Abstract:
Provided is a distributed authentication system and a communication control apparatus which allow a user to use a service with retained security. The distributed authentication system includes: a terminal; a communication control apparatus; and a server for distributing a service, the terminal, the communication control apparatus, and the server being connected to one another through a communication network, the communication control apparatus controlling communication between the terminal and the server, and in the system: the communication control apparatus includes a judgment module for judging whether to approve an access request from the terminal to the server; and the judgment module calculates a security level for the access request, requests the terminal to retrieve detailed information corresponding to the calculated security level, and approves the access request by authenticating the terminal of an access request source based on the detailed information received from the terminal.

Description:
CLAIM OF PRIORITY  
       [0001]     The present application claims priority from Japanese application P2005-077087 filed on Mar. 17, 2005, the content of which is hereby incorporated by reference into this application.  
       BACKGROUND  
       [0002]     This invention relates to a distributed authentication system and a communication control apparatus which allow a user to use a service with retained security.  
         [0003]     A network system is known to have a configuration including a terminal and a plurality of service distributors, in which the terminal transmits an access request to each service distributor. Upon receiving the access request from a user of the terminal, the service distributor requests an authentication server, which is connected to the service distributor, to authenticate the user. When having authenticated the user as eligible, the authentication server issues a notification to that effect to the terminal. Then, the service distributor distributes a service to the terminal.  
         [0004]     When the user of the terminal uses services provided by a plurality of service distributors, it is required to perform authentication processing for each service distributor in order to retain security. Therefore, it is required for the user to perform different complicated authentication processing for each service.  
         [0005]     Also, there exists a system which employs a network to group a plurality of users and provide various kinds of services. Further, there exists a system in which recommended information or service is provided to an individual user according to a preference or behavior history of the user.  
         [0006]     For instance, a single sign-on authentication method is known, in which a first authentication processing and a second authentication processing are carried out (see JP 2002-335239 A, for instance). In the first authentication processing, a first authentication server having received a content request from an authentication client terminal operated by a user carries out authentication of the user, holds an authentication state that is a result of the execution of the authentication, and creates and issues an authentication token showing the authentication state, while in the second authentication processing, a second authentication server having received the content request from the authentication client terminal operated by the user performs processing concerning the authentication of the user using the authentication token created and issued in the first authentication processing.  
         [0007]     Also, a path extraction apparatus is known which, has network topology information, network resource information, service attribute information in which service attributes are set, and network attribute information in which network attributes are set, selects a network suited for a service based on the service attribute information and the network attribute information, and obtains path information in the selected network based on the network topology information and the network resource information (see JP 2004-260671 A, for instance).  
       SUMMARY  
       [0008]     According to the technique described in JP 2002-335239 A, however, it is impossible to provide an, optimum authentication scheme with which optimum security is retained according to a user and a service. Also, with the technique described in JP 2004-260671 A, it is possible to select a network suited for a service using the attribute information but it is impossible to provide optimum security.  
         [0009]     In addition, there is a problem in that a user is required to carry out various settings and complicated authentication processing for each service that he/she wants to use, which lowers user convenience. Desired is a system capable of providing an environment having a network in which many information terminals perform communication, which allows use of a service through simple settings and authentication processing while retaining security suited for the service. With the conventional techniques, however, security is retained by performing authentication processing for each service at an individual server and it is not guaranteed that optimum authentication means is determined.  
         [0010]     It is therefore an object of this invention to judge a security level with reference to service content information and user context information and provide a user with an authentication scheme that is optimum to retain security corresponding to the security level. It is another object of this invention to, when a terminal of the user has moved, allow the user to continuously use a service with safety without performing another authentication processing.  
         [0011]     In order to solve the above problem, according to this invention, there is provided a distributed authentication system includes: a terminal; a communication control apparatus; and a server for distributing a service, the terminal, the communication control apparatus, and the server being connected to one another through a communication network, the communication control apparatus controlling communication between the terminal and the server, and in the system: the communication control apparatus includes a judgment module for judging whether to approve an access request from the terminal to the server; and the judgment module calculates a security level for the access request, requests the terminal to retrieve detailed information corresponding to the calculated security level, and approves the access request by authenticating the terminal of an access request source based on the detailed information received from the terminal.  
         [0012]     According to an embodiment of this invention, by applying authentication means suited for a service designated by an access request from a terminal, it becomes possible to retain security corresponding to circumstances. Also, it becomes possible to allow a user to use a service with safety without performing complicated authentication processing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a construction diagram of a distributed authentication system according to a first embodiment of this invention.  
         [0014]      FIG. 2  is a block diagram of a construction of a communication control apparatus according to the first embodiment of this invention.  
         [0015]      FIG. 3  is an explanatory diagram of an example of a user context information according to the first embodiment of this invention.  
         [0016]      FIG. 4  is an explanatory diagram of an example of a service content information according to the first embodiment of this invention.  
         [0017]      FIG. 5  is an explanatory diagram of an example of a user authentication processing information according to the first embodiment of this invention.  
         [0018]      FIG. 6  is an explanatory diagram of a judgment table according to the first embodiment of this invention.  
         [0019]      FIG. 7  is a sequence diagram of authentication processing according to the first embodiment of this invention.  
         [0020]      FIG. 8  is another sequence diagram of the authentication processing according to the first embodiment of this invention.  
         [0021]      FIG. 9  is a flowchart of processing executed by the communication control apparatus according to the first embodiment of this invention.  
         [0022]      FIG. 10  is a flowchart of processing executed by a terminal according to the first embodiment of this invention.  
         [0023]      FIG. 11  is a construction diagram of a distributed authentication system according to a second embodiment of this invention.  
         [0024]      FIG. 12  is a sequence diagram of authentication processing according to the second embodiment of this invention.  
         [0025]      FIG. 13  is another sequence diagram of the authentication processing according to the second embodiment of this invention.  
         [0026]      FIG. 14  is a flowchart of processing executed by a communication control apparatus according to the second embodiment of this invention.  
         [0027]      FIG. 15  is a construction diagram of a distributed authentication system according to a third embodiment of this invention.  
         [0028]      FIG. 16  is a sequence diagram of authentication processing according to the third embodiment of this invention.  
         [0029]      FIG. 17  is another sequence diagram of the authentication processing according to the third embodiment of this invention.  
         [0030]      FIG. 18  is a construction diagram of a distributed authentication system according to a fourth embodiment of this invention.  
         [0031]      FIG. 19  is a sequence diagram of authentication processing according to the fourth embodiment of this invention.  
         [0032]      FIG. 20  is a construction diagram of a distributed authentication system according to a fifth embodiment of this invention.  
         [0033]      FIG. 21  is another construction diagram of the distributed authentication system according to the fifth embodiment of this invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]     Hereinafter, distributed authentication systems according to embodiments of this invention will be described with reference to the accompanying drawings.  
       First Embodiment  
       [0035]      FIG. 1  is a construction diagram of the distributed authentication system according to the first embodiment of this invention.  
         [0036]     In the distributed authentication system of this embodiment, a terminal  10  ( 10 A to  10 N), communication control apparatuses  20 , and a server ( 31 A and  31 B) of a service distributor  30  ( 30 A and  30 B) are connected through a communication network (network).  
         [0037]     In each of the terminals  10 A to  10 N, a program that operates according to instructions from a user has been installed. This program requests service distributed by the service distributor  30 A or  30 B connected through the network. It should be noted that in the distributed authentication system of this embodiment, N terminals are connected and operate but in the following description, only an operation of the terminal  10 A will be described for ease of explanation.  
         [0038]     The communication control apparatus  20  receives an access request from the terminal  10 A and carries out authentication processing corresponding to the request from the terminal  10 A. When having authenticated the terminal  10 A as eligible, the communication control apparatus  20  issues a notification to the service distributor  30 A or  30 B for which the access request has been issued.  
         [0039]     The servers  31 A and  31 B of the service distributors  30 A and  30 B distribute service requested by the terminal  10 A. These servers  31 A and  31 B each include a program and provide the terminal  10 A with the content of the service through the network.  
         [0040]     It should be noted that in the distributed authentication system in this embodiment, the terminal  10 A, the communication control apparatus  20 , and the servers  31 A and  31 B are connected to each other through the network but a construction may be used instead in which they are connected to each other through a wide-area network such as the Internet.  
         [0041]     An operation of this distributed authentication system will be described. When the terminal  10 A requests the content of the service distributed by the service distributor  30 A, the following processing is carried out.  
         [0042]     First, the terminal  10 A transmits an access request to the communication control apparatus  20  (S 100 ). This access request contains information about the terminal  10 A, information about a user of the terminal  10 A, and information about the requested content. Upon receiving the access request from the terminal  10 A, the communication control apparatus  20  performs authentication processing based on the information about the terminal, the information about the user, and the information about the requested content contained in the request. When having authenticated the terminal  10 A as eligible, the communication control apparatus  20  delivers a policy to the server  31 A of the service distributor  30 A (S 120 ). This policy contains information about the content of the service requested by the user, a notification showing that the user has already been authenticated as eligible, and the address of the terminal  10 A that issued the request.  
         [0043]     The server  31 A receives the delivered policy and refers to the contents of the policy. Then, the server  31 A distributes the content of the service to the terminal  10 A that issued the request (S 130 ).  
         [0044]     On the other hand, when it is impossible to authenticate the terminal  10 A as eligible only with the information contained in the access request from the terminal  10 A, the communication processing apparatus  20  requests the terminal  10 A to further transmit detailed information (S 110 ). This detailed information contains information for authentication such as a password.  
         [0045]     Upon receiving the request for the detailed information transmission, the terminal  10 A transmits the detailed information to the communication processing terminal  20 . Upon receiving the detailed information from the terminal  10 A, the communication processing terminal  20  performs authentication processing based on the information contained in the detailed information. As a result, when having authenticated the terminal  10 A as eligible based on the information, the communication control apparatus  20  delivers a policy to the server  31 A of the service distributor  30 A (S 120 ). Upon receiving the delivered policy, the server  31 A distributes the content of the service to the terminal  10 A (S 130 ).  
         [0046]     Also, following this, when the content of service provided by the service distributor  30 B are desired, the terminal  10 A transmits an access request to the communication control apparatus  20  in a like manner (S 100 ). The communication control apparatus  20  performs authentication processing with reference to information contained in the received access request and information about the authentication processing that the terminal  10 A has already carried out. When having authenticated the terminal  10 A as eligible, the communication control apparatus  20  delivers a policy to the server  31 B of the service distributor  30 B like in the case described above (S 140 ). Upon receiving the delivered policy, the server  31 B distributes the content of the service to the terminal  10 A (S 150 ).  
         [0047]     On the other hand, when it is impossible to authenticate the terminal  10 A as eligible only with the information contained in the access request from the terminal  10 A, the communication control apparatus  20  requests the terminal  10 A to further transmit detailed information (S 110 ). Then, like in the case described above, the communication control apparatus  20  performs authentication processing based on the detailed information transmitted from the terminal  10 A. Following this, when having authenticated the terminal  10 A as eligible, the communication control apparatus  20  delivers a policy to the server  31 B of the service distributor  30 B (S 140 ). Upon receiving the delivered policy, the server  31 B distributes the content of the service to the terminal  10 A (S 150 ).  
         [0048]     It should be noted that in this case, when the terminal  10 A has already been authenticated as eligible in response to an access request and when a security level of an access request issued after the access request is lower than a security level of the preceding access request, the communication control apparatus  20  approves the succeeding access request without requesting the detailed information.  
         [0049]     As a result of this series of processing, it becomes unnecessary for the user of the terminal  10 A to send inquiries to the servers of the service distributors and perform authentication processing for respective contents of requested service. In other words, it becomes possible for the terminal  10 A to use the contents of a plurality of kinds of services merely by issuing access requests to one communication control apparatus  20 . In order to realize this, the communication control apparatus  20  receives all access requests from the terminal  10 A and delivers policies to the servers  31 A of the service distributors  30 A when the terminal has been authenticated as eligible. Upon receiving the delivered policies, the servers  31 A of the service distributors  30 A distribute the content of the service to the terminal  10 A.  
         [0050]      FIG. 2  is a block diagram of a construction of the communication control apparatus  20 .  
         [0051]     The communication control apparatus  20  includes an interface (I/F)  21 , a CPU  22 , a memory  23 , and a database  24 .  
         [0052]     The I/F  21  receives a request from another apparatus connected through the network and sends a result thereof.  
         [0053]     The CPU  22  reads various programs stored in the memory  23  and executes the programs.  
         [0054]     The memory  23  is constructed by a storage such as a DRAM. In the memory  23 , a communication program  231 , an encryption/decryption program  232 , a security/authentication level judgment program  233 , and a judgment table  234  are stored.  
         [0055]     The communication program  231  analyzes data received by the I/F  21 .  
         [0056]     The encryption/decryption program  232  encrypts data to be transmitted through the I/F  21  and decrypts encrypted data received through the I/F  21 .  
         [0057]     The security/authentication level judgment program  233  judges whether authentication of the content requested by the terminal  10 A should be permitted with reference to the information contained in the access request transmitted from the terminal  10 A and an authentication database  240  stored in the database  24 .  
         [0058]     The judgment table  234  is a table for judging an authentication level obtained from an authentication level of the user of the terminal  10 A that transmitted the access request and an authentication level of the content designated by the access request. This judgment table  234  is used by the security/authentication level judgment program  233 .  
         [0059]     The database  24  comprises a storage device such as a hard disk drive. In the database  24 , the authentication database  240  is stored. This authentication database  240  contains a user context information database (DB)  241 , a service content information database (DB)  242 , and a user authentication processing information database (DB)  243 .  
         [0060]     The user context information database  241  stores information about users who use service.  
         [0061]     The service content information database  242  stores information about the content of the service distributed by the service distributors  30 A and  30 B.  
         [0062]     The user authentication processing information database  243  stores the state (progress, result, or the like) of authentication performed by the security/authentication level judgment program  233  in response to the access request from the terminal  10 A.  
         [0063]      FIG. 3  is an explanatory diagram of an example of the user context information database  241 .  
         [0064]     The user context information database  241  stores a piece of user information for each registered user. Each piece of user information gives the “name”, “address”, “age”, “occupation”, “hobby”, and the like of a corresponding user, for instance. In addition, the piece of user information shows the security level of the corresponding user. The security level is a value showing the trustworthiness of the user. For instance, the security level is set high when the user was registered recently or caused trouble in the past and his/her trustworthiness is low. On the other hand, when the user uses service without causing trouble for a predetermined period of time or more after registration, the security level is set low. The security level is determined by the service distributor  30 , for instance.  
         [0065]      FIG. 4  is an explanatory diagram of an example of the service content information database  242 .  
         [0066]     The service content information database  242  stores information about the service distributed by the service distributors. The service content information database  242  includes a content type column  2421 , a server address column  2422 , and a content security level column  2423 . The content type column  2421  stores content type information such as “music”, “image”, and “ticket booking”. The server address column  2422  stores the addresses of servers that provide contents of service. The content security level column  2423  stores security levels set for the contents. For instance, in the case of “finance” service that requires a high level of security, the maximum value “5” is set in the security level column  2423 . Also, in the case of “Web access” service that does not require a high level of security, the minimum value “1” is set in the security level column  2423 .  
         [0067]      FIG. 5  is an explanatory diagram of an example of the user authentication processing information database  243 .  
         [0068]     The user authentication processing information database  243  stores the states (progresses, results, and the like) of authentication performed by the security/authentication level judgment program  233  in response to access requests from the terminals  10 A. The user authentication processing information database  243  includes a current state column  2431  and an authentication level column  2432 .  
         [0069]     The current state column  2431  stores the current authentication states of users of the terminals  10 A that has transmitted the access requests to the communication control apparatus  20 . The authentication level column  2432  stores identifiers indicating the authentication levels of users who have been authenticated as eligible. For instance, in the case of user “A”, “User A is permitted” is stored in an entry  2433  of the current state column  2431  and “25” is stored in an entry  2433  of the authentication level column  2432 . In other words, it can be understood that the user “A” has already been authenticated as eligible in response to his/her access request. Also, it can be understood that the authentication level of the user “A” is “25”.  
         [0070]      FIG. 6  is an explanatory diagram of the judgment table  234 .  
         [0071]     As described above, the judgment table  234  is a table used by the security/authentication level judgment program  233  to judge the authentication levels. The judgment table  234  includes an authentication level column  2341  and an authentication scheme column  2342 .  
         [0072]     The security/authentication level judgment program  233  calculates products of the security levels of the users and the security levels of the content of service requested by the users and judges to which authentication level ranges in the authentication level column  2341  the calculated values belong. Then, the security/authentication level judgment program  233  finds authentication schemes corresponding to the authentication level ranges from the authentication scheme column  2342 .  
         [0073]     The security levels of the users are acquired from the user context information database  241 . Also, the security levels of the content of the service are acquired from the service content information database  242 .  
         [0074]     Upon receiving an access request from the terminal  10 A, the security/authentication level judgment program  232  of the communication control apparatus  20  acquires information about the user and information about the content of service from information contained in the access request. Then, the security/authentication level judgment program  232  refers to the user context information database  241  and acquires a value of the security level of the user. Also, the security/authentication level judgment program  232  refers to the service content information database  242  and acquires a value of the security level of the content of the service designated by the request. Then, the security/authentication level judgment program  232  calculates a product of the acquired user security level value and content security level value and selects an authentication scheme with reference to a value of the product.  
         [0075]     For instance, when the content of the service requested by the user are “Web access”, the value of the security level of the content is “1”, and the value of the security level of the user is “1”, the authentication level becomes “1” that is a product of the security level values. The security/authentication level judgment program  232  refers to the judgment table  234  using this authentication level “1” as a key and selects “no authentication” from the authentication scheme column  2342 . As a result, the user is permitted to use the “Web access” service in response to the access request without performing authentication processing.  
         [0076]     It should be noted that in the case of an ordinary user who uses service frequently and caused no trouble in the past, the security level in the user context information is set at “1” because his/her trustworthiness is highest (security is lowest). Also, in the case of the “Web access”, it is not required to consider special security, so the security level is set at “1”.  
         [0077]     Also, when the content information of the requested service is “finance” service, the value of the security level of the content is “5”, and the value of the security level of the user is “5”, the authentication level becomes “25” that is a product of the security level values. The security/authentication level judgment program  232  refers to the judgment table  234  using this authentication level “25” as a key and selects “iris authentication scheme” from the authentication scheme column  2342 . The communication control apparatus  20  issues a request designating the iris authentication to the terminal  10 A. When the user has been authenticated as eligible as a result of the iris authentication, he/she is permitted to access the “finance” service.  
         [0078]     It should be noted that for each user who requested service for the first time, the security level of the user context information is set at “5” because his/her trustworthiness is lowest (security is highest).  
         [0079]     By stepwisely changing the levels of security of authentication, which the users are requested to perform, according to the products of the security levels of the users and the security levels of the content of the service requested by the users in the manner described above, it becomes possible to request the users to use authentication schemes, with which it is possible to retain high levels of security, in the case of access requests to service which requires high levels of security.  
         [0080]     Next, an operation of the distributed authentication system of this embodiment will be described.  
         [0081]      FIG. 7  is a sequence diagram of authentication processing according to this embodiment.  
         [0082]     The sequence diagram of  FIG. 7  shows processing in the case of service whose authentication level is low and which the user is capable of accessing without performing authentication.  
         [0083]     The terminal  10 A transmits an access request to the communication control apparatus  20  (S 100 ). This access request contains information about the user of the terminal  10 A, information about the content of service for which the access request has been issued, and the like.  
         [0084]     The communication control apparatus  20  receives the access request through the I/F  21 . The communication program  231  receives this access request, analyzes the contents thereof, and sends the request to the security/authentication level judgment program  233 . The security/authentication level judgment program  233  judges whether the access should be permitted with reference to the contents of the access request (S 101 ).  
         [0085]     When the security/authentication level judgment program  233  has approved the access request from the user without requesting detailed information (S 102 ), the communication program  231  transmits a notification showing that the access request has been approved to the terminal  10  through the I/F  21  (S 103 ).  
         [0086]     Upon receiving this access request approval, the terminal  10 A transmits an access request to the communication control apparatus  20  (S 104 ).  
         [0087]     Upon receiving the access request from the user of the terminal  10 A that has already been authenticated as eligible, the communication control apparatus  20  delivers a policy to the server  31 A of the service distributor  30 A (S 120 ). Upon receiving the policy, the server  31 A of the service distributor  30  distributes the service to the terminal  10 A according to the contents of the policy (S 130 ).  
         [0088]      FIG. 8  is another sequence diagram of the authentication processing according to this embodiment.  
         [0089]     The sequence diagram of  FIG. 8  shows processing in the case of service whose authentication level is high and which requires detailed information for authentication.  
         [0090]     The terminal  10 A transmits an access request to the communication control apparatus  20  (S 100 ). This access request contains information about the user of the terminal  10 A, information about the content of service for which the access request has been issued, and the like.  
         [0091]     The communication control apparatus  20  receives the access request through the I/F  21 . The communication program  231  receives this access request, analyzes the contents, thereof, and sends the request to the security/authentication level judgment program  233 . The security/authentication level judgment program  233  judges whether the access should be permitted with reference to the received contents of the access request (S 101 ).  
         [0092]     When the security/authentication level judgment program  233  has judged that it is impossible to approve the access request from the user and detailed information is required (S 109 ), the communication program  231  transmits a detailed information request to the terminal  10 A through the I/F  21  (S 110 ).  
         [0093]     Upon receiving this detailed information request approval, the terminal  10 A transmits an detailed information to the communication control apparatus  20  (S 111 ).  
         [0094]     Upon receiving this detailed information, the security/authentication level judgment program  233  of the communication control apparatus  20  refers to the contents of the detailed information and judges whether the access by the user should be permitted. Following this, when the access request from the user has been approved (S 112 ), the communication program  231  transmits a notification showing that the access request has been approved to the terminal  10 A through the I/F  21  (S 113 ).  
         [0095]     Upon receiving this access request approval, the terminal  10 A transmits this access request to the communication control apparatus  20  (S 114 ).  
         [0096]     Upon receiving the access request from the user of the terminal  10 A that has already been authenticated as eligible, the communication control apparatus  20  delivers a policy to the server  31 A of the service distributor  30 A (S 120 ). This policy contains information about the content of the service requested by the user, a notification showing that the user has already been authenticated as eligible, and the address of the terminal  10 A that issued the request. Upon receiving the policy, the server  31 A distributes the service to the terminal  10 A according to the contents of the policy (S 130 ).  
         [0097]      FIG. 9  is a flowchart of processing by the communication control apparatus  20 .  
         [0098]     The communication control apparatus  20  receives an access request from the terminal  10  (S 1001 ). This access request is sent to the communication program  231  through the I/F  21 . The communication program  231  analyzes the contents of the received access request and passes the access request to the security/authentication level judgment program  233 .  
         [0099]     The security/authentication level judgment program  233  acquires information about a user, who issued the access request, and information about a content from the received access request. Then, the security/authentication level judgment program  233  searches the user context information database  241  of the authentication database  240  and acquires information about the user. Also, the security/authentication level judgment program  233  searches the service content information database  242  of the authentication database  240  and acquires information about the content (S 1002 ).  
         [0100]     The security/authentication level judgment program  233  calculates a product of a value of a security level of the user and a value of a security level of the content. Then, the security/authentication level judgment program  233  selects an authentication method, which is suited for the access request, with reference to the calculated value and the judgment table  234  (S 1003 ).  
         [0101]     When the access request has been approved without performing authentication based on detailed information from the terminal  10 A (when the calculated value is “1”, for instance), a notification showing that the access request has been approved is transmitted to the terminal  10 A (S 1010 ).  
         [0102]     On the other hand, when it is impossible to approve the access request without performing authentication based on detailed information from the terminal  10 A (when the calculated value is “2” or more, for instance), in S 1003 , detailed information corresponding to the selected authentication scheme  2342  is requested. For instance, when the selected authentication scheme is “password input”, a registered user name and password are requested. Therefore, the communication control apparatus  20  transmits a detailed information request to the terminal  10 A (S 1004 ). More specifically, the security/authentication level judgment program  233  sends a detailed information request to the communication program  231 . The communication program  231  transmits the received detailed information request to the terminal  10 A through the I/F  21 .  
         [0103]     Upon receiving the detailed information request, the terminal  10 A transmits detailed information corresponding to the request to the communication control apparatus  20 . For instance, when the authentication scheme is “password input”, a program of the terminal  10 A prompts the user to input his/her user name and password. Upon receiving the input from the user, the terminal  10 A transmits the detailed information to the communication control apparatus  20 .  
         [0104]     The communication control apparatus  20  receives the detailed information from the terminal  10 A. This detailed information is sent to the communication program  231  through the I/F  21 . The communication program  231  analyzes the contents of the detailed information and sends the information to the security/authentication level judgment program  233 .  
         [0105]     Upon receiving the detailed information (S 1005 ), the security/authentication level judgment program  233  carries out authentication processing based on the information (S 1006 ). More specifically, the security/authentication level judgment program  233  authenticates the detailed information against information prestored in the database  24  based on the authentication scheme selected in step S 1003 .  
         [0106]     When having approved the access request, the security/authentication level judgment program  233  transmits a notification showing that the access request has been approved to the terminal  10 A (S 1007 ).  
         [0107]     When having approved the access request in step S 1007  or step S 1010 , the security/authentication level judgment program  233  registers the user authenticated as eligible and a corresponding authentication level in the user authentication processing information database  243  of the authentication database  240  (S 1008 ).  
         [0108]     Next, the security/authentication level judgment program  233  delivers a policy to the server  31  of the content provider  30 A that provides the content requested by the user of the terminal  10 A (S 1009 ). Upon receiving the policy, the server  31 A provides the terminal  10 A with the content of the service according to the contents of the policy.  
         [0109]      FIG. 10  is a flowchart of processing by the terminal  10 A.  
         [0110]     The terminal  10 A transmits an access request to the communication control apparatus  20  in order to receive distribution of the content of service requested by the user (S 1101 ).  
         [0111]     The terminal  10 A judges whether it has received an access request approval notification from the communication control apparatus  20  as a response to the access request (S 1102 ).  
         [0112]     When the terminal  10 A has received the access request approval notification, the requested service is distributed from the server  31 A of the service distributor  30 A and it becomes possible to use the service (S 1106 ).  
         [0113]     On the other hand, when it is impossible to approve the access request, the communication control apparatus  20  transmits a detailed information request. The terminal  10 A receives this detailed information request (S 1103 ). Then, the terminal  10 A transmits the detailed information corresponding to the request to the communication control apparatus  20  (S 1104 ). For instance, in the case of an authentication scheme “password input”, the program of the terminal  10 A prompts the user to input his/her user name and password. Then, the terminal  10 A receives the input by the user and transmits the detailed information to the communication control apparatus  20 .  
         [0114]     When the terminal  10 A has received the access request approval notification from the communication control apparatus  20  as a result of the transmission of the detailed information (S 1105 ), the requested service is distributed from the server  31 A of the service distributor  30 A and it becomes possible to use the service (S 1106 ).  
         [0115]     As described above, in the first embodiment of this invention, when requesting the service distributed by the service distributor  30 A, the terminal  10 A transmits an access request to the communication control apparatus  20 . The communication control apparatus  20  receives the access request and judges whether the terminal  10 A is permitted. When having authenticated the terminal  10 A as eligible, the communication control apparatus  20  issues a notification to the terminal  10 A and delivers a policy. to the service distributor  30 A. With this construction, it becomes possible for the terminals  10  to use the content of the service distributed by the service distributors  30  only by performing authentication processing with respect to the communication control apparatus  20 . As a result, it becomes unnecessary for the terminals  10  to issue authentication requests to the respective service distributors.  
       Second Embodiment  
       [0116]     Next, a distributed authentication system according to a second embodiment of this invention will be described.  
         [0117]      FIG. 11  is a construction diagram of the distributed authentication system according to the second embodiment of this invention.  
         [0118]     In the distributed authentication system of this embodiment, a terminal  10 , communication control apparatuses  20  ( 20 A and  20 B), and a server  31  of a service distributor  30  are connected to each other through a network.  
         [0119]     It should be noted that the terminal  10 , the communication control apparatuses  20  ( 20 A and  20 B), and the server  31  of the service distributor  30  are the same as those of the first embodiment described above, so the description thereof will be omitted.  
         [0120]     Also, the terminal  10  is constructed so that it is movable and is capable of connecting to and communicating with each of the communication control apparatuses  20 A and  20 B.  
         [0121]     An operation of the distributed authentication system of the second embodiment will be described.  
         [0122]     Processing in the case where the terminal  10  requests the content of service distributed from the server  31  of the service distributor  30  is the same as that of the first embodiment described above.  
         [0123]     In other words, the terminal  10  transmits an access request to the communication control apparatus  20 A (S 100 ). This access request contains information about the terminal  10 , information about a user of the terminal, and information about the requested content. Upon receiving the access request from the terminal  10 , the communication control apparatus  20 A performs authentication processing based on the information about the terminal, the information about the user, and the information about the content of the service contained in the request. When having authenticated the terminal  10  as eligible, the communication control apparatus  20 A delivers a policy to the server  31  of the service distributor  30  (S 120 ). Upon receiving the delivered policy, the server  31  distributes the content of the service to the terminal  10  (S 130 ).  
         [0124]     On the other hand, when it is impossible to authenticate the terminal  10  as eligible only with the information contained in the access request from the terminal  10 , the communication processing apparatus  20 A requests the terminal  10  to further transmit detailed information (S 110 ). Upon receiving this request for the detailed information transmission, the terminal  10  transmits the detailed information to the communication processing terminal  20 . Upon receiving the detailed information from the terminal  10 , the communication processing terminal  20 A performs authentication processing based on information contained in the detailed information. When having authenticated the terminal  10  as eligible, the communication control apparatus  20 A delivers a policy to the server  31  of the service distributor  30  (S 120 ). Upon receiving the delivered policy, the server  31  distributes the content of the service to the terminal  10  (S 130 ).  
         [0125]     Also, when having. approved the access request from the terminal  10 , the communication control apparatus  20 A registers the user of the terminal  10  in a user authentication processing information database  243  of an authentication database. This user authentication processing information database  243  is synchronized with that of the other communication control apparatus  20 B. In other words, the contents of the user authentication processing information database  243  registered in the communication control apparatus  20 A are transmitted to the communication control apparatus  20 B and the contents of the user authentication processing information database  243  of the communication control apparatus  20 A and those of the communication control apparatus  20 B are set identical to each other (S 200 ). In this case, an encryption/decryption program  232  encrypts the user authentication processing information and the encrypted information is transmitted to the information control apparatus  20 B. Then, an encryption/decryption program  232  of the information control apparatus  20 B decrypts the encrypted information.  
         [0126]     Next, a case where the terminal  10  has moved to be connected to the communication control apparatus  20 B will be described.  
         [0127]     After having connected to the communication control apparatus  20 B, the terminal  10  transmits an access request to the communication control apparatus  20 B (S 210 ).  
         [0128]     The communication control apparatus  20 B receives the access request and judges whether the terminal  10  should be authenticated as eligible with reference to the received access request and the user authentication processing information.  
         [0129]     The user authentication processing information database  243  of the communication control apparatus  20 A and that of the communication control apparatus  20 B have been set identical to each other. When information showing that the terminal  10  that transmitted the access request has already been authenticated as eligible by the communication control apparatus  20 A is stored in the user authentication processing information  243  of the communication control apparatus  20 B, the communication control apparatus  20 B authenticates the terminal  10  as eligible. When having authenticated the terminal  10  as eligible, the communication control apparatus  20 B delivers a policy to the server  31  of the service distributor  30  (S 230 ). Upon receiving the delivered policy, the server  31  distributes the content of the service to the terminal  10  (S 240 ).  
         [0130]     Next, an operation of the distributed authentication system of this embodiment will be described.  
         [0131]      FIG. 12  is a sequence diagram of authentication processing according to this embodiment.  
         [0132]     The sequence diagram of  FIG. 12  shows processing in the case of service whose authentication level is low and which the user is capable of accessing without performing authentication.  
         [0133]     The terminal  10  transmits an access request to the communication control apparatus  20 A (S 100 ). This access request contains information about the user of the terminal  10 , information about the content of service for which the access request has been issued, information showing previous and current positions of the terminal  10 , information showing whether the terminal  10  has already been authenticated, and the like.  
         [0134]     The communication control apparatus  20 A receives the access request through the I/F  21 . The communication program  231  receives this access request, analyzes the contents thereof, and sends the request to the security/authentication level judgment program  233 . The security/authentication level judgment program  233  judges whether the access should be permitted with reference to the contents of the access request (S 101 ).  
         [0135]     When the security/authentication level judgment program  233  has judged to approve the access request from the user without requesting additional information (S 102 ), the communication program  231  transmits a notification showing that the access request has been approved to the terminal  10  through the I/F  21  (S 103 ).  
         [0136]     Upon receiving this access request approval, the terminal  10  transmits an access request to the communication control apparatus  20 A (S 104 ).  
         [0137]     Also, when having approved the access request from the terminal  10 , the communication control apparatus  20 A registers the user of the terminal  10  in the user authentication processing information database  243  of the authentication database. This user authentication processing information database  243  is synchronized with that of the other communication control apparatus  20 B. In other words, the contents of the user authentication processing information database  243  registered in the communication control apparatus  20 A are transmitted to the communication control apparatus  20 B and the contents of the user authentication processing information database  243  of the communication control apparatus  20 A and those of the communication control apparatus  20 B are set identical to each other (S 200 ).  
         [0138]     Upon receiving the access request from the user of the terminal  10  that has already been authenticated as eligible, the communication control apparatus  20 A delivers a policy to the server  31  of the service distributor  30  (S 120 ). This policy contains information about the content of the service requested by the user, a notification showing that the user has already been authenticated as eligible, and the address of the terminal  10  that issued the request.  
         [0139]     Upon receiving the policy, the server  31  of the service distributor  30  distributes the service to the terminal  10  according to the contents of the policy (S 130 ).  
         [0140]     Next, when having moved to be connected to the communication control apparatus  20 B, the terminal  10  transmits an access request to the communication control apparatus  20 B (S 210 ). This access request contains information showing previous and present positions of the terminal  10 , information showing whether the terminal  10  has already been authenticated as eligible, and the like in addition to the information contained in the access request issued in step S 100  described above.  
         [0141]     The communication control apparatus  20 B receives the access request through the I/F  21 . The communication program  231  receives this, access request, analyzes the contents thereof, and sends the request to the security/authentication level judgment program  233 . The security/authentication level judgment program  233  judges whether the access should be permitted with reference to the contents of the access request (S 211 ).  
         [0142]     The security/authentication level judgment program  233  refers to the synchronized user authentication processing information database  243 . When judging that the user has already been authenticated as eligible, the security/authentication level judgment program  233  approves the access request (S 212 ). Then, the communication program  231  transmits a notification showing that the access request has been approved to the terminal  10  through the I/F  21  (S 213 ).  
         [0143]     Upon receiving this access request approval, the terminal  10  transmits an access request to the communication control apparatus  20 B (S 214 ).  
         [0144]     Upon receiving the access request from the user of the terminal  10 , the communication control apparatus  20 B delivers a policy to the server  31  of the service distributor  30  (S 230 ). This policy contains information about the content of the service requested by the user, a notification showing that the user has already been authenticated as eligible, and the address of the terminal  10  that issued the request. Upon receiving the policy, the server  31  distributes the service to the terminal  10  according to the contents of the policy (S 240 ).  
         [0145]      FIG. 13  is another sequence diagram of the authentication processing according to this embodiment.  
         [0146]     Processing shown in  FIG. 13  is processing in the case where when the terminal  10  has moved and transmitted an access request to the communication control apparatus  20 B, the contents of the user authentication processing information database  243  of the communication control apparatus  20 B have not yet been synchronized with those of the communication control apparatus  20 A.  
         [0147]     When having moved to be connected to the communication control apparatus  20 B, the terminal  10  transmits an access request to the communication control apparatus  20 B (S 210 ). This access request contains information showing previous and present positions of the terminal  10 , information showing whether the terminal  10  has already been authenticated as eligible, and the like in addition to the information contained in the access request issued in step S 100  described above.  
         [0148]     The communication control apparatus  20 B receives the access request through the I/F  21 . The communication program  231  receives this access request, analyzes the contents thereof, and sends the request to the security/authentication level judgment program  233 .  
         [0149]     The security/authentication level judgment program  233  first refers to the user authentication processing information database  243 . When having judged that information about authentication of the user is not registered in the user authentication processing information database  243 , the security/authentication level judgment program  233  refers to the position information contained in the received access request and acquires information about the communication control apparatus  20 A in which authentication processing information has been registered at an immediately preceding position of the terminal  10 . Then, the security/authentication level judgment program  233  inquires of the communication control apparatus  20 A about the user authentication processing information (S 215 ). This inquiry contains information about the user of the terminal  10  that issued the access request.  
         [0150]     Upon receiving the authentication processing information inquiry from the communication control apparatus  20 B, the communication control apparatus  20 A acquires authentication processing information corresponding to the user information contained in the inquiry from the user authentication processing information database  243  of the authentication database  240 . Then, the communication control apparatus  20 A transmits the acquired authentication processing information to the communication control apparatus  20 B (S 216 ).  
         [0151]     The communication control apparatus  20 B receives the authentication processing information through the I/F  21 . The communication program  231  receives this authentication processing information, analyzes the contents thereof, and transmits the information to the security/authentication level judgment program  233 . The security/authentication level judgment program  233  refers to the authentication processing information and approves the access request without requesting additional information (S 217 ). The communication program  231  transmits a notification showing that the access request has been approved to the terminal  10  through the I/F  21  (S 218 ).  
         [0152]     Upon receiving this access request approval, the terminal  10  transmits an access request to the communication control apparatus  20 A (S 219 ).  
         [0153]     Upon receiving the access request from the user of the terminal  10  that has already been authenticated as eligible, the communication control apparatus  20 B delivers a policy to the server  31  of the service distributor  30  (S 230 ). This policy contains information about the content of the service requested by the user, a notification showing that the user has already been authenticated as eligible, and the address of the terminal  10  that issued the request.  
         [0154]     Upon receiving the policy, the server  31  of the service distributor  30  distributes the service to the terminal  10  according to the contents of the policy (S 240 ).  
         [0155]     It should be noted that, instead of transmitting the position information, the terminal  10  may transmit information about a communication control apparatus at which the terminal  10  was authenticated as eligible in the past (S 210 ). Upon receiving this access request, the communication control apparatus  20 B acquires the information about the communication control apparatus contained in the access request and inquires of the communication control apparatus about information on the authentication of the terminal that issued the request.  
         [0156]      FIG. 14  is a flowchart of processing by the communication control apparatus  20 B.  
         [0157]     The communication control apparatus  20 B receives an access request from the terminal  10  (S 2001 ). This access request is sent to the communication program  231  through the I/F  21 . The communication program  231  analyzes the contents of the access request and passes the request to the security/authentication level judgment program  233 .  
         [0158]     The security/authentication level judgment program  233  acquires information about a user, who issued the access request, and information about a content from the access request. Then, the security/authentication level judgment program  233  searches the user context information database  241  of the authentication database  240  and acquires information about the user. Also, the security/authentication level judgment program  233  searches the service content information database  242  of the authentication database  240  and acquires information about the content (S 2002 ).  
         [0159]     Next, the security/authentication level judgment program  233  judges whether the user of the terminal  10  that issued the access request has already been authenticated as eligible (S 2002 ).  
         [0160]     More specifically, first, the security/authentication level judgment program  233  judges whether the user of the terminal  10  that issued the access request has already been authenticated as eligible with reference to the user authentication processing information database  243  of the authentication database  240 .  
         [0161]     Also, when information about authentication processing of the user is not stored in the user authentication processing information database  243 , the security/authentication level judgment program  233  refers to the position information contained in the received access request and acquires information about the communication control apparatus  20 A in which information about authentication processing of the terminal  10  has been registered at an immediately preceding position. Then, the security/authentication level judgment program  233  inquires of the communication control apparatus  20 A about the information on the authentication processing of the user. This inquiry contains information about the user of the terminal  10  that issued the access request.  
         [0162]     The communication control apparatus  20 B receives the authentication processing information from the communication control apparatus  20 A through the I/F  21 . The communication program  231  receives this authentication processing information, analyzes the contents thereof, and transmits the information to the security/authentication level judgment program  233 . The security/authentication level judgment program  233  judges whether the user of the terminal  10  that issued the access request has already been authenticated as eligible with reference to the authentication processing information.  
         [0163]     When having judged that the user of the terminal  10  that issued the access request has already been authenticated as eligible, the security/authentication level judgment program  233  approves the access request without performing authentication based on detailed information from the terminal  10 . Then, a notification showing that the access request has been approved is transmitted to the terminal  10  (S 2011 ). On the other hand, when it has been judged that the user of the terminal  10  that issued the access request has not yet been authenticated as eligible, the processing proceeds to step S 2004 .  
         [0164]     The security/authentication level judgment program  233  calculates a product of a value of a security level of the user and a value of a security level of the content. Then, the security/authentication level judgment program  233  selects an authentication method, which is suited for the access request, with reference to the calculated value and the judgment table  234  (S 2004 ).  
         [0165]     When the access request has been approved with the selected authentication method without performing authentication based on detailed information from the terminal  10  (when the calculated value is “1”, for instance), a notification showing that the access request has been approved is transmitted to the terminal  10  (S 2011 ).  
         [0166]     On the other hand, when it is impossible to approve the access request with the selected authentication method without performing authentication based on detailed information from the terminal  10  (when the calculated value is “2” or more, for instance), detailed information corresponding to the selected authentication scheme  2342  is requested (S 2005 ). For instance, when the selected authentication scheme is “password input”, a registered user name and password are requested. Therefore, the communication control apparatus  20  transmits a detailed information request to the terminal  10  (S 2005 ). More specifically, the security/authentication level judgment program  233  sends a detailed information request to the communication program  231 . The communication program  231  transmits the received detailed information request to the terminal  10  through the I/F  21 .  
         [0167]     Upon receiving the detailed information request, the terminal  10  transmits detailed information corresponding to the request to the communication control apparatus  20 . For instance, when the selected authentication scheme is “password input”, a program of the terminal  10  prompts the user to input his/her user name and password. Upon receiving the input from the user, the terminal  10  transmits the detailed information to the communication control apparatus  20 .  
         [0168]     The communication control apparatus  20  receives the detailed information from the terminal  10 . This detailed information is sent to the communication program  231  through the I/F  21 . The communication program  231  analyzes the contents of the received detailed information and sends the information to the security/authentication level judgment program  233 .  
         [0169]     Upon receiving the detailed information (S 2006 ), the security/authentication level judgment program  233  carries out authentication processing based on the information (S 2007 ). More specifically, the security/authentication level judgment program  233  authenticates the user of the terminal  10  by checking the detailed information against information prestored in the database  24  based on the authentication scheme selected in step S 2004 .  
         [0170]     When having approved the access request, the security/authentication level judgment program  233  transmits a notification showing that the access request has been approved to the terminal  10  (S 2008 ).  
         [0171]     After having transmitted the access request approval notification in step S 2008  or step S 2011 , the security/authentication level judgment program  233  registers the user authenticated as eligible and a corresponding authentication level in the user authentication processing information database  243  of the authentication database  240  (S 2009 ).  
         [0172]     Next, the security/authentication level judgment program  233  delivers a policy to the server  31  of the content provider  30  that provides the content requested by the user of the terminal  10  (S 2010 ). Upon receiving the policy, the server  31  provides the terminal  10  with the content of the service according to the contents of the policy.  
         [0173]     As described above, in the second embodiment of this invention, the user authentication processing information of a plurality of communication control apparatuses  20  is set identical to each other through synchronization, so even when the terminal  10  of the user has moved, it becomes possible for the user to receive the service from the service distributor without performing authentication again. Also, when information showing that the user has already been authenticated as eligible is not stored in the communication control apparatus  20  to which the terminal  10  has moved to be connected, the communication control apparatus  20  finds the communication control apparatus  20 , with which the terminal  10  communicated in the past, based on information showing a previous position of the terminal  10  and inquires of the found communication control apparatus  20  about authentication processing information, so even when the terminal  10  has moved, it becomes possible for the user to receive the service provided by the service distributor without performing authentication again in a like manner.  
         [0174]     It should be noted that time information may be given to the information stored in the user authentication processing information database  243 . In this case, when an access request is received from the terminal  10  again, when a predetermined time has passed from previous authentication, authentication processing is requested again. By setting a term of validity for authentication in this manner, it becomes possible to further enhance security of the authentication.  
       Third Embodiment  
       [0175]     Next, a distributed authentication system according to a third embodiment of this invention will be described.  
         [0176]      FIG. 15  is a construction diagram of the distributed authentication system according to the third embodiment of this invention.  
         [0177]     In the distributed authentication system of this embodiment, a terminal  10  ( 10 A to  10 N), communication control apparatuses  20  and a service distributor  30  are connected to each other through a network.  
         [0178]     It should be noted that the terminal  10  ( 10 A to  10 N), the communication control apparatuses  20  and the service distributor  30  are the same as those of the first embodiment described above, so the description thereof will be omitted.  
         [0179]     Also, a server  31  of the service distributor  30  is constructed so that it is capable of distributing service to the plurality of terminals  10 A to  10 N at the same time using a broadcast or multicast technique.  
         [0180]     The server  31  of the service distributor  30  transmits a distribution request to the communication control apparatus  20  (S 300 ). This distribution request contains information about the terminals  10  that are distribution destinations, information about users of the terminals  10 , and information about a content to be distributed.  
         [0181]     Upon receiving the distribution request from the service distributor  30 , the communication control apparatus  20  performs authentication processing based on the information about the terminals, the information about the users, and the information about the content of the service contained in the distribution request. When having permitted the distribution to the terminals  10  designated by the request, the communication control apparatus  20  transmits a notification showing that the distribution has been permitted to the server  31  of the service distributor  30  (S 310 ). Upon receiving this distribution permission notification, the server  31  of the service distributor  30  distributes the content of the service to the terminals  10  (S 320 ).  
         [0182]     On the other hand, when it is impossible to permit the distribution only with the information contained in the distribution request, the communication processing apparatus  20  requests the server  31  of the service distributor  30  to further transmit detailed information.  
         [0183]     Upon receiving this detailed information transmission request, the server  31  of the service distributor  30  transmits detailed information to the communication processing terminal  20 . Upon receiving the detailed information, the communication processing terminal  20  performs authentication processing based on information contained in the detailed information. When having permitted the distribution to the terminals  10  designated by the request, the communication control apparatus  20  transmits a notification showing that the distribution has been permitted to the server  31  of the service distributor  30  (S 310 ). Upon receiving this distribution permission notification, the server  31  of the service distributor  30  distributes the content of the service to the terminals  10  (S 320 ).  
         [0184]     Next, an operation of the distributed authentication system according to this embodiment will be described.  
         [0185]      FIG. 16  is a sequence diagram of authentication processing according to this embodiment.  
         [0186]     The sequence diagram of  FIG. 16  shows processing in the case of service whose authentication level is low and which the user is capable of accessing without performing authentication.  
         [0187]     The server  31  of the service distributor  30  transmits a distribution request to the communication control apparatus  20  (S 300 ). This distribution request contains information about the terminal  10  serving as a distribution destination, information about the user of the terminal  10 , information about the content of service for which the access request has been issued, and the like.  
         [0188]     The communication control apparatus  20  receives the distribution request through the I/F  21 . The communication program  231  receives this distribution request, analyzes the contents thereof, and sends the request to the security/authentication level judgment program  233 . The security/authentication level judgment program  233  judges whether the access should be permitted with reference to the contents of the distribution request (S 301 ).  
         [0189]     When the security/authentication level judgment program  233  has approved the distribution request of the terminal  10  distribution information without requesting additional information (S 302 ), the communication program  231  transmits a notification showing that the distribution request has been approved to the server  31  of the service distributor  30  through the I/F  21  (S 310 ).  
         [0190]     Upon receiving this permission, the server  31  of the service distributor  30  distributes the service to the terminals  10  designated by the distribution request (S 320 ).  
         [0191]      FIG. 17  is another sequence diagram of the authentication processing according to this embodiment.  
         [0192]     The sequence diagram of  FIG. 17  shows processing in the case of service whose authentication level is high and which requires detailed information for authentication.  
         [0193]     The server  31  of the service distributor  30  transmits a distribution request to the communication control apparatus  20  (S 300 ). This distribution request contains information about the terminal  10  serving as a distribution destination, information about the user of the terminal  10 , information about the content of service for which the access request has been issued, and the like.  
         [0194]     The communication control apparatus  20  receives the distribution request through the I/F  21 . The communication program  231  receives this distribution request, analyzes the contents thereof, and sends the request to the security/authentication level judgment program  233 . The security/authentication level judgment program  233  judges whether the access should be permitted with reference to the contents of the distribution request (S 301 ).  
         [0195]     When the security/authentication level judgment program  233  has decided that the terminals  10  designated by the distribution request are prohibited (S 302 ), the communication program  231  transmits a detailed information request to the server  31  of the service distributor  30  through the I/F  21  (S 310 ).  
         [0196]     Upon receiving this detailed information request, the server  31  of the service distributor  30  transmits the detailed information to the communication control apparatus  20  (S 311 ).  
         [0197]     Upon receiving this detailed information, the security/authentication level judgment program  233  of the communication control apparatus  20  authenticates the terminals  10  designated by the distribution request again with reference to the contents of the detailed information.  
         [0198]     When the security/authentication level judgment program  233  has authenticated the terminals  10  designated by the distribution request as eligible (S 312 ), the communication program  231  transmits a notification showing that the distribution has been permitted to the server  31  of the service distributor  30  through the I/F  21  (S 313 ).  
         [0199]     Upon receiving this permission, the server  31  of the service distributor  30  distributes the service to the terminals  10  designated by the distribution request (S 320 ).  
         [0200]     As described above, in the third embodiment of this invention, when a service distributor  30  side distributes service to the terminals, it transmits a distribution request to the communication control apparatus  20 . The communication control apparatus  20  authenticates this distribution request, so the service from the service distributor  30  to the terminals  10  can be permitted. It should be noted that authentication processing performed to judge whether the distribution should be permitted is approximately the same as that of the first embodiment.  
       Fourth Embodiment  
       [0201]     Next, a distributed authentication system according to a fourth embodiment of this invention will be described.  
         [0202]      FIG. 18  is a construction diagram of the distributed authentication system according to the fourth embodiment of this invention.  
         [0203]     In the distributed authentication system of this embodiment, a terminal  10 , communication control apparatuses  20  ( 20 A and  20 B), and a server  31  of a service distributor  30  are connected to each other through a network.  
         [0204]     It should be noted that the terminal  10 , the communication control apparatuses  20  ( 20 A and  20 B), and the server  31  of the service distributor  30  are the same as those of the first embodiment described above, so the description thereof will be omitted.  
         [0205]     Also, the terminal  10  is constructed so that it is movable and is capable of connecting to and communicating with each of the communication control apparatuses  20 A and  20 B.  
         [0206]     An operation of the distributed authentication system according to the fourth embodiment will be described.  
         [0207]     Processing in the case where the service distributor  30  requests service distribution is the same as that of the third embodiment described above.  
         [0208]     In other words, the server  31  of the service distributor  30  transmits a distribution request to the communication control apparatus  20 A (S 400 ). This distribution request contains information about the terminals  10  that are distribution destinations, information about users of the terminals  10 , and information about a content to be distributed.  
         [0209]     Upon receiving the distribution request from the server  31 , the communication control apparatus  20 A performs authentication processing based on the information about the terminals, the information about the users, and the information about the content of the service contained in the distribution request. When having permitted the distribution to the terminals  10  designated by the request, the communication control apparatus  20 A transmits a notification showing that the distribution has been permitted to the server  31  of the service distributor  30  (S 410 ). Upon receiving this distribution permission notification, the server  31  of the service distributor  30  distributes the content of the service to the terminals  10  (S 420 ).  
         [0210]     On the other hand, when it is impossible to permit the distribution only with the information contained in the distribution request, the communication processing apparatus  20 A requests the server  31  of the service distributor  30  to further transmit detailed information (S 410 ).  
         [0211]     Upon receiving this detailed information transmission request, the server  31  of the service distributor  30  transmits the detailed information to the communication processing terminal  20 . Upon receiving the detailed information, the communication processing terminal  20 A performs authentication processing based on information contained in the detailed information. When having permitted the distribution to the terminals  10  designated by the request, the communication control apparatus  20 A transmits a notification showing that the distribution has been permitted to the server  31  of the service distributor  30 . Upon receiving this distribution permission notification, the server  31  distributes the content of the service to the terminals  10  (S 420 ).  
         [0212]     Next, a case where the terminal  10  has moved to be connected to the communication control apparatus  20 B will be described.  
         [0213]     After having connected to the communication control apparatus  20 A, the server  31  of the service distributor  30  transmits a distribution request to the communication control apparatus  20 A, in a like manner (S 400 ).  
         [0214]     The communication control apparatus  20 A receives the distribution request and judges whether the terminal  10  should be authenticated as eligible with reference to the received distribution request and the user authentication processing information.  
         [0215]     The terminal  10  designated by the distribution request does not currently connect to the communication control apparatus  20 A. Therefore, the security/authentication level judgment program  233  inquires of the communication control apparatus  20 B, to which the terminal  10  currently connects, about user authentication processing information (S 500 ).  
         [0216]     Upon receiving the authentication processing information inquiry from the communication control apparatus  20 A, the communication control apparatus  20 B acquires authentication processing information corresponding to the user information contained in the inquiry from the user authentication processing information database  243  of the authentication database  240 . Then, the communication control apparatus  20 B transmits the acquired authentication processing information to the communication control apparatus  20 A (S 510 ).  
         [0217]     Upon receiving the distribution request from the service distributor  30 , is processed based on the information about the terminal, the information about the user, and information about the content of the service contained in the distribution request. When having permitted the distribution to the terminal  10  designated by the request transmission of a notification showing that the distribution has been permitted to the server  31  of the service distributor  30  is sent (S 430 ). Upon receiving this distribution permission notification, the server  31  distributes the content of the service to the terminal  10  (S 440 ).  
         [0218]     Next, an operation of the distributed authentication system according to this embodiment will be described.  
         [0219]      FIG. 19  is a sequence diagram of authentication processing according to this embodiment.  
         [0220]     The sequence diagram of  FIG. 19  shows processing in the case of service whose authentication level is low and which the user is capable of accessing without performing authentication.  
         [0221]     The server  31  of the service distributor  30  transmits a distribution request to the communication control apparatus  20  (S 400 ). This distribution request contains information about the terminal  10  serving as a distribution destination, information about the user of the terminal  10 , information about the content of service for which the access request has been issued, and the like.  
         [0222]     The communication control apparatus  20  receives the distribution request through the I/F  21 . The communication program  231  receives this distribution request, analyzes the contents thereof, and sends the request to the security/authentication level judgment program  233 . The security/authentication level judgment program  233  judges whether the access should be permitted with reference to the contents of the distribution request (S 401 ).  
         [0223]     When the security/authentication level judgment program  233  has approved the distribution request of the terminal  10  distribution information without requesting additional information (S 402 ), the communication program  231  transmits a notification showing that the distribution request has been approved to the server  31  of the service distributor  30  through the I/F  21  (S 403 ).  
         [0224]     Upon receiving this permission, the server  31  of the service distributor  30  distributes the service to the terminals  10  designated by the distribution request (S 420 ).  
         [0225]     Next, a case where the terminal  10  has moved to be connected to the communication control apparatus  20 B will be described.  
         [0226]     The server  31  of the service distributor  30  transmits a distribution request to the communication control apparatus  20 A (S 450 ).  
         [0227]     The communication control apparatus  20 A receives the distribution request through the I/F  21 . The communication program  231  receives this distribution request, analyzes the contents thereof, and sends the request to the security/authentication level judgment program  233 . The security/authentication level judgment program  233  is executed with reference to the contents of the distribution request (S 404 ).  
         [0228]     The terminal  10  designated by the distribution request does not currently connect to the communication control apparatus  20 A. Therefore, the security/authentication level judgment program  233  inquires of the communication control apparatus  20 B, to which the terminal  10  currently connects, about user authentication processing information (S 500 ). This inquiry contains information about the user of the terminal  10  designated by the distribution request.  
         [0229]     Upon receiving the authentication processing information inquiry from the communication control apparatus  20 A, the communication control apparatus  20 B acquires authentication processing information corresponding to the user information contained in the inquiry from the user authentication processing information database  243  of the authentication database  240 . Then, the communication control apparatus  20 B transmits the acquired authentication processing information to the communication control apparatus  20 A (S 510 ).  
         [0230]     The communication control apparatus  20 B receives the authentication processing information through the I/F  21 . The communication program  231  receives this authentication processing information, analyzes the contents thereof, and transmits the information to the security/authentication level judgment program  233 . The security/authentication level judgment program  233  transmits the distribution request transmitted from the server  31  of the service distributor  30  to the communication control apparatus  20 B with reference to the authentication processing information. In other words, the communication program  231  of the communication control apparatus  20 A transmits the distribution request to the communication control apparatus  20 B through the I/F  21  (S 511 ).  
         [0231]     Upon receiving the distribution request from the server  31 , the security/authentication level judgment program  233  of the communication control apparatus  20 A performs authentication processing based on the information about the terminal, the information about the user, and the information about the content of the service contained in the distribution request (S 512 ). When having permitted the distribution to the terminal  10  designated by the request (S 513 ), the security/authentication level judgment program  233  transmits a notification showing that the distribution has been permitted to the server  31  of the service distributor  30  (S 430 ). Upon receiving this distribution permission notification, the server  31  distributes the content of the service to the terminal  10  (S 440 ).  
         [0232]     As described above, in the fourth embodiment of this invention, the user authentication processing information in a plurality of communication control apparatuses  20  is set identical to each other through synchronization, so when the service distributor  30  distributes the service to the terminal  10 , even when the terminal  10  has moved, it becomes possible for the service distributor  30  to distribute the service without performing authentication again. Also, when the terminal  10  has moved, the communication control apparatus  20 , to which the terminal  10  currently connects, is found and an authentication processing information inquiry is made to the found communication control apparatus  20 , so even when the terminal  10  has moved, it becomes possible for the service distributor  30  to distribute the service without performing authentication again in a like manner.  
       Fifth Embodiment  
       [0233]     Next, a distributed authentication system in a fifth embodiment of this invention will be described.  
         [0234]      FIG. 20  is a construction diagram of the distributed authentication system according to the fifth embodiment of this invention.  
         [0235]     It is required that the user context information  241  stored in the authentication database  240  of the communication control apparatus  20  is registered in advance before authentication processing is performed.  
         [0236]     Therefore, a Web server  40  and a management server  50  are provided in the distributed authentication system.  
         [0237]     The Web server  40  includes a program and provides a terminal  10  that accesses the Web server  40  with a Web page. The management server  50  includes a program, acquires user context information registered by the terminal  10 , and registers the acquired user context information in the communication control apparatus  20 .  
         [0238]     More specifically, the terminal  10  accesses the Web server  40  with reference to an address of the server  40 . Then, the terminal  10  receives a portal site provided by the Web server  40  and displays the site. Next, a user operating the terminal  10  inputs his/her user context information according to instructions on the displayed portal site. Examples of the inputted user context information include the name, address, age, use history, and security information of the user.  
         [0239]     When the user has inputted the user context information into the portal site provided by the Web server  40  and has issued a registration instruction, a notification is sent to the management server.  
         [0240]     The management server  50  acquires the user context information inputted to the portal site provided by the Web server  40  and transmits the information to the communication control apparatus  20 . The communication control apparatus  20  registers the user context information in the user context information database  241  of the authentication database  240 .  
         [0241]      FIG. 21  is another construction diagram of the distributed authentication system according to the fifth embodiment of this invention.  
         [0242]     In this drawing, instead of providing the functions of the Web server  40  and the management server  50  as independent servers, a Web server program  41  having the function of the Web server  40  and a management server program  51  having the function of the management server  50  are stored in the communication control apparatus  20 .  
         [0243]     As described above, the terminal  10  accesses a portal site provided by the Web server program  41  of the communication control apparatus  20  and the user inputs his/her user context information. When the user has inputted the user context information into the portal site provided by the Web server program  41  and has issued a registration instruction, a notification is sent to the management server program  51 .  
         [0244]     The management server program  51  acquires the user context information inputted in the portal site provided by the Web server program  41  and registers the information in the user context information database  241  of the authentication database  240 .  
         [0245]     As described above, in the fifth embodiment of this invention, it becomes possible to register the user context information in the communication control apparatus  20  through operations from the terminal  10 .  
         [0246]     It should be noted that a construction may be used instead in which the user context information is registered not by the user operating the terminal  10  but by an administrator at the service distributor  30 .  
         [0247]     While the present invention has been described in detail and pictorially in the accompanying drawings, the present invention is not limited to such detail but covers various obvious modifications and equivalent arrangements, which fall within the purview of the appended claims.