Abstract:
To provide a mechanism for preventing information leakage by erasing stored information if a preset condition is not satisfied, because if an external storage device in which the information is stored is stolen or lost the risk of information leakage through decryption still remains even in the case where the information is encrypted. An external storage device has a locking management function capable of setting available conditions for stored information and controlling permission/prohibition of user access depending on whether the conditions are satisfied. User access is permitted if the available conditions are satisfied. The stored information is erased if the available conditions are not satisfied.

Description:
INCORPORATION BY REFERENCE 
       [0001]    This application claims priority based on a Japanese patent application, No. 2006-312361 filed on Nov. 20, 2006, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a technique for safely carrying information that is stored in an external storage device such as a memory card. More particularly, the invention relates to a technique for preventing information leakage by managing information stored in an external storage device in such a manner that it can be used under a particular condition. 
         [0003]    In recent years, with the price reduction of personal computers (hereinafter abbreviated as PCs) and network equipment, a number of companies have come to distribute business terminals such as PCs to employees and let them work using those terminals. As PC prices decrease and more PCs come to be used, chances of leakage of highly secret information and like information in a company increase. As a countermeasure, for example, dedicated terminals not having a mechanism of storing information have been conceived. Information leakage due to loss of a terminal can be prevented by performing business processing while receiving image information by remotely manipulating a server installed in a company via a communication line with the use of the terminals. However, since this method is based on securing of a communication line, a mechanism which allows safe carrying of information and is free of risk of information leakage is desired in the case where no communication line can be secured. 
         [0004]    On the other hand, in recent years, IC cards (also called smart cards) incorporating a processor (central processing unit, CPU) called an IC chip have come to attract much attention as devices having an authentication function. Since IC cards have a computation function themselves, when receiving a read or write instruction from a host, they can judge, by themselves, whether the access is legitimate. Furthermore, incorporating a rewritable memory such as an EEPROM or a RAM, IC cards can store an application or information of a user or a card issuer. 
         [0005]    An IC card can authenticate a user or output information for denial prevention by performing a computation on externally input information using information (a secret key or the like) that exists only in the legitimate card. Therefore, an IC card can perform a control as to whether or not to output, to a reader/writer or a host, information stored in the IC card by collating user-input personal identification information with identification information held inside the card. 
         [0006]    Since CPUs cards themselves are difficult to forge, it is also difficult to falsify information issued by an IC card module (IC card chip) which is an anti-tampering device or to illegally access information stored in an IC card module. As such, IC cards make it possible to construct a system which is high in the security level. 
         [0007]    On the other hand, flash memory cards are known as memory cards which incorporate a large-capacity, nonvolatile memory module and allows rewriting of information held inside. Many flash memory cards are not provided with hardware resistance to an attack from a third party (i.e., tampering resistance). A non-tampering-resistant flash memory card is associated with not a low risk that when stolen or lost it is disassembled and information held therein leaks to a third party through analysis of its memory or controller. 
         [0008]    As described in Japanese Patent Laid-open Publication No. 2001-209773, a flash memory card having a flash memory interface and an IC card function is known. Because of its large storage capacity, this flash memory card having a flash memory interface and an IC card function is convenient to store, in the card, for carrying, a user&#39;s documents, system setting files, or the like originally stored in a personal computer or a workstation. 
       SUMMARY OF THE INVENTION 
       [0009]    In the above-described dedicated terminals such as PCs in which no information can be stored, the securing of a communication channel is indispensable and no work can be done unless a communication channel is secured. When such a situation is expected, it is necessary to store, for carrying, necessary information in a certain external storage device and do work using the information stored in the external storage device. In the event of such a situation, sufficient care should be taken so as not to lose the external storage device. It is common practice to encrypt information in storing it in the external storage device. However, even if information is encrypted, it may still leak through decryption. A mechanism for preventing information leakage at a high probability is thus desired. 
         [0010]    The present invention provides a mechanism for erasing information stored in an external storage device and thereby disabling access to it when it comes not to satisfy a preset available condition. 
         [0011]    Other objects and novel features of the invention will become apparent from the description of the specification and the accompanying drawings. 
         [0012]    Typical aspects of the invention will be outlined below. 
         [0013]    An external storage device according to the invention is provided with a nonvolatile storage element which is a medium for storing information (called storage information) and a control section for connecting the medium to a terminal or a PC. The nonvolatile storage element is configured so as to have a locking management function capable of prohibiting access from a user and to thereby allow setting of a use condition (available condition) for information stored in the nonvolatile storage element. 
         [0014]    The external storage device is further characterized in that access from a user is permitted if the use condition is satisfied and stored information is erased if the use condition is not satisfied. No limitations are imposed on the content of “information” as a subject of access provided that it should be digital information; it may be a program or data as a subject of processing of a PC. 
         [0015]    More specifically, one aspect of the invention provides an external storage device access system having an external storage device and a terminal apparatus, characterized in that the external storage device comprises a storage element in which an access-controlled area is set which is access-controlled on the basis of authentication information and a control section for access-controlling the storage element; and that the terminal apparatus comprises an input/output interface and an access management section for accessing the external storage device. 
         [0016]    The external storage device access system further characterized in that when the external storage device is connected to the input/output interface, the control section is activated in such a state that it refuses access to the access-controlled area; upon detection of the connection of the external storage device to the input/output interface, the access management section of the terminal apparatus sends, to the control section, a request, including authentication information of a user of the terminal apparatus, for permission of user access to the access-controlled area; the control section of the external storage device performs verification of the user authentication information received from the terminal apparatus; if the verification succeeds, the control section sends, to the terminal apparatus, a notice of permission of user access to storage information that is stored in the access-controlled area; and if the verification fails, the control section erases the storage information stored in the access-controlled area. 
         [0017]    The external storage device access system may be configured in such a manner that the control section sends a notice of the failure of the verification to the access management section of the terminal apparatus; that when receiving the notice of the failure of the verification, the access management section sends, to the control section, an instruction to erase the storage information stored in the access-controlled area; and that when receiving the instruction to erase the storage information, the control section erases the storage information stored in the access-controlled area. 
         [0018]    The external storage device access system may also be configured in such a manner that the access-controlled area comprises one or more use-condition-accompanied areas for which use conditions are set, respectively; that each of the use-condition-accompanied areas comprises a management information area for storing the use condition and a data area for storing the storage information; that if the verification of the user authentication information succeeds, the control section makes a transition to a state that it permits reading of the use conditions stored in the management information areas and can permit access to the storage information stored in the data areas; that when receiving, from the control section, the user access permission notice which is sent in response to the user access permission request, the access management section of the terminal apparatus sends, to the control section, an instruction to read the use conditions stored in the management information areas of the one or more use-condition-accompanied areas, checks whether or not to permit user access to the individual use-condition-accompanied areas on the basis of the read-out use conditions received form the control section, sends, to the control section, an instruction to erase the storage information stored in the data area of a use-condition-accompanied area for which user access has been refused, and sends, to the user, after erasure of the storage information, a notice of permission of access to the storage information stored in the data area of a use-condition-accompanied area for which user access has been permitted; that when receiving the use conditions reading instruction from the access management section of the terminal apparatus, the control section of the external storage device reads the use conditions stored in the management information areas and sends them to the terminal apparatus; and that when receiving, from the access management section of the terminal apparatus, the instruction to erase the storage information stored in the data area of the use-condition-accompanied area for which user access has been refused, the control section erases the storage information. 
         [0019]    Furthermore, the external storage device access system may be configured in such a manner that the external storage device further comprises a user authentication processing section for authenticating a user; that when the external storage device is connected to the input/output interface of the terminal apparatus and the terminal apparatus is activated, the access management section of the terminal apparatus stores input user authentication information and sends it to the user authentication processing section of the external storage device; that the user authentication processing section performs processing of authenticating the user using the received user authentication information and sends an authentication result to the access management section; that if the authentication result of the user authentication processing section indicates that the user is legitimate, the access management section uses the stored user authentication information as authentication information of the user of the terminal apparatus to be included in the request for permission of user access to the access-controlled area; and that if the authentication result indicates that the user is not legitimate, the access management section stops operation of the terminal apparatus. 
         [0020]    According to the above forms of the invention, since the use condition is set in advance, the external storage device can be used as one that allows access to its internal information as long as the use condition is satisfied. If the use condition comes not to be satisfied any more, the information stored in the external storage device is erased and hence cannot be accessed. This mechanism can provide an external storage apparatus with which the risk of leakage of the information stored therein is very low even if it is lost. 
       ADVANTAGE OF THE INVENTION  
       [0021]    The invention makes it possible to provide an external storage device which is very low in the risk of information leakage. 
         [0022]    These and other benefits are described throughout the present specification. A further understanding of the nature and advantages of the invention may be realized by reference to the remaining portions of the specification and the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  illustrates a connection form of an external storage device or a memory card and a terminal according to each embodiment of the invention. 
           [0024]      FIG. 2  illustrates a functional configuration of the terminal according to the first embodiment. 
           [0025]      FIG. 3  illustrates a first configuration of the memory card used in each embodiment. 
           [0026]      FIG. 4  illustrates a second configuration of the memory card used in each embodiment. 
           [0027]      FIG. 5  illustrates the structure of a nonvolatile storage area of the external storage device or the memory card according to the first embodiment and information to be stored in each management information area. 
           [0028]      FIG. 6  illustrates commands used in each embodiment. 
           [0029]      FIG. 7  illustrates a process flow (part  1 ) according to the first embodiment. 
           [0030]      FIG. 8  illustrates a process flow (part  2 ) according to the first embodiment. 
           [0031]      FIG. 9  illustrates an error handling flow according to the first embodiment. 
           [0032]      FIG. 10  illustrates the structure of a nonvolatile storage area of an external storage device or a memory card according to a second embodiment. 
           [0033]      FIG. 11  illustrates the functional configuration of a terminal according to the second embodiment. 
           [0034]      FIG. 12  illustrates a process flow according to the second embodiment. 
           [0035]      FIG. 13  illustrates a process flow according to the third embodiment. 
           [0036]      FIG. 14  illustrates a process flow according to a fourth embodiment showing how a manager sets management information in advance. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0037]    Embodiments of the present invention will be hereinafter described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote components having the same function and hence they will not be described redundantly. 
       First Embodiment  
       [0038]    An external storage device according to a first embodiment of the invention will be described below with reference to  FIGS. 1-10 . 
         [0039]      FIG. 1  shows a system configuration according to the first embodiment of the invention. An external storage device  1005  shown in  FIG. 1(A)  is composed of a control section  1003  and a nonvolatile storage element  1004 , and is connected to a terminal apparatus (hereinafter referred to as “terminal”)  1001  via a general-purpose input/output bus  1002 .  FIG. 1(B)  shows another external storage device  1005  which is composed of a nonvolatile memory card (hereinafter referred to as “memory card”)  1007  and a reader/writer  1006  which connects the memory card  1007  to a general-purpose input/output bus  1002 . In this case, as described later, the functions of the control section  1003  are divided into functions of the memory card  1007  and those of the reader/writer  1006 . 
         [0040]      FIG. 3  shows an exemplary configuration of the memory card  1007 . The memory card  1007  is composed of terminals  1201  for connection to the reader/writer  1006 , a control section  1202 , and a nonvolatile storage element  1203  for storing information (referred to as “storage information”). The nonvolatile storage element  1203  may have the same characteristics as the nonvolatile storage element  1004  shown in  FIG. 1 . The terminals  1201  may be a transmission/reception antenna for realizing a non-contact memory card. 
         [0041]      FIG. 4  shows another exemplary configuration of the memory card  1007 . This configuration is different from the configuration of  FIG. 3  in being further provided with an IC card chip  1303  which is connected to the control section  1202  via a signal line  1301 . With this configuration, the memory card  1007  of  FIG. 4  also has a user authentication function which is provided by the IC card chip  1303 . As described above, the control section  1202  shown in  FIG. 3  has part of the functions of the control section  1003  shown in  FIG. 1  and the reader/writer  1006  has the other part of the functions of the control section  1003  shown in  FIG. 1 . 
         [0042]    The control section shown in each figure is composed of a CPU, a nonvolatile memory, and an input/output circuit which are connected to each other by an internal signal line such as a bus. Programs for realizing individual pieces of processing (described later) of the control section are stored in the nonvolatile memory. The pieces of processing of the control section are realized by “processes” which are implemented by the CPU&#39;s running those programs. However, the following description will be made as if the control section performed the individual pieces of processing on its own. 
         [0043]    The nonvolatile storage element  1004  of the external storage device  1005  and the nonvolatile storage element  1203  of the memory card  1007  include an area called a private area  1041  (address A to address B; corresponds to an access-controlled area) which is access-controlled by the control section  1003  or  1202  which has received a command shown in  FIG. 5 .  FIG. 6  illustrates commands. 
         [0044]    For example, when supply of power to the external storage device  1005  or the memory card  1007  is started (e.g., when it is connected to the terminals  1001  or the reader/writer  1006 ) or when the external storage device  1005  or the memory card  1007  receives a locking command  1402  (corresponds to an access prohibition request) with authentication information or the like from the outside, the control section  1003  or  1202  thereafter prohibits external access to the information stored in the private area  1401 . If the control section  1003  or  1202  receives an unlocking command  1403  (corresponds to an access permission request) with correct authentication information from the outside, executes it, and judges that the authentication information is legitimate through verification, the control section  1003  or  1202  enables access. Information that is necessary for verification maybe stored in the control section  1003  or  1202 . 
         [0045]    To enable handling of the storage information even when a user forgets his or her authentication information or the authentication information becomes unknown because of, for example, retirement of a user, it is desirable that a manager locking command  1404  and a manager unlocking command  1405  be set in the private area  1401 . If the system is configured in such a manner that these commands require authentication information, illegal access by a non-legitimate manager can be prevented. 
         [0046]    With the above configuration, if the external storage device  1005  or the memory card  1007  receives a locking command  1402 , it is removed from the general-purpose input/output bus  1002  or the reader/writer  1006 , or the supply of power to it is terminated when it is in an access-enabled state as a result of execution of an unlocking command  1403 , an access-enabled state is not restored and, instead, a locked state (access-prohibited state) is established (even if it is connected again to the general-purpose input/output bus  1002  or the reader/writer  1006  or power supply is resumed). A higher level of safety is thus realized. 
         [0047]    As shown in  FIG. 5 , the private area  1401  includes one or more information containers  1501 . Each information container  1501  corresponds to a use-condition-accompanied area and, in each of the following embodiments, it is an area where to store information to be managed under the same available conditions. Each information container  1501  has a management information area  1502  in which available conditions are set and a data area  1503  for storing storage information. The manner of division of each information container  1501  is arbitrary. An expiration deadline area  1504 , a number-of-allowable-times-of-use area  1504 , etc. are defined in the management information area  1502 . 
         [0048]      FIG. 2  illustrates the configuration of the terminal  1001 . In the terminal  1001 , a CPU  1101 , a main memory  1102 , a read-only memory  1103 , a display function circuit  1104 , and an input/output circuit  1105  are connected to each other by an internal signal line such as a bus. The input/output circuit  1105  includes a keyboard interface (interface will be abbreviated as IF)  1106 , a mouse IF  1107 , a printer IF  1108 , a general-purpose input/output IF  1109 , etc. The general-purpose input/output IF  1109  enables use of the general-purpose input/output bus  1002  to which the external storage device  1005  or the reader/writer  1006  is to be connected. 
         [0049]    Programs such as a locking management program  1110  and an operating system (not shown; hereinafter abbreviated as OS) are stored in the read-only memory  1103 . A “process” for realizing a piece of processing (described in each of the following embodiments) of the terminal  1001  is constructed in the terminal  1001  by the CPU  1101 &#39;s running these programs. However, for convenience, the following description will be made as if these programs performed each piece of processing on their own. 
         [0050]    An access management section is realized by cooperation between the locking management program  1110  and the operating system. Storing the locking management program  1110  in the read-only memory  1103  makes it difficult for a user to make illegal alterations. This configuration makes it possible to increase the level of safety because illegal access to the management information stored in the external storage device  1005  or the memory card  1007  is made difficult. 
         [0051]    A flow of operation that is performed after the external storage device  1005  or the memory card  1007  being in a locked state is inserted into the terminal  1001  or the reader/writer  1006  will be described below with reference to  FIGS. 7-9 . 
         [0052]    A user connects the external storage device  1005  or the memory card  1007  to the general-purpose input/output bus  1002  of the terminal  1001  (step  1601 ). 
         [0053]    The OS detects, via the general-purpose input/output IF  1109 , that the external storage device  1005  or the memory card  1007  has been connected to the general-purpose input/output bus  1002  (step  1602 ). 
         [0054]    In response, the OS instructs the locking management program  1110  to start activation processing (step  1603 ). 
         [0055]    The locking management program  1110  requests the user to input authentication information which is necessary for unlocking the private area  1401  (step  1604 ). 
         [0056]    In response, the user inputs authentication information (step  1605 ). For example, the authentication information is a password that the user inputs through a keyboard. However, the authentication information is not limited to it and may be biometric information such as a finger vein pattern which is obtained through a reading device (not shown). 
         [0057]    The locking management program  1110  sends an unlocking command  1403  with the input authentication information to the external storage device  1005  or the memory card  1007  (step  1606 ). Before sending the unlocking command, the locking management program  1110  may perform part of processing to be performed on the authentication information. 
         [0058]    Receiving the unlocking command, the control section  1003  or  1202  of the external storage device  1005  or the memory card  1007  verifies the authentication information. If judging that the authentication information is legitimate, the control section  1003  or  1202  unlocks the private area  1401 . If judging that the authentication information is not legitimate, the control section  1003  or  1202  leaves the private area  1401  in the locked state. And the control section  1003  or  1202  returns the verification result to the locking management program  1110  as a response (step  1607 ). 
         [0059]    At a judgment step  1608 , it is judged whether or not unlocking processing has been performed. 
         [0060]    If unlocking processing has not been performed and the locked state is maintained, error handling (step  1609 ) is performed. 
         [0061]    If unlocking processing has been performed, since the external storage device  1005  or the memory card  1007  has become usable, the locking management program  1110  instructs the external storage device  1005  or the memory card  1007  to read management information from one information container  1501  of the private area  1401  (step  1610  in  FIG. 8 ) and receives the management information (step  1611 ). 
         [0062]    The locking management program  1110  checks the available conditions contained in the management information and judges whether or not the use, by the user, of the storage information stored in the data area  1503  of the information container  1501  is legitimate (step  1612  in  FIG. 8 ). 
         [0063]    If the available conditions are not satisfied (step  1612 : no), the locking management program  1110  instructs the external storage device  1005  or the memory card  1007  to erase the storage information of the information container  1501  (step  1701 ). The control section  1003  or  1202  of the external storage device  1005  or the memory card  1007  reports a processing result to the locking management program  1110  (step  1702 ). 
         [0064]    If the available conditions are satisfied (step  1612 : yes) and if they include the number of allowable times of use, the locking management program  1110  updates it to a remaining number of allowable times of use (step  1703 ). 
         [0065]    The locking management program  1110  judges whether all the information containers  1501  have been processed (step  1704 ). If not all the information containers  1501  have been processed, the process returns to step  1610  to start processing another information container  1501 . 
         [0066]    Various available conditions can be set by the manager, examples of which are an expiration deadline and the number of allowable times of use. Only one available condition may be employed. Or plural available conditions may be combined arbitrarily. 
         [0067]    For example, a setting “effective until 18:30 of Dec. 31, 2006” is possible. Another condition such as “the number of allowable times of use is five” may be added. Where plural available conditions are set, the operation procedure is formulated so that the storage information is made usable if all of the plural conditions are satisfied. 
         [0068]    The manager writes available conditions to the management information areas  1502  in advance for each information container  1501 . 
         [0069]    An exemplary method by which the manager sets management information for each information container  1501  will be described later with reference to  FIG. 14  (fourth embodiment) If all judgments have been made and it has been found that the available conditions of all the information containers  1501  are satisfied or information containers  1501  whose available conditions are not satisfied have been subjected to the above-mentioned erasure processing, the locking management program  1110  reports, to the OS, that information containers  1501  whose available conditions are satisfied have become usable (step  1614 ). 
         [0070]    If use statuses such as the numbers of allowable times of use have also been checked at step  1612 , updated (i.e., latest) values are written to the management information areas  1502 . 
         [0071]    Only after receiving the above report, the OS informs the user that the external storage device  1005  or the memory card  1007  has become usable and a state that a next manipulation can be received has been established (step  1615 ). 
         [0072]    That is, the user is forced to stand by and cannot use the external storage device  1005  or the memory card  1007  during a period from the insertion of the external storage device  1005  or the memory card  1007  (step  1601 ) to the notification from the OS (step  1615 ). The last two steps (i.e., the reporting to the OS and the notification from the OS) are not indispensable. 
         [0073]    If there is an information container  1501  whose storage information has been erased, information indicating that information container  1501  may be presented to the user at step  1615 . Alternatively, the OS may refrain from informing the user of the fact that there is an information container  1501  whose storage information has been erased. 
         [0074]    In error handling (step  1609 ,  1917 , or  2009 ), the following processing shown in  FIG. 9  is performed. 
         [0075]    It is judged whether the number of times of occurrence of an authentication information input error has reached a preset number (step  1720 ). 
         [0076]    If it is smaller than the preset number (step  1720 : “smaller than the preset number”), the process returns to step  1604  in  FIG. 7 , where the locking management program  1110  again prompts the user to input correct authentication information. If it has reached the preset number (step  1720 : “the preset number is reached”), the locking management program  1110  judges that the current user is not a legitimate one and erases the storage information of all the information containers  1501  of the private area  1401  according to the following procedure. 
         [0077]    First, the locking management program  1110  sends a manager unlocking command (denoted by  1405  in  FIG. 6 ) to the external storage device  1005  or the memory card  1007  as an instruction to unlock the private area  1401  (step  1723 ). Authentication information is not indispensable for the manager unlocking command which is sent at step  1723 . 
         [0078]    After receiving an unlocking report (step  1724 ), the locking management program  1110  issues an instruction to erase the storage information of all the information containers  1501  of the private area  1401  (step  1725 ). 
         [0079]    The control section  1003  or  1202  of the external storage device  1005  or the memory card  1007  erases the contents of all the information containers  1501  and sends a report (step  1726 ). 
         [0080]    The locking management program  1110  informs the OS of the report (step  1727 ). Since the storage information of the information containers  1501  has been erased, the locking management program  1110  may either issue or not issue a manager locking command corresponding to step  1723 . 
         [0081]    The OS may inform the user of the fact that the storage information has been erased (step  1728 ). 
         [0082]    As is understood from the above process, information leakage can be prevented more reliably by detecting use by a non-legitimate user and erasing the contents of the information containers  1501 . 
       Second Embodiment  
       [0083]    An external storage device according to a second embodiment of the invention will be described below with reference to  FIGS. 10-12 . 
         [0084]      FIG. 10  shows a method for managing the storage area of the nonvolatile storage element  1004  or  1203  of the external storage device  1005  or the memory card  1007  in such a manner that it is divided into two areas. For example, the storage area from address A to address B of the nonvolatile storage element  1004  or  1203  is divided at a halfway address C. The first half (address A to address C) is made a public area  1451  for which no access control is performed and which can therefore be used anytime by anyone, and the second half (address C to address B) is made a private area  1452  which is similar to the private area  1401  of the first embodiment. 
         [0085]    A locking management program  1453  which is equivalent to the locking management program  1110  of the first embodiment is stored in the public area  1451  in advance. Since the locking management program  1453  is stored in the public area  1451 , it is not necessary to store the locking management program  1110  in the read-only memory  1103  of the terminal  1001  in advance (the OS is stored in the read-only memory  1103  as in the first embodiment). 
         [0086]      FIG. 11  shows the above-described setting of the terminal  1001 . The locking management program  1110  which is stored in the read-only memory  1103  in the first embodiment is not necessary. Instead, when the external storage device  1005  or the memory card  1007  is attached to the terminal  1001 , the locking management program  1453  is read from the public area  1451  and stored in the main memory  1102 . Then, a process similar to the process of the first embodiment can be executed when the locking management program  1453  is activated by automatic execution or activated explicitly by the user. 
         [0087]      FIG. 12  shows how the above-mentioned automatic execution is done. 
         [0088]    The user connects the external storage device  1005  or the memory card  1007  to the terminal  1001  (step  1801 ). The OS detects insertion information. At this time, if an automatic execution function is effective in the OS, the OS issues an instruction to read the locking management program  1453  which is stored in the public area  1451  (step  1803 ). 
         [0089]    The OS stores the locking management program  1453  in the main memory  1102  (step  1804 ). After being stored in the main memory  1102 , the locking management program  1453  is activated in the same manner as at step  1603  by the function of the OS or an explicit instruction from the user (step  1805 ). The subsequent process is the same as in the first embodiment. 
         [0090]    In this embodiment, it is desirable that prior to step  1801  the OS performs user authentication processing to prevent illegal access for, for example, rewriting of the management information by a non-legitimate user. 
       Third Embodiment  
       [0091]    A third embodiment is directed to a case that the manner of use of a locking command (see  FIG. 6 ) is simplified. 
         [0092]    This embodiment can be applied to a case that whether the user is legitimate can be checked by using the external storage device  1005  or the memory card  1007  when the terminal  1001  is activated. For example, this embodiment can be applied to a case that the memory card  1007  has the configuration of  FIG. 4  and that whether the user is legitimate can be verified by using the IC card chip  1303  incorporated in the memory card  1007  according to the public key base technology when the terminal  1001  is activated. 
         [0093]    A process flow of this embodiment will be described below with reference to  FIG. 13 . 
         [0094]    The OS starts terminal activation processing (step  1901 ), and requests the user to make a log-in input (step  1902 ). 
         [0095]    The user inserts the memory card  1007  for the purpose of authorization (step  1903 ). 
         [0096]    Then, the OS requests the user to input authentication information for the purpose of user authentication (step  1905 ). 
         [0097]    The OS stores authentication information that has been input by the user (step  1906 ) and sends it to the memory card  1007  (step  1907 ). 
         [0098]    The IC card chip  1303  of the memory card  1007  judges, on the basis of the user-input authentication information, whether or not the user is a registered, legitimate one and returns a response to the OS (step  1908 ). 
         [0099]    If the response indicates that the user is not a legitimate one, the OS performs processing  1910  of stopping the operation of the terminal  1001 . The process is then finished. 
         [0100]    If the user is a legitimate one, the OS performs processing  1911  of activating the locking management program  1110  to unlock the memory card  1007 . At this time, the OS passes the user&#39;s stored authentication information to the locking management program  1110  and the locking management program  1110  sends an unlocking command  1403  with the authentication information to the memory card  1007  (step  1912 ). As in the case of the first embodiment, part of the authentication information to be sent may have already been processed. 
         [0101]    Since the locking management program  1110  receives the authentication information from the OS and stores it, it is not necessary to request the user to input authentication information again. This is because whether the user is a legitimate one has already been judged at step  1909  when the terminal  1001  was activated. 
         [0102]    The subsequent process is the same as in the first embodiment. 
         [0103]    The above three embodiments are not limited to the case that only one set of a locking command  1402  and an unlocking command  1403  are provided. As shown in  FIG. 6 , a manager locking command  1404  and a manager unlocking command  1405  may also be provided. Providing commands that are dedicated to the manager separately from the ordinary commands allows the manager to give an instruction to unlock or lock the memory card  1007  using the manager locking command  1404  or the manager unlocking command  1405  even in the case where the ordinary command cannot be used for a certain reason, for example, in the case where the user forgets his or her authentication information or the user&#39;s authentication information is unknown because of his or her absence. Also in this case, it is desirable to set authentication information to prevent limitless unlocking by all managers who are supposed to deal with the system. 
       Fourth Embodiment  
       [0104]    An exemplary method by which the manager sets management information for each information container  1501  will be described below with reference to  FIG. 14 . 
         [0105]    The manager connects the external storage device  1005  or the memory card  1007  to the general-purpose input/output bus  1002  of the terminal  1001  (step  2001 ). 
         [0106]    When the OS detects, via the general-purpose input/output IF  1109 , that the external storage device  1005  or the memory card  1007  has been connected to the general-purpose input/output bus  1002  (step  2002 ), the OS instructs the locking management program  1110  to start activation processing (step  2003 ). 
         [0107]    The locking management program  1110  requests the manager to input authentication information to unlock the private area  1401  (step  2004 ). 
         [0108]    The manager informs the locking management program  1110  that the manager is going to do writing to the management information areas  1502  and inputs manager authentication information (step  2005 ). 
         [0109]    The locking management program  1110  sends a manager unlocking command  1405  with the input authentication information to the external storage device  1005  or the memory card  1007  (step  2006 ). 
         [0110]    When receiving the unlocking command, the control section  1003  or  1202  of the external storage device  1005  or the memory card  1007  verifies the authentication information. If judging that the manager is a legitimate one, the control section  1003  or  1202  unlocks the private area  1401  and enables writing to and update of the management information areas  1502  of the information containers  1501 . If judging that the manager is not a legitimate one, the control section  1003  or  1202  maintains the locked state and returns the check result to the locking management program  1110  as a response (step  2007 ). 
         [0111]    At a judgment step  2008 , the locking management program  1110  judges whether the manager was judged as a legitimate one. 
         [0112]    If the manager was not judged as a legitimate one and the locked state is maintained, error handling is performed (step  2009 ). 
         [0113]    If the manager was judged as a legitimate one and unlocking was effected, since writing to or update of the management information areas  1502  has been enabled, the locking management program  1110  prompts the manager to do writing to or update of the management information area  1502  for each information container  1501  (step  2010 ). 
         [0114]    The manager inputs management information for an information container  1501  to be set (step  2011 ), and the locking management program  1110  does writing to or update of the management information area  1502  of the subject information container  1501  of the external storage device  1005  or the memory card  1007  (step  2012 ). 
         [0115]    When the locking management program  1110  has completed the writing to or update of the management information area  1502  of the subject information container  1501  of the private area  1401 , the locking management program  1110  performs locking processing using a manager locking command  1404  (step  2013 ). 
         [0116]    Information to be used for user authentication at step  1607  by the control section  1003  or  1202  is stored in the control section  1003  or  1202  as is done in the above process after the manager authentication. 
         [0117]    The above-described four embodiments or part of them can be practiced in combination as appropriate. 
         [0118]    As described above, in the external storage device  1005  or the memory card  1007  according to each of the above embodiments, the locking management program  1110  or  1453  can manage the private area  1401  or  1452  safely. Therefore, an external storage device  1005  or a memory card  1007  can be constructed which assures safety of a user and is easy to use. 
         [0119]    Therefore, according to the embodiments, the usability of a user is increased even in an environment in which a communication line cannot be secured. Furthermore, even if the external storage device  1005  or the memory card  1007  is stolen or lost, the stored contents are erased upon occurrence of an illegal access manipulation by a third party. The risk of information leakage is thus very low. 
         [0120]    The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereto without departing from the spirit and scope of the invention as set forth in the claims.