Abstract:
A method of setting validity period of IC card, includes preparing IC card including change unit whose state changes with lapse of time starting from initial state without external power, measuring unit configured to measure state of change unit so as to generate information indicating whether or not validity period has elapsed, and operation unit configured to be operable if information indicates that validity period fails to have yet elapsed, and to be inoperable if information indicates that validity period has elapsed, preparing IC card case capable to house IC card by user, IC card case including identification unit configured to determine whether or not user is legitimate, performing user identification utilizing identification unit, when IC card is housed in IC card case, and transmitting signal to change unit in IC card depending on result of user identification, signal initializing change unit to initial state.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a divisional of and claims the benefit of priority from U.S. Ser. No. 10/720,100, filed Nov. 25, 2003, and is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2003-023220, filed Jan. 31, 2003, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an IC card and an IC card case devised to prevent illegal use and battery charger for supplying power to the IC card case.  
         [0004]     2. Description of the Related Art  
         [0005]     Integrated circuit (IC) cards have come to be used in various fields as employee ID cards, club member ID cards, insurance ID cards, etc., in addition to business transaction cards, such as credit cards and debit cards. Since IC cards are equipped with a CPU, ROM, RAM, EEPROM, etc., which are not incorporated in conventional magnetic cards, they can have various functions and are hard to forge, which significantly enhances their security. Therefore, IC cards are often used to store personal information (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2001-312711).  
         [0006]     Attention has recently been paid to power analysis attacks against IC cards. In these attacks, the key used in an encryption scheme, such as DES and RSA, which is often utilized when IC cards are identified by a card reader, is found by analyzing the power consumed while the decryption algorithm is being executed. Such methods as the above for attacking IC cards without opening the cards have greatly advanced.  
         [0007]     As described above, IC cards are hard to forge and hence have come to be widely used to store personal information, while IC card attacking methods have greatly advanced. Therefore, if an IC card is lost and acquired by a third party, it can be used illegally, resulting in serious damage.  
         [0008]     As a countermeasure to cope with, for example, an IC card being lost and acquired by a third party, the amount of money that can be transacted in a single month is limited, or the number of occasions the card can be used is limited. However, this is not a fundamental solution for preventing illegal use when an IC card is lost. As another countermeasure, some IC cards have a built-in timer for limiting the period of the validity of the card. In this case, however, a power supply must be incorporated in the card to allow the timer to operate continuously, which is a serious problem for IC cards, as their specifications are limited.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009]     The preset invention has been developed in light of the above, and aims to provide an IC card and IC card case that can prevent their illegal use without a power supply, even if they are lost, simply by changing the data stored in the card and/or the structure of the card.  
         [0010]     According to a first aspect of the invention, there is provided a method of setting a validity period of an IC card, comprising: preparing an IC card including a change unit whose state changes with lapse of time starting from an initial state without an external power, a measuring unit configured to measure the state of the change unit so as to generate information indicating whether or not the validity period has elapsed, and an operation unit configured to be operable if the information indicates that the validity period fails to have yet elapsed, and to be inoperable if the information indicates that the validity period has elapsed; preparing an IC card case capable to house the IC card by a user, the IC card case including an identification unit configured to determine whether or not the user is legitimate; performing user identification utilizing the identification unit, when the IC card is housed in the IC card case; and transmitting a signal to the change unit in the IC card depending on a result of the user identification, the signal initializing the change unit to the initial state.  
         [0011]     According to a second aspect of the invention, there is provided an IC card unusing a built-in power supply and driven by an external power supplied from an external device when the IC card is connected to the external device, the IC card comprising: a change unit whose state changes with lapse of time starting from an initial state without the external power; a measuring unit configured to measure the state of the change unit so as to generate information indicating whether or not a period has elapsed; and an operation unit configured to be operable if the information indicates that the period fails to have yet elapsed, and to be inoperable if the information indicates that the period has elapsed.  
         [0012]     According to a third aspect of the invention, there is provided an IC card case capable to house an IC card by a user, the IC card starting measurement of a period in response to an instruction and continuing the measurement without an external power, the IC card being usable if the period fails to have elapsed and being unusable if the period has elapsed, the IC card case comprising: an identification unit configured to determine whether or not the user is legitimate; a performing unit configured to perform user identification utilizing the identification unit, when the IC card is housed in the IC card case; and a transmission unit configured to transmit a signal to the IC card depending on a result of the user identification, the signal initializing the IC card to the initial state.  
         [0013]     According to a fourth aspect of the invention, there is provided a charger to be connected to an IC card case to charge a battery unit provided in the IC card case capable to house an IC card by a user, the battery unit being configured to issue an instruction to the IC card, the IC card starting measurement of a period in response to the instruction, and continuing the measurement without an external power, the IC card being usable if the period fails to have elapsed and being unusable if the period has elapsed, the charger comprising: a determination unit configured to determine whether or not the IC card case is a preset IC card case, when the IC card case is connected to the charger; and a charging unit configured to charge the battery unit if the determination unit determines that the IC card case is the preset IC card case. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0014]      FIG. 1  illustrates the whole system according to an embodiment of the invention;  
         [0015]      FIG. 2  is a block diagram illustrating the configuration of an IC card reader  1  used in the embodiment;  
         [0016]      FIG. 3  is a block diagram illustrating the configuration of an IC card  2  used in the embodiment;  
         [0017]      FIG. 4  is a block diagram illustrating the basic concept of an aging device  37 ;  
         [0018]      FIG. 5  is a block diagram illustrating a first example for realizing the aging device  37 ;  
         [0019]      FIG. 6  illustrates changes in the state of an aging device  37 - 1  with lapse of time;  
         [0020]      FIG. 7  is a graph illustrating the relationship between the time and the output signal of the aging device  37 - 1 ;  
         [0021]      FIG. 8  is a block diagram illustrating a second example for realizing the aging device  37 ;  
         [0022]      FIG. 9  is a block diagram illustrating a third example for realizing the aging device  37 ;  
         [0023]      FIG. 10  is a block diagram illustrating the structure of the aging device  37 ;  
         [0024]      FIG. 11  is a block diagram illustrating another example of the aging device  37 ;  
         [0025]      FIG. 12  is a block diagram illustrating an IC card case  3  used in the embodiment;  
         [0026]      FIG. 13  is a flowchart useful in explaining the operation of housing the IC card  2  into the IC card case  3 ;  
         [0027]      FIG. 14  is a flowchart useful in explaining the operation of ejecting the IC card  2  from the IC card case  3  to use it;  
         [0028]      FIG. 15  is a flowchart useful in explaining the operation of permitting a user to use the IC card  2 ; and  
         [0029]      FIG. 16  is a block diagram illustrating a charger  6 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0030]     An embodiment of the invention will be described in detail with reference to the accompanying drawings.  
         [0031]      FIG. 1  illustrates the whole system according to the embodiment.  
         [0032]     In this system, an IC card service provider provides services through an IC card  2 . The owner of the IC card  2 , who can utilize the services, stores it in an IC card case  3  when the owner does not utilize the services. On the other hand, to utilize the services, the owner takes the card  2  out of the card case  3  and inserts it into an IC card reader  1  owned by the IC card service provider.  
         [0033]     A database  4  stores and manages data concerning IC card owners who utilize the services, in a centralized manner. In the embodiment, the database  4  stores at least an ID and cipher key assigned to each IC card  2 , in relation to each other.  
         [0034]     A large number of IC card readers  1  are provided by the IC card service provider, and connected to the database  4  via a network  5 . In the case of the services that are provided only at a particular place, it is a matter of course that the IC card reader  1  may store the database  4  and the network  5  may not be used.  
         [0035]      FIG. 2  is a block diagram illustrating the configuration of the IC card reader  1 .  
         [0036]     In  FIG. 2 , a contact unit  21  is an interface that is electrically connected to the IC card  2  when the IC card  2  is inserted in the IC card reader  1 , and exchanges data with the IC card  2 . An input unit  22  is used when the owner of the IC card  2  inputs a password or any other data. A power supply unit  23  supplies power to the IC card  2  via the contact unit  21  when the IC card  2  is inserted.  
         [0037]     A password identification unit  24  reads a password from the IC card  2  via the contact unit  21 , thereby determining whether or not the read password is identical to that input from the input unit  22 , to confirm the legitimacy of the user. If they are determined to be identical, an allowance signal is output to a cipher key acquisition unit  25 .  
         [0038]     Upon receiving the allowance signal from the password identification unit  24 , the cipher key acquisition unit  25  reads an ID from the IC card  2  via the contact unit  21 , thereby issuing a request to the database  4  via a communication unit  26 , using the ID, and acquiring therefrom the cipher key uniquely corresponding to the ID.  
         [0039]     A card identification unit  27  utilizes the cipher key acquired by the cipher key acquisition unit  25 , to confirm the legitimacy of the inserted IC card  2 . This identification process will be described later.  
         [0040]     A power supply  28  is supplied with an external AC power supply and supplies power to the each internal element of the IC card reader  1 . The power supply unit  23  is also supplied with power from the power supply  28 .  
         [0041]     An IC card owner who utilizes IC card services carries the IC card  2 , and inserts the card  2  into the IC card reader  1  when the IC card owner utilizes the services.  
         [0042]      FIG. 3  is a block diagram illustrating the configuration of the IC card  2 .  
         [0043]     In  FIG. 3 , a contact unit  31  is exposed on the outer surface of the IC card  2  so that it is electrically connected to the contact unit  21  of the IC card reader  1  when the IC card  2  is inserted in the IC card reader  1 . When the IC card  2  is inserted in the IC card reader  1 , power is supplied from the power supply unit  23  of the IC card reader  1  to the power supply unit  38  of the IC card  2  via the contact unit  31 . The power supply unit  38  supplies each element in the IC card  2 .  
         [0044]     A process unit  32  performs various procedures while services are being utilized in the IC card  2 .  
         [0045]     A password storage  33  stores a password for using the IC card  2 . In general, passwords are stored in IC cards  2  when the cards  2  are distributed to users. An ID storage  34  stores an ID from which the IC card  2  is identified. In general, IDs are stored in IC cards  2  when the cards  2  are manufactured. A cipher key storage  35  stores a cipher key assigned to the IC card  2 . Generally, cipher keys are stored in IC cards  2  when the cards  2  are distributed to users.  
         [0046]     A card identification unit  36  cooperates with the card identification unit  27  to determine whether or not the IC card  2  is used by a legitimate user, when the IC card  2  is inserted in the IC card reader  1 .  
         [0047]     An aging device  37  can determine whether or not a predetermined time period has elapsed. When the aging device  37  operates, it is not necessary to supply power thereto. When the aging device  37  is supplied with power (device charging power) via the contact unit  31  from the IC card case  3  described later, it starts time measurement. The aging device  37  is referred to by the card identification unit  36 , when the IC card  2  is connected to the IC card reader  1  and the card identification unit  36  performs identification.  
         [0048]     The aging device  37  will now be described in detail.  
         [0049]      FIG. 4  is a block diagram illustrating the basic concept of the aging device  37 . The aging device  37  comprises a change unit  41 , the state of which changes with lapse of time without a power supply, such as battery; an input unit  42  for inputting an input signal to the change unit  41 ; and an output unit  43  for outputting an output signal changed relative to the input signal based on the state of the change unit  41 . The change in the state of the change unit  41  is utilized to measure time. The input unit  42  and output unit  43  are used to confirm the state of the change unit  41 .  
         [0050]      FIG. 5  is a block diagram illustrating a first example for realizing the aging device  37  of  FIG. 4 .  
         [0051]     The aging device  37 - 1  comprises: a first layer having a source region  51 , drain region  52  and channel region  53  therebetween; a second layer provided on the first layer and formed of a tunnel insulation film  54 ; a third layer provided on the second layer and formed of a floating gate  55 ; a fourth layer provided on the third layer and formed of an insulation film  56 ; and a fifth layer provided on the fourth layer and formed of a control gate  57 . A source electrode  58  and drain electrode  59  are provided on the source and drain regions  51  and  52 , respectively.  
         [0052]      FIG. 6  illustrates changes with lapse of time in the state of the aging device  37 - 1  of  FIG. 5 . In the figure, hatched circles indicate electrons, and white circles indicate positive holes.  
         [0053]     In  FIG. 6 , state  1  is the initial state. In the aging device  37 - 1  that assumes the state  1 , a pre-process is performed, in which the control gate  57  applies a high electric field between the substrate boundary of the channel region  53  and the floating gate  55 , thereby injecting electrons from the channel into the floating gate  55  utilizing FN tunneling. At this time, positive holes gather at the substrate boundary of the channel region  53 , whereby a channel is defined at the substrate boundary between the source and drain regions  51  and  52 .  
         [0054]     In the state  1 , the electrons in the floating gate  55  gradually shift, by direct tunneling, to the substrate boundary, thereby reducing the level of the electric field at the substrate boundary in the channel region  53 . State  2  of  FIG. 6  is the state assumed at a time point T 1  a certain time period after the state  1 . State  3  of  FIG. 6  is the state assumed at a time point T 2  a certain time period after the state  2 . Similarly, state  4  is the state assumed at a time point T 3  a certain time period after the state  3 . The circles indicated by the broken lines represent the shift of electrons made due to direct tunneling by the respective time points. In the state  4  at the time point T 3 , most electrons escape from the floating gate  55 , therefore the channel at the substrate boundary of the channel region  53  disappears. As a result, no signals are output.  
         [0055]      FIG. 7  is a graph illustrating the relationship between the time and the output signal of the aging device  37 - 1 . Direct tunneling occurs between time points T a (=0) and T b , and lastly, the channel disappears, whereby the level of the output signal is reduced to the noise level. Since the aging device  37 - 1  supplies an output signal corresponding to a change in level between T a (=0) and T b (=the time when the output signal level reaches the noise level), the side for receiving the output signal can determine whether or not a predetermined time period has elapsed, or can determine a specific time point (e.g. T 1 , T 2  or T 3  shown in  FIG. 7 ) a predetermined time period after the initial state if the relationship between the state of the aging device  37 - 1  and the level of the output signal is always clear. The time points T 1 , T 2  and T 3  correspond to the states  2 ,  3  and  4  in  FIG. 6 .  
         [0056]      FIG. 8  is a second example  37 - 2  that realizes the aging device  37  of  FIG. 4 . The aging device  37 - 2  comprises: a first layer having a source region  61 , drain region  62  and channel region  63  therebetween; a second layer provided on the first layer and formed of a tunnel insulation film  64 ; a third layer provided on the second layer and formed of a gate  65 ; and a PN junction  66  provided on the third layer for controlling a leak current. A source electrode  68  and drain electrode  69  are provided on the source and drain regions  61  and  62 , respectively.  
         [0057]     The change in the state of the aging device  37 - 2  with lapse of time is similar to that of the aging device  37 - 1 , although in the former, current leakage occurs in a PN junction, and in the latter, direct tunneling occurs. Therefore, no description is given of the change in the state of the aging device  37 - 2  with lapse of time.  
         [0058]      FIG. 9  is a third example  37 - 3  that realizes the aging device  37  of  FIG. 4 . The aging device  37 - 3  comprises: a first layer having a source region  71 , drain region  72  and channel region  73  therebetween; a second layer provided on the first layer and formed of a tunnel insulation film  74 ; a third layer provided on the second layer and formed of a gate  75 ; and a Schottky junction  76  provided on the third layer for controlling a leak current. A source electrode  78  and drain electrode  79  are provided on the source and drain regions  71  and  72 , respectively.  
         [0059]     The change in the state of the aging device  37 - 3  with lapse of time is similar to that of the aging device  37 - 1 , although in the former, current leakage occurs in a Schottky junction, and in the latter, direct tunneling occurs. Therefore, no description is given of the change in the state of the aging device  37 - 3  with lapse of time.  
         [0060]     As described above, a pre-process for forming a channel is needed before time measurement is started by the aging device  37 . In the embodiment, the pre-process is performed only when charging power is supplied from the IC card case  3  to the aging device  37 .  
         [0061]     Referring now to  FIG. 10 , the structure of the aging device  37  that incorporates the above-described change unit  41  will be described.  
         [0062]     In  FIG. 10 , a voltage can be applied between the opposite ends of the change unit  41 . A power supply terminal  81  is connected to the source electrode  58 ,  68 ,  78  of the aging device  37  via a switch element  83 , while a GND terminal  82  is connected to the drain electrode  59 ,  69 ,  79  via an ampere meter  84 .  
         [0063]     The switch element  83  is connected to an ON/OFF (enable) signal line that only instantly outputs an ON signal when the supply of power to the IC card  2  starts at the contact unit  31 . This signal is turned on when an ON signal is supplied.  
         [0064]     The ampere meter  84  is connected to output a current value to a comparator  85 . The comparator  95  receives a current value at one input terminal, and a predetermined threshold value at the other input terminal, and outputs a signal of the “H” or “L” level depending upon whether or not the current value is higher than the predetermined threshold value. The output of the comparator  85  is stored in a state register  86 . The state register  86  is connected so that the card identification unit  36  can refer to it. When data concerning the state of the aging device  37  is stored in the state register  86 , the card identification unit  36  turns on the switch element  83  to thereby apply a predetermined voltage between the power supply terminal  81  and GND terminal  82 . The current flowing through the change unit  41  is measured by the ampere meter  84 , the measured current value is converted into the “L” or “H” level by the comparator  85 , and the resultant “L” or “H” level is stored as the above-mentioned data. To refer to the state of the aging device  37 , the card identification unit  36  reads data concerning the state of the aging device  37  from the state register  86 .  
         [0065]     In the above example, a single change unit  41  is employed. However, the aging device  37  may incorporate a plurality of change units  41 .  FIG. 11  illustrates an aging device  37  in which a plurality of change units  41  is arranged in parallel, and the current values output from the units  41  are input to an averaging circuit  87 , thereby comparing the averaged current value with the threshold by the comparator  85  and storing the “L” or “H” level in the state register  86 . The ON/OFF (enable) signal line is connected to the respective switch elements  83  so that the switch elements  83  are commonly controlled. In this example, even if the change units  41  exhibit some different changes in state with lapse of time, their average value enables a stable aging device  37  to be realized.  
         [0066]     The IC card case  3  will now be described.  
         [0067]     The owner of the IC card  2  uses the IC card case  3  to house the IC card  2  therein when the owner does not use the card. One IC card case is assigned to each IC card  2 . In other words, only if the IC card uniquely corresponding to an IC card case is inserted therein, the IC card case operates normally.  FIG. 12  is a block diagram illustrating the configuration of an IC card case  3 .  
         [0068]     A contact unit  91  is exposed on the inner surface of the IC card case  3  so that it is electrically connected to the contact unit  31  of the IC card  2  when the IC card  2  is housed in the IC card case  3 .  
         [0069]     A cipher key storage  92  stores a cipher key assigned to the IC card  2 . A card identification unit  39  cooperates with the card identification unit  36  of the IC card  2  to determine whether or not the IC card  2  corresponds to the IC card case  3  when the IC card  2  is housed in the IC card case  3 . This mutual identification process may be performed utilizing, for example, the transmission protocol stipulated in the ISO/IEC7816 series. If the card identification unit  93  determines that the IC card  2  is legitimate, it informs a card lock unit  97  of this.  
         [0070]     A password storage  94  stores a password. If this password is set identical to that of the IC card  2 , the usability of the IC card case  3  is enhanced, while if the former is set different from the latter, the security is enhanced. Thus, it is advisable to set the password stored in the storage  94  according to purpose.  
         [0071]     An input unit  95  is used by a user to input the password so as to eject the IC card  2  from the IC card case  3 . The password identification unit  96  compares the input password with the stored one to determine the legitimacy of the user. If the password identification unit  96  determines that the user is legitimate, it informs the card lock unit  97  and aging activation unit  98  of this.  
         [0072]     When it is informed by the card identification unit  93  that the card is legitimate, the card lock unit  97  locks an IC card ejection mechanism (not shown). Further, when it is formed by the password identification unit  96  that the user is legitimate, the card lock unit  97  unlocks the IC chard ejection mechanism. The IC card case  3  may be modified such that the card identification unit  96  informs the card lock unit  97  of a user even if the user is determined to be illegitimate, and the card lock unit  97  does not unlock the IC card ejection mechanism for a predetermined time period even if the user is determined legitimate after they have been determined illegitimate several successive times. This structure further enhances the security.  
         [0073]     The aging activation unit  98  supplies aging-device-charging power to the IC card  2  via the contact unit  91  if the password identification unit  96  determines that the user is legitimate. This charging power is supplied using a terminal different from that used to drive each element in the IC card  2 .  
         [0074]     A power supply  99  is, for example a battery for supplying power, and is used to supply power to each element in the IC card case  3  and to each element in the IC card  2  via the contact unit  91 .  
         [0075]     A description will be given of operations, performed by the system constructed as above, for housing the IC card  2  into the IC card case  3 , ejecting the IC card  2  from the IC card case  3 , and using the IC card  2  in the IC card reader  1 .  
         [0076]     Firstly, referring to  FIG. 13 , the operation of housing the IC card  2  into the IC card case  3  will be described.  
         [0077]     After using the IC card  2 , the user inserts the IC card  2  into the IC card case  3  (S 11 ).  
         [0078]     When the IC card  2  is inserted in the IC card case  3 , mutual identification is performed by the card identification unit  36  of the IC card  2  and the card identification unit  93  of the IC card case  3  (S 12 ). As above-mentioned, this mutual identification process is performed utilizing, for example, the transmission protocol stipulated in the ISO/IEC7816 series.  
         [0079]     If the card identification unit  93  of the IC card case  3  determines that the IC card  2  is legitimate, it informs the card lock unit  97  of this (S 13 ). Upon receiving the information, the card lock unit  97  locks the ejection mechanism for ejecting the IC card  2  (S 14 ).  
         [0080]     On the other hand, if the card identification unit  93  of the IC card case  3  determines that the IC card  2  is illegitimate, the IC card  2  is forcedly ejected from the case by the ejection mechanism (S 15 ).  
         [0081]     The above procedure enables only the IC card uniquely corresponding to an IC card case to be stored therein.  
         [0082]     Referring to  FIG. 14 , a description will be given of the operation of ejecting the IC card  2  from the IC card case  3  to use the card.  
         [0083]     When a user utilizes the IC card  2 , the user firstly inputs a password for identification through the input unit  95  of the IC card case  3  (S 21 ). The input password is sent to the password identification unit  96 , where it is compared with the password read from the password storage  94  (S 22 ).  
         [0084]     If it is determined from the comparison that the two passwords are not identical to each other, nothing is performed. This means that the card lock unit  97  keeps the ejection mechanism locked, therefore the IC card  2  cannot be ejected.  
         [0085]     If, on the other hand, it is determined at the step S 22  that the two passwords are identical, this is reported to the aging activation unit  98 , which, in turn, charges the aging device  37  via the contact unit  91  (S 23 ).  
         [0086]     After that, the password identification unit  96  informs the card lock unit  97  that the two passwords are determined to be identical at the step S 22 , whereby the card lock unit  97  releases the ejection mechanism (S 24 ) to permit the IC card  2  to be ejected (S 25 ).  
         [0087]     Referring then to  FIG. 15 , the operation of permitting a user to use the IC card  2  will be described.  
         [0088]     Firstly, the user inserts the IC card  2  into the IC card reader  1  (S 31 ). In this state, the IC card  2  is charged with power by the IC card reader  1 . Upon the supply of power from the card reader  1  to the card  2 , an ON signal is supplied to the aging device  37 , whereby the aging device  37  stores data indicative of the present state of the change unit  41  in the state register (S 32 ).  
         [0089]     Subsequently, the user inputs the password of the IC card  2  to the IC card reader  1  through the input unit  22  (S 33 ). The password identification unit  24  of the IC card reader  1  reads the password from the password storage  33  of the IC card  22 , and compares the read password with the input password to determine whether or not they are identical (S 34 ). If they are not identical, it is determined that the user is illegitimate, thereby making it impossible to use the IC card  2  (S 35 ). At this time, for example, an error message is generated and the IC card  2  is ejected.  
         [0090]     On the other hand, if the passwords are determined to be identical at the step S 34 , the cipher key acquisition unit  25  reads an ID from the ID storage  34  of the IC card  2  (S 36 ), thereby issuing a request for a cipher key to the database  4  via the communication unit  26 , using the ID (S 37 ). As a result, the cipher key uniquely corresponding to the ID is acquired from the database  4  (S 38 ). The acquired cipher key is transferred to the card identification unit  27 .  
         [0091]     After that, the card identification unit  36  of the IC card  2  refers to the state of the aging device  37 , and determines whether or not the state of the aging device  37  indicates the elapse of a predetermined time period (S 39 ). If it is determined that the state of the aging device  37  indicates the elapse of the predetermined time period, the program proceeds to a step S 35 , whereas if the state of the aging device  37  indicates the elapse of a time period shorter than the predetermined time period, the program proceeds to a step S 40 .  
         [0092]     Further, if the state of the aging device  37  indicates the elapse of the predetermined time period, the card identification unit  36  of the IC card  2  may perform a process for changing part or the whole portion of a message that is used for identification and is sent to the card identification unit  27  of the IC card reader  1 . Alternatively, the unit  36  may send no message. In other words, if the state of the aging device  37  indicates the elapse of the predetermined time period, the card identification unit  36  may make it impossible to perform a correct identification process between the IC card reader  1  and IC card  2 .  
         [0093]     Thereafter, the card identification unit  27  cooperates with the IC card identification unit  36  of the IC card  2  to perform mutual identification (S 40 ), utilizing, for example, the transmission protocol stipulated in the ISO/IEC7816 series.  
         [0094]     If identification has succeeded at the step S 40 , services are provided (S 41 ). If identification has failed at the step S 40 , the use of the IC card  2  is prohibited (S 35 ). Of course, there may be a case where identification has failed at the step S 40  for reasons other than the reason that the aging device  37  indicates the elapse of the predetermined time period.  
         [0095]     The period of validity can be set in the above-described IC card  2  of the embodiment without providing the card with a power supply, such as a battery. Further, when the IC card  2  is ejected from a card case uniquely corresponding to the card, it is checked whether or not a legitimate user tries to use the card  2 , and then measurement of the period of use is started. Therefore, in light of the required period of use, the period of the validity of the card can be set to a relatively short period. When the period of validity is set short, even if the card  2  is lost and acquired by a third party, the possibility of illegal use by the third party is reduced because the period of validity will soon be expired. Thus, the security is enhanced.  
         [0096]     Further, after the expiration of a set period of validity, a legitimate user can use the IC card  2  again simply by charging the IC card  2  by the IC card case  3 , without a complicated operation (for example, accessing the service company to ask the resumption of use).  
         [0097]     In the embodiment, the function of making it impossible to use the IC card  2  after the expiration of the period of validity determined by the aging device  37  is realized by the card identification unit  36  that utilizes the information, on the state of the aging device  37 , held in the state register. The embodiment of the invention is not limited to this, but may be modified in various ways. For example, the power supply unit  38  may control the supply of power to each element based on the contents of the state register. Alternatively, a switch may be provided across the line between each element and the contact unit  31 , thereby performing ON/OFF control of the switch.  
         [0098]     Furthermore, in the embodiment, the aging device  37  is charged via the charging terminal of the contact unit  91 . However, a message (command for IC cards) for an identification process between the IC card  2  and IC card case  3  (performed using the transmission protocol stipulated in the ISO/IEC7816 series) can be utilized to charge the aging device  37 . Although the format of the message is determined by the protocol, part of the message can be set by a vender. Accordingly, the instruction to charge the aging device  37  may be contained in the message sent from the IC card case  3  to the IC card  2 , thereby making the power supply unit  38  of the IC card  2  charge the aging device  37 .  
         [0099]     Although in the embodiment, the user identification is performed utilizing password identification, another identification system, such as fingerprint identification or biological identification, can be utilized.  
         [0100]     Also, in the embodiment, the protocol used for the card identification process between the IC card  2  and IC card reader  1  is also used for that between the IC card  2  and IC card case  3 . However, a dedicated protocol may be used for the card identification process between the IC card  2  and IC card case  3 , since it does not influence the existing IC card systems.  
         [0101]     In addition, in the embodiment, the IC card  2  is inserted into the IC card reader  1 , and their contact units are connected. However, the connection method is not limited to this. For example, the IC card  2  and IC card reader  1  may have their respective coils capable of receiving electromagnetic waves, so that they can be connected to each other out of contact with each other.  
         [0102]     The above-described IC card system has been devised to consider the case where only the IC card  2  is lost. Since, however, the IC card case  3  is also carried by an IC card owner, it is possible to lose the IC card case  3  with the IC card housed therein. In light of this, the power supply  99  of the IC card case  3  may be constructed such that it is charged only by the charger dedicated thereto. By virtue of this structure, the security is further enhanced. Lastly, a modification, in which this structure is added to the above-described embodiment, will be described.  
         [0103]      FIG. 16  is a block diagram illustrating a charger  6 .  
         [0104]     The charger  6  has the same shape as the IC card  2 , and is constructed such that an AC cord  102  is exposed to the outside when the charger  6  is attached to the IC card case  3 .  
         [0105]     As shown in  FIG. 16 , to attach the charger  6  to the IC card case  3 , a contact unit  101  is opposed to the contact unit  91  of the IC card case  3 . When the charger  6  is attached to the IC card case  3 , the contact units  101  and  91  are electrically connected.  
         [0106]     A cipher key storage  104  stores the same cipher key as that for the IC card  2 .  
         [0107]     A card identification unit  103  cooperates with the card identification unit  93  of the IC card case  3  to determine whether or not the IC card case  3  uniquely corresponds to the charger  6  when they are attached to each other. The card identification unit  103  transmits and receives messages, using the cipher key stored in the cipher key storage  104 , and performs identification using the transmission protocol stipulated in the ISO/IEC7816 series. If the card identification unit  103  determines that the IC card case  3  is legitimate, it permits AC power to be supplied from the AC cord  102 , connected to an AC power supply (not shown), to the IC card case  3  via the contact unit  101 . The power supply  99  of the IC card case  3  is charged with the AC power. If it is determined as a result of mutual identification that the IC card case  3  is illegitimate, no power is supplied from the AC cord  102  to the contact unit  101 .  
         [0108]     As described above, the charger  6  employed in the modification charges the IC card case  3  after the legitimacy of the case is confirmed by card identification. Even if the IC card case  3  with the IC card  2  housed therein is lost and a third party acquires it, the third party cannot illegally utilize the IC card  2 . This is because the power remaining in the IC card case  3  is consumed while the third party is trying to eject the card  2  from the case  3  by repeatedly inputting random passwords, and because once the power has been consumed, no further power can be charged in the power supply  99  of the IC card case  3 , thereby preventing illegal use of the IC card  2 .  
         [0109]     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.