone such that it is not removable from the mobile phone. 
     In such a case, the mobile phone and the register apparatus  400  each include a short-distance radio communication unit, and communicate via these short-distance radio communication units using a method such as a short-distance radio communication method. 
     Instead of the mobile phone  200 , the electronic money usage system  10  may include a mobile information terminal apparatus that includes the same structure as the mobile phone  200 . 
     The memory card  300  may further include a short-distance radio communication unit, and the register apparatus  400  may further include a short-distance radio communication unit, and the memory card  300  and the register apparatus  400  may communicate with each other via these short-distance radio communication units using a method such as a short-distance radio communication method. The memory card  300  may remain mounted in the mobile phone apparatus  200  when the short-distance radio communication takes place. 
     (2) In the preferred embodiment, the user selects and acquires either cash-type electronic money or signature-type electronic money. However, the present invention may have a structure such that only signature-type electronic money can be acquired. 
     (3) The preferred embodiment and modifications may be structured in the following way. 
     The banks server  100  and the register apparatus may be connected via the Internet  20  and have a safe communication path. 
     As shown in  FIG. 2 , the information storage unit  102  of the bank server apparatus  100  stores the issued electronic money table  151 . When the reissue section in a piece of issue information in the issued electronic money tale  151  is “0”, the bank server apparatus  100  generates new electronic money in response to a request from the user. The request from the user when, for instance, he/she has lost the memory card  300 . The bank server apparatus  100  transmits the generated electronic money to the memory card via the mobile phone  200 . At this time, the bank server apparatus  100  sets the reissue section included in the piece of issue information to “1”. The bank server apparatus  100  also generates a piece of issue information corresponding to the newly generated electronic money, and adds the generated piece of issue information to the issued electronic money table  151 . 
     When the reissue section in a piece of issue information in the issued electronic money table  151  is “1”, the bank server apparatus  100  does not newly generate electronic money in response to a request from a user. 
     Furthermore, when the second authenticator is generated at the time of using the signature-type electronic money stored in the memory card  300 , the memory card  300  transmits usage information showing that the electronic money is used, to the bank server apparatus  100  via the register apparatus  400 . Included in this usage information includes the user ID that identifies the user of the memory card  300 , and the electronic money ID included in the electronic money. 
     On receiving the usage information that includes the user ID and the electronic money ID, the bank server apparatus  100  extracts the piece of issue information that includes the received user ID and electronic money ID from the issued electronic money table  151 . The bank server apparatus  100  writes the reissue section in the extracted piece of issue information to “1”, and then overwrites the piece of issue information in the issued electronic money table  151  with the piece of issue information that has the updated reissue section. In this case, since the reissue section is “1”, new electronic money will not be issued. 
     Note that in the case of the above (1), a mobile phone that includes therein the same structure as the memory card  300  may transmit the user information to the bank server apparatus  100 . 
     (4) The above preferred embodiment and modifications are based on the assumption that the whole of the amount included in the electronic money is used when signature-type electronic money is used. An example of this is when a 10,000 yen purchase is made, electronic money equivalent in value to 10,000 yen of currency is used. However, is it possible to use only part of the amount included in the electronic money. For instance, when making a 1,000 purchase, electronic money equivalent in value to 10,000 yen may be used for the 1,000 purchase, with only 1,000 yen of the 10,000 yen amount of the electronic money actually being used, and the balance 9,000 yen remaining as electronic money. 
     Operations for using electronic money in the electronic money usage system  10  in this case are described with use of the flowchart shown in  FIG. 14  and  FIG. 15 . Note that operations for acquiring electronic money are the same as in the electronic money usage system  10 . 
     The information storage unit  304  of the memory card  300  stores electronic money  511  shown in  FIG. 16A . This electronic money  511  is used in the following. As shown in  FIG. 16A , the electronic money  511  is composed of an identification flag “1”, an electronic money ID “0x0F”, an amount “10000”, a first authenticator “E 1  (PW 1 ,1∥0x0F∥10000)”, and a second authenticator “blank”. 
     The control unit  406  of the register apparatus  400  receives a sale amount (usage amount) from the operator of the register apparatus  400  (step S 321 ), and outputs the usage amount to the memory card  300  via the input/output unit  410  (step S 322 ). 
     The control unit  302  receives the usage amount from the register apparatus  400  via the input/output unit  301  (step S 322 ), and compares the received usage amount and the amount (balance) of the electronic money  511  stored in the information storage unit  304 . If the usage amount and the balance match (step S 323 ), subsequent processing is the same as in the electronic money usage system  10  (step S 327 ). 
     When the usage amount is greater than the balance (step S 323 ), the control unit  302  outputs insufficiency information showing that the amount is insufficient, to the register apparatus  400  via the input/output unit  301  (step S 324 ). The control unit  302  then ends the electronic money usage processing. When the received information is insufficiency information (step S 325 ), the control unit  406  outputs a message to that effect to the display unit  404  and the display unit  405 , and the display unit  404  and the display unit  405  display the message (step S 326 ). The control unit  406  then ends the electronic money usage processing. 
     When the usage amount is less than the balance (step S 323 ), the control unit  302  outputs a password request to the register apparatus  400  via the input/output unit  301  (step S 328 ). The input/output unit  410  receives input of the second password from the user, under the control of the control unit  406  (step S 329 ), and the control unit  406  securely outputs the second password to the memory card (step S 330 ). The control unit  302  receives the second password (step S 330 ), generates a second authenticator in the same way as at step S 237  using the received second password (step S 331 ), and compares the first authenticator and the second authenticator in the same way as at step S 242 . If the first authenticator and the second authenticator do not match (step S 332 ), the control unit  302  transmits non-match information showing that the two authenticators do not match, to the register apparatus  400  (step S 333 ). If the received information is non-match information showing that the two authenticators do not match (step S 334 ), the control unit  406  outputs a message to that effect to the display unit  404  and the display unit  405 , and the display unit  404  and the display unit  405  display the message (step S 335 ). The control unit  406  then ends the electronic money usage processing. 
     If the first authenticator and the second authenticator match (step S 332 ), the control unit  302  updates the electronic money (step S 351 ). 
     Details of the updating of the electronic money are as follows. 
     The control unit  302  subtracts the usage amount from the amount included in the electronic money  511 , and overwrites the amount with the result (step S 352 ). The control unit  302  then extracts the identification flag, the electronic money ID and the amount from the electronic money, and concatenates these in the stated order, to generate a concatenated entity. The control unit  302  then subjects the generated concatenated entity to the encryption algorithm E 1  using the received second password, and overwrites the electronic money such that the first authenticator stored therein is the generated first authenticator. 
     First authenticator Sign 1 =E 1 (second password PW 2 , identification flag∥electronic money ID∥amount) (step S 353 ). 
     Here, as shown in  FIG. 16B , the electronic money is electronic money  512 , and is composed of an identification flag “1”, an electronic money ID “0x0F”, an amount “9000”, a first authenticator “E 1  (PW 2 ,1 ∥0x0F∥9000)”, and a second authenticator “blank”. 
     Next, the control unit  302  generates new electronic money (step S 354 ). 
     Details of the generating of the electronic money are as follows. 
     The control unit  302  sets the identification flag “0” (step S 355 ), sets the electronic money ID to have the same value as the original electronic money ID (step S 356 ), sets the amount to be equivalent to the usage amount (step S 357 ), sets the first authenticator to “0x0000” (step S 358 ), and sets the second authenticator to “0x0000” (step S 359 ). 
     As shown in  FIG. 16C , the new electronic money is electronic money  513 , and is composed of an identification flag “0”, an electronic money ID “0x00”, an amount “1000”, a first authenticator “0x0000”, and a second authenticator “0x0000”. 
     Next, the control unit  302  securely outputs the generated new electronic money to the register apparatus  400  via the input/output unit  301  (step S 360 ). 
     The control unit  406  receives the new electronic money from the memory card  300  (step S 360 ), stores the received new electronic money internally (step S 361 ), then performs account settlement processing using the received new electronic money (step S 362 ). 
     (5) In the preferred embodiment and modifications, a single piece of electronic money includes a single amount. However, a single piece of electronic money may include a plurality of amounts. The amounts may be used one at a time, and each time one of the amounts is used, that used amount is deleted from the electronic money. 
     An example of this electronic money is shown in  FIG. 17 . 
     Electronic money  521  shown in  FIG. 17  is composed of a header  531 , and amount sections  532 ,  533 , . . .  534 . 
     The header  531  includes an identification flag and an electronic money ID. The identification flag and the electronic money ID are as already described. 
     Each amount section includes an amount, a first authenticator and a second authenticator. The amount, first authenticator and second authenticator are as already described. 
     The bank server apparatus  100  outputs the electronic money  521  to the memory card  300 . Note that the first and second authenticators in each amount section in the electronic money  521  are blank at this point. 
     Upon receiving the electronic money  521 , the memory card  300  generates the first authenticator for each amount section, and overwrites each amount section so as to include the generated first authenticator. 
     When using any of the amount sections in the electronic money, the memory card  300  generates a second authenticator, compares the first authenticator and the second authenticator, and when the two match, generates cash-type electronic money composed of the header and the particular amount section. Here, the first and second authenticators in the particular amount section are “0x0000”. Next, the memory card  300  outputs the generated cash-type electronic money to the register apparatus  400 . The memory card  300  deletes the particular amount section from the electronic money  521 . 
     The register apparatus  400  receives the cash-type electronic money, and performs account settlement processing using the received electronic money. 
     (6) In the electronic money usage system  10 , the first authenticator and the second authenticator included in the electronic money may be generated using another encryption algorithm or another public key encryption digital signature. Furthermore, the first authenticator and the second authenticator may be generated using another digital signature. Alternatively, the first authenticator and the second authenticator may be generated using another operation, examples of which include a exclusive OR and a hash function. 
     (7) In the electronic money usage system  10 , the electronic money output from the memory card  300  to the register apparatus  400  may have a data structure that does not include an identification flag and an electronic money ID. In other words, the electronic money may include only an amount. 
     (8) In the electronic money system  10   a , the memory card  300  may store a user&#39;s first stored password therein in advance, and when acquiring the electronic money, the memory card  300  may make a request to the user, via the mobile phone  200 , to input a first input password. Having received the first input password, the memory card  300  may judge whether or not the first stored password and the first input password match, and when the two are judged not to match, refuse electronic money acquisition. On the other hand, when the two are judged to match, the memory card  300  may permit electronic money acquisition. 
     Here, the memory card  300  stores a memory card private key in secret, and the register apparatus  400  stores a memory card public key generated corresponding to the memory card private key. When the aforementioned passwords are judged to match, the memory card  300  subjects a concatenated entity of the identification flag, the electronic money ID and the amount included in the received electronic money to a digital signature using the memory card private key, thereby generating a first authenticator. The memory card  300  then writes the generated first authenticator in the electronic money. 
     The register apparatus  400  stores the user&#39;s second stored password therein, and when the electronic money is being used, the register apparatus  400  makes a request to the user to input a second input password, receives the second input password, judges whether or not the second stored password and the second input password match, and when the two do not match, refuses electronic money usage. 
     On the other hand, when the two are judged to match, the register apparatus  400  receives the electronic money from the memory card  300 , extracts the first authenticator from the received electronic money, and subjects the electronic money and the first authenticator to digital signature verification using the stored memory card public key. The register apparatus  400  refuses electronic money usage when the verification result is failure, and permits electronic money usage when the verification result is success. 
     (9) In the preferred embodiment and modifications, instead of the user inputting a password, biometric information of the user may be used. For instance, the user&#39;s fingerprint information or iris information may be used. 
     (10) The preferred embodiment and modifications use an example that in the case of the electronic money being signature-type, the first authenticator and the second authenticator are authentication-use data generated based on the password input by the user and the identification flag, electronic money ID and amount included in the electronic money (see  FIGS. 3A and 3B ). 
     However, the present invention is not limited to this structure. The first authenticator and the second authenticator may be the input password itself. 
     (11) In the preferred embodiment, the control unit  302  of the memory card  300  bit concatenates, in the stated order, the identification flag, electronic money ID and amount extracted from the electronic money that includes the same amount as the received sale amount, to generate a concatenated entity; subjects the generated concatenated entity to the encryption algorithm E 1  using the generated second decrypted password PW 2 , thereby generating a second authenticator; overwrites the second authenticator in the electronic money in the information storage unit  304  with the generated second authenticator; extracts the first authenticator and the second authenticator from the electronic money; and judges whether or not the extracted first authenticator and the extracted second authenticator match. However, instead of overwriting the electronic money to include the generated second authenticator, the control unit  302  may compare the generated second authenticator with the extracted first authenticator directly after generating the second authenticator. 
     (12) In the preferred embodiment and modifications, electronic money is used in place of currency, but the present invention is not limited to this structure. Instead of electronic money, electronic value information such as electronic coupons, bonus points, frequent flier points or the like may be used. 
     (13) Each described apparatus is, specifically, a computer system composed of a microprocessor, a ROM, a RAM, and the like. Computer programs are stored in the RAM. The computer program is composed of a plurality of instruction codes showing instructions with respect to a computer in order to have predetermined functions achieved. Each apparatus achieves predetermined functions by the microprocessor operating according to the computer programs. In other words, the microprocessor reads one of the instructions included in the computer program at a time, decodes the read instruction, and operates in accordance with the result of the decoding. 
     (14) All or part of the compositional elements of each apparatus may be composed of one system LSI (Large Scale Integrated circuit). The system LSI is a super-multifunctional LSI on which a plurality of compositional units are manufactured integrated on one chip, and is specifically a computer system that includes a microprocessor, a ROM, a RAM, or the like. Computer programs are stored in the RAM. The system LSI achieves its functions by the microprocessor operating according to the computer programs. 
     Furthermore, the units that are the compositional elements of each of the apparatuses may be realized separately with individual chips, or part or all may be included on one chip. Here, the LSI may be an IC, a system LSI, a super LSI, or ultra LSI, depending on the degree of integration. 
     Furthermore, the integration of circuits is not limited to being realized with LSI, but may be realized with a special-purpose circuit or a general-use processor. Alternatively, the integration may be realized with use of a FPGA (field programmable gate array) that is programmable after manufacturing of the LSI, or a re-configurable processor that enables re-configuration of the connection and settings of circuit cells in the LSI. 
     (15) Part or all of the compositional elements of each apparatus may be composed of a removable IC card or a single module. The IC card or the module is a computer system composed of a microprocessor, a ROM, a RAM, and the like. The IC card or the module may be included in the aforementioned super-multifunctional LSI. The IC card or the module achieves its functions by the microprocessor operating according to computer programs. The IC card or the module may be tamper-resistant. 
     (16) The present invention may be methods shown by the above. Furthermore, the methods may be a computer program realized by a computer, and may be a digital signal of the computer program. 
     Furthermore, the present invention may be a computer-readable recording medium such as a flexible disk, a hard disk, a CD-ROM, an MO, a DVD, a DVD-ROM, a DVD-RAM, a BD (Blu-ray Disc) or a semiconductor memory, that stores the computer program or the digital signal. Furthermore, the present invention may be the computer program or the digital signal recorded on any of the aforementioned recording media. 
     Furthermore, the present invention may be the computer program or the digital signal transmitted on a electric communication network, a wireless or wired communication network, a network of which the Internet is representative, or a data broadcast. 
     Furthermore, the present invention may be a computer system that includes a microprocessor and a memory, the memory storing the computer program, and the microprocessor operating according to the computer program. 
     Furthermore, by transferring the program or the digital signal to the recording medium, or by transferring the program or the digital signal via a network or the like, the program or the digital signal may be executed by another independent computer system. 
     (17) The present invention may be any combination of the above-described embodiment and modifications. 
     INDUSTRIAL APPLICABILITY 
     The apparatuses, recording medium and electronic value of the present invention can be used for managerially, in other words, repeatedly and continuously, in general industries in which general transactions are performed. Furthermore, the apparatuses and recording medium of the present invention can be manufactured and sold managerially, in other words, repeatedly and continuously, in an electronic device manufacturing industry.