Abstract:
Both a management server and a validation server are installed. Both a terminal and a terminal register setting information which is usable in an encrypted communication in the management server. When carrying out the encrypted communication, the management server searches the registered setting information for coincident setting information. The management server generates keys for the encrypted communications which can be used by the terminals, and delivers these generated keys in combination with the coincident setting information. The management server authenticates both the terminals in conjunction with the validation server. Since the terminals trust such results that the management server has authenticated the terminals respectively, these terminals need not authenticate the respective communication counter terminals.

Description:
INCORPORATION BY REFERENCE 
       [0001]    This application is a Continuation of U.S. application Ser. No. 10/931,219, filed Sep. 1, 2004, claiming priority based on a Japanese patent application, No. 2004-113732 filed on Apr. 8, 2004, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present invention is related to a method for allocating keys used in encrypted communications to both a communication source terminal and a communication destination terminal, and also related to a key allocation system. 
         [0003]    In the case that both a communication source apparatus and a communication destination apparatus (will be simply referred to as “terminals” hereinafter) perform an encrypted communication via a network, data of the communication is encrypted and then the encrypted data is transmitted/received. While both the communication source terminal and the communication destination terminal have previously and commonly owned both setting information and keys which are used in an encrypted communication between the communication source terminal and the communication destination terminal, the communication source terminal is encryption-communicated with the communication destination terminal by employing the setting information and the keys, which are commonly owned. 
         [0004]    For instance, in a case that a key is shared by employing public key encryption, the below-mentioned encrypted communication will be carried out. 
         [0005]    That is, a communication source terminal acquires a public key of a communication destination terminal, produces a key which is used so as to perform an encrypted communication with the communication destination terminal, and encrypts this key used for the encrypted communication by employing this public key, and then, transmits the encrypted key to the communication destination terminal. Also, the communication destination terminal receives the key used for the encrypted communication, which has been encrypted by this public key of the communication destination terminal, and then, decrypts the received encrypted key based upon a private key of the communication destination terminal. 
         [0006]    In the above-explained method, in order that the communication source terminal executes encrypted communications with respect to plural communication destination terminals, this communication source terminal and the respective communication destination terminals must commonly own the setting information and the keys used for the encrypted communications. Therefore, there is such a problem that loads of the communication source terminal are increased. 
         [0007]    As a consequence, the below-mentioned encrypted communication technique has been proposed. That is, while a server apparatus (will be referred to as “server” hereinafter) which allocates both the setting information and the key for the encrypted communication to both a communication source terminal and a communication destination terminal is installed on a network, both the communication source terminal and the communication destination terminal execute an encrypted communication by employing the above-described setting information and keys for the encrypted communication. Mark Baugher et. al., “MSEC Group Key Management Architecture &lt;draft-ietf-msec-gkmarch-07.txt&gt;”, Jan. 30, 2003, IETF (Internet Engineering Task Force) pages 3 to 13, refer to: &lt;URL: http://www.ietf.org/internet-drafts/draft-ietf-msec-gkmarch-07.txt&gt;. 
         [0008]    Also, in order that a validity of a communication counter party is confirmed in a communicating operation established via a network, the communication counter party must be authenticated before the communicating operation is carried out. As one of methods for authenticating communication counter parties, such an authenticating method with employment of an electronic signature is provided. Concretely speaking, both a communication source terminal and a communication destination terminal, which are communicated to each other, exchange IDs and public key s, to which electronic signatures have been applied. Then, both the communication source terminal and the communication destination terminal verify both the received electronic signatures and the received public key s so as to authenticate the communication counter parties with each other. 
       SUMMARY OF THE INVENTION 
       [0009]    In order that a communication source terminal executes encrypted communications with respect to a plurality of communication destination terminals, this communication source terminal and the respective communication destination terminals must commonly own setting information and keys used for this encrypted communication, so that loads given to the communication source terminal are increased. 
         [0010]    For instance, in order that a communication source terminal commonly owns keys used for an encrypted communication with respect to a communication destination terminal by employing a public key encryption, the communication source terminal must perform the following process operations, namely, the communication source terminal acquires a public key of the communication destination terminal, produces a key which is used so as to perform the encrypted communication with the communication destination terminal, and encrypts this key used for the encrypted communication by employing the acquired public key, so that loads given to the communication source terminal are increased. 
         [0011]    To solve this problem, in such a case that the technique of the above-explained non-patent publication 1 is employed, the server produces the setting information and the keys used in the encrypted communication between the communication source terminal and the communication destination terminal, and then allocates these setting information and keys to the communication source terminal and the communication destination terminal. It should be noted that terminals do not always support the setting information and the keys, which have been allocated. In such a case that both setting information and keys, which are not supported, are allocated to either the communication source terminal or the communication destination terminal, the encrypted communication cannot be carried out between the communication source terminal and the communication destination terminal. 
         [0012]    Also, in order that a communication source terminal and a communication destination terminal confirm validities of the communication counter parties, each of the communication source terminal and the communication destination terminal executes such a process operation for authenticating the communication counter parties. However, in such a case that the communication source terminal performs encrypted communications with a plurality of communication destination terminals, this communication source terminal must authenticate the respective communication destination terminals so as to confirm validities of the communications counter parties, so that processing loads given to this communication source terminal are increased. 
         [0013]    The present invention provides a communication system in which a management server for managing communications between terminals is arranged on a network. 
         [0014]    In the communication system of the present invention, since the below-mentioned steps are carried out, both a communication source terminal and a communication destination terminal commonly own a key which is utilized in an encrypted communication executed between the communication source terminal and the communication destination terminal. 
         [0015]    Both the communication source terminal and the communication destination terminal have previously registered such setting information which may be used in the encrypted communication into the management server. 
         [0016]    When the communication source terminal is connected to the communication destination terminal, the communication source terminal notifies this connection to the management server, and then, the management server searches the plural pieces of the registered setting information for setting information, which of the communication source terminal is coincident with one of the communication destination terminal. 
         [0017]    The management server produces either keys or information which constitutes seeds of the keys based upon the coincident setting information, which are used in the encrypted communication. Then, the management server allocates the produced keys or the produced information to the communication source terminal and the communication destination terminal in combination with the coincident setting information. In such a case that both the setting information and the information which constitutes the seeds of the keys are allocated from the management server to both the communication source terminal and the communication destination terminal, both the communication source terminal and the communication destination terminal produce keys from the information which constitute the seeds of the keys. And then, execute an encrypted communication by employing the setting information allocated from the management server and also either the produced keys or the transmitted keys. 
         [0018]    Also, the above-described communication system is featured by that since the management server authenticates both the communication source terminal and the communication destination terminal by using electronic signatures, therefore this communication system may assume that both the communication source terminal and the communication destination terminal mutually authenticate the communication counter parties. 
         [0019]    In the case that the management server is requested to establish a communication with the communication destination terminal by the communication source terminal, the management server authenticates both of these communication terminals. When the management server can succeed in the authentication, this management server permits the communication between both the terminals. After the management server has permitted this communication, the communication source terminal can be connected to the communication destination terminal. 
         [0020]    Furthermore, the management server may alternatively request such a validation server apparatus (will be referred to as “validation server” hereinafter) for verifying both a public key certificate of the communication source terminal and a public key certificate of the communication destination terminal. 
         [0021]    Since the validation server verifies the public key s, the management server can more firmly authenticate both the communication source terminal and the communication destination terminal. 
         [0022]    In accordance with the present invention, the communication source terminal no longer executes such a process operation that both the setting information and the keys are shared with the communication destination terminal, which are employed so as to perform the encrypted communication between the communication source terminal and the communication destination terminal. 
         [0023]    In addition, both the communication source terminal and the communication destination terminal can firmly carry out the encrypted communication. 
         [0024]    Also, in accordance with the present invention, both the communication source terminal and the communication destination terminal need not directly authenticate the communication counter parties, so that processing loads given to these communication terminals can be reduced. 
         [0025]    These and other benefits are described throughout the present specification. A further understanding of the nature and advantages of the invention may be realized by reference to the remaining portions of the specification and the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a diagram for exemplifying an arrangement of a communication system according to an embodiment mode of the present invention. 
           [0027]      FIG. 2  is a flow chart for exemplifying a process operation in which both a terminal  30  and a management server  10  commonly own a parameter used in an encrypted communication between the terminal  30  and the management server  10 , and exchange a public key. 
           [0028]      FIG. 3  is a flow chart for exemplifying a process operation in which the management server  10  requests a validation server  20  to verify the public key certificate of the terminal  30 , and the validation server  20  responds a validation result. 
           [0029]      FIG. 4  is a flow chart for exemplifying a process operation in which both the terminal  30  and the management server  10  authenticate the counter party with each other by employing electronic signatures, and the terminal  30  and the management server  10  produce keys respectively, which are used in the encrypted communication between the terminal  30  and the management server  10 . 
           [0030]      FIG. 5  is a flow chart for exemplifying a process operation executed until the terminal  30  and the management server  10  perform an encrypted communication after the terminal  30  and the management server  10  have established a connection. 
           [0031]      FIG. 6  is a flow chart for exemplifying a process operation in which both the terminal  30  and the management server  10  accomplish the connection. 
           [0032]      FIG. 7  is a flow chart for exemplifying a process operation in which the terminal  30  registers both an address of the terminal  30  and setting information used in an encrypted communication with another terminal in the management server  10 . 
           [0033]      FIG. 8  is a flow chart for exemplifying a process operation in which when both the terminal  30  and the management server  10  perform a connecting process operation, the management server  10  searches such setting information which have been registered by the terminal  30  and the terminal  40  for coincident setting information. 
           [0034]      FIG. 9  is a flow chart for exemplifying a process operation in which the management server  10  produces keys used in the encrypted communication between the terminal  30  and the terminal  40 , and allocates the produced keys to the terminal  30  and the terminal  40 . 
           [0035]      FIG. 10  is a flow chart for exemplifying a process operation in which the terminal  30  accomplishes the connection with respect to the terminal  40  via the management server  10 . 
           [0036]      FIG. 11  is a diagram for exemplifying a hardware structural example as to each of the management server  10 , the validation server  20 , the terminal  30 , and the terminal  40 . 
           [0037]      FIG. 12  is an example of a content of an address DB  112  held by the management server  10 . 
           [0038]      FIG. 13  is an example of a setting information DB  111  held by the management server  10 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0039]    An embodiment mode of the present invention will now be explained in detail. It should be understood that the present invention is not restricted by this embodiment mode. 
         [0040]      FIG. 1  is a block diagram for indicating an arrangement of a key allocation system according to an embodiment mode of the present invention. 
         [0041]    In the key allocation system of  FIG. 1 , a terminal  30 , another terminal  40 , a management server apparatus (will be referred to as “management server” hereinafter)  10 , a validation server apparatus (will be referred to as “validation server” hereinafter)  20  are connected to a network  50 . 
         [0042]    The terminal  30  and the terminal  40  store thereinto a public key certificate  310  and a public key certificate  410 , respectively, which have been issued from a reliable authentication station respectively. The terminal  30  and the terminal  40  are further provided with setting information registration applying functions  301  and  401 , address registration applying functions  302  and  402 , key/setting information receiving functions  303  and  403 , communicating function with terminal  304  and communicating function with terminal  404 , and also communicating function with management server  305  and communicating function with management server  405 , respectively. The setting information registration applying functions  301  and  401  are employed so as to perform an encrypted communication between these terminals  30  and  40 . The address registration applying functions  302  and  402  are employed so as to register addresses for specifying positions of the relevant terminals on the network  50 . The key/setting information receiving functions  303  and  403  request an execution of an encrypted communication between these terminals  30  and  40 , and receive necessary keys and necessary setting information from the management server  10 . The communicating function with terminal  304  and communicating function with terminal  404  execute an encrypted communication between these terminals  30  and  40 . 
         [0043]    The management server  10  stores thereinto a public key certificate  110 , a setting information DB (database)  111 , and an address DB  112 . The public key certificate  110  has been issued from the reliable authentication station. The setting information DB  111  is employed in order that both the terminal  30  and the terminal  40  execute an encrypted communication. The address DB  112  is used so as to specify positions of both the terminal  30  and the terminal  40  on the network  50 . In this embodiment, an IP (Internet Protocol) address is employed as the above-described terminal address. 
         [0044]    The management server  10  is furthermore equipped with a key producing function  102 , a setting information registering function  103 , a setting information searching function  104 , a key/setting information allocating function  105 , an address registering function  106 , an address searching function  107 , a communicating function with terminal  108 , and a communicating function with validation server  109 . The key producing function  102  produces a key used in an encrypted communication between the terminal  30  and the terminal  40 . The setting information registering function  103  registers setting information by accepting a registering application of setting information issued from either the terminal  30  or the terminal  40 . The setting information searching function  104  searches the setting information which have been registered by the terminal  30  and the terminal  40  for setting information, which of the terminal  30  is coincident with one of the terminal  40  when a connection is established from the terminal  30  to the terminal  40 . The key/setting information allocating function  105  allocates keys and setting information in order to perform an encrypted communication between the terminal  30  and the terminal  40 . The address registering function  106  registers an address to the address DB  112  by accepting a registering application of an address issued from either the terminal  30  or the terminal  40 . The address searching function  107  searches the address DB  112  for an address of a terminal. The communicating function with terminal  108  performs authentication and a communication of a terminal. The communicating function with validation server  109  performs a communication with the validation server  20 . 
         [0045]    The validation server  20  is provided with a certificate validating function  201 , and a communicating function with management server  202 . The certificate validating function  201  confirms a validity of a public key certificate when the management server  10  authenticates the terminal  30 , or the terminal  40 . 
         [0046]    It should be noted that both the respective apparatuses as to the management server  10 , the validation server  20 , the terminal  30 , and the terminal  40 , and the respective functions of these apparatuses may be realized by that a CPU  61  executes predetermined programs which are loaded on the memory  62  in such a computer as shown in, for example,  FIG. 11 . That is, the computer is equipped with the CPU  61 , the memory  62 , an external storage apparatus  63  such as a hard disk drive, a communication apparatus  60 , an input apparatus  65  such as a keyboard and a mouse, an output apparatus  66  such a monitor and a printer, a reading apparatus  67 , and an interface  60  for transmitting/receiving data among these apparatuses. The communication apparatus  64  is communicated to another apparatus via a network, or a LAN (will be referred to as “network” hereinafter) such as the Internet. The reading apparatus  67  reads information from a storage medium  68  having a portability. 
         [0047]    These programs may be previously stored in either the memory  62  or the external storage apparatus  63 , which are employed in the above-described computer. Alternatively, these programs may be conducted via either the detachable storage medium  68  or a communication medium (network, or LAN  50 , or carrier waves and digital signals transmitted via these network and LAN  50 ), if required. 
         [0048]    It should also be understood that in this embodiment, although the terminal can be realized by utilizing the arrangement shown in  FIG. 11 , the present invention is not limited thereto. Each apparatus of the terminal  30  and the terminal  40  shown in  FIG. 1  may be realized by any apparatus equipped with a communication interface capable of being connected to the network  50 . For example, a router, a PC (Personal Computer), a portable telephone, a PDA (Personal Digital Assistant), a television, a refrigerator, and the like may alternatively constitute such a terminal. 
         [0049]    Next, a description is made of operations as to a communication system according to this embodiment mode. 
         [0050]    In the communication system according to this embodiment mode, the terminal  30  establishes a secure communication path with respect to the management server  10  via the network  50 . 
         [0051]    In this case, such an operation is indicated. That is, the terminal  30  establishes an encrypted communication path with respect to the management server  10 , performs an encrypted communication, and then accomplishes the encrypted communication. When the terminal  30  establishes this encrypted communication path, the terminal  30  transmits a public key certificate of the terminal  30  to the management server  10 , whereas the management server  10  requests the validation server  20  to verify a validity of the transmitted public key, and this management server  10  authenticates the terminal  30  based upon a validation result as to the validity of the public key. 
         [0052]    First, both the terminal  30  and the management server  10  exchange a public key certificate  310  and another public key certificate  110  in accordance with a flow operation shown in  FIG. 2 . 
         [0053]    The communicating function with management server  305  transmits one, or more candidates for parameters which are used to execute an encrypted communication with respect to the management server  10  (step  1000 ). The parameters used in the encrypted communication contain a sort of an encryption algorithm used in encryption of communication data, a length of a key, a sort of hash function which is employed so as to detect an alteration of the communication data, and the like. 
         [0054]    The communicating function with terminal  108  receives the candidate of the encrypted communication parameter transmitted from the terminal  30  (step  1002 ). 
         [0055]    The management server  10  selects one of the parameters which can be used by the management server  10  from the received candidates for the parameters, and then transmits the selected parameter to the terminal  30  by the communicating function with terminal  108  (step  1004 ). 
         [0056]    The communicating function with management server  305  receives the parameter selected by the management server  10  (step  1006 ). 
         [0057]    Since the process operations defined from the step  1000  to the step  1006  are executed, both the terminal  30  and the management server  10  commonly own the parameter. 
         [0058]    The communicating function with management server  305  transmits a request for the public key certificate  110  of the management server  10  to the management server  10  (step  1008 ). 
         [0059]    The communicating function with terminal  108  receives the request for the public key certificate  110  sent from the terminal  30  (step  1010 ). 
         [0060]    In the case that the management sever  10  holds the public key certificate  110  received by the request in the step  1010  (YES in step  1012 ), the management server  10  transmits both the public key certificate  110  of the management server  10  and the request for the public key certificate of the terminal  30  to the terminal  30  by the communicating function with terminal  108  (step  1014 ). 
         [0061]    The communicating function with management server  305  receives both the public key certificate  110  of the management server  10  and the request for the public key certificate of the terminal  30  (step  1016 ). 
         [0062]    In such a case that the terminal  30  holds the public key certificate  310  whose request has been received in the step  1016  (YES in step  1018 ), the terminal  30  transmits the public key certificate  310  of the terminal  30  by the communicating function with management server  305  to the management server  10  (step  1020 ). 
         [0063]    The communicating function with terminal  108  receives the public key certificate  310  of the terminal  30  from the terminal  30  (step  1022 ). 
         [0064]    The communicating function with terminal  108  transmits a reception notification as to the public key certificate  310  of the terminal  30  (step  1024 ). 
         [0065]    The communicating function with management server  305  receives the reception notification as to the public key certificate  310  of the terminal  30  from the management server  10  (step  1026 ). 
         [0066]    The communicating function with management server  304  verifies the public key certificate  110  by verifying a valid time limit and a signature of the public key certificate  110  received in the step  1016  (step  1028 ). 
         [0067]    In the case that the terminal  30  can succeed in the validation of the public key certificate  110  (YES in step  1030 ), the process operation is advanced to a process operation of  FIG. 3 . 
         [0068]    In the case that the judgement result becomes NO in the above-explained step  1012 , step  1018 , or step  1030 , the process operation is advanced to a step  1316 (A) in which a process operation for accomplishing a communication between the terminal  30  and the management server  10  is carried out. It should be noted that  FIG. 6  shows such a case that the terminal  30  issues the request for accomplishing the communication. In the case that the process operation is advanced from the step  1012 , since the management server  10  issues the request for accomplishing the communication, the operation of the terminal  30  is replaced by the operation of the management server  10 . 
         [0069]    Next, the management server  10  requests the validation server  20  to verify the public key certificate of the terminal  30 , and then accepts a validation result in accordance with a flow chart shown in  FIG. 3 . 
         [0070]    The communicating function with validation server  109  transmits the public key certificate  310  of the terminal  30  to the validation server  20  (step  1100 ). 
         [0071]    The communicating function with management server  202  receives the public key certificate  310  (step  1102 ). 
         [0072]    The validation server  20  verifies the received public key certificate  310  by the certificate validating function  201 . It should also be understood that when validation of the public key certificate  201  is carried out, the validation server  20  verifies a valid time limit, a signature, and an invalidated status of the public key certificate (step  1104 ). 
         [0073]    In the case that validation  1104  of the public key certificate  310  cannot succeed (NO in step  1106 ), the validation server  20  transmits a validation failure notification to which a signature of the validation server  20  has been applied, to the management server  10  by the communicating function with management server  202  (step  1108 ). 
         [0074]    In the case that validation  1104  of the public key certificate  310  can succeed (YES in step  1106 ), the validation server  20  transmits a validation success notification to which a signature of the validation server  20  has been applied, to the management server  10  by the communicating function with management server  202  (step  1110 ). 
         [0075]    The management server  10  receives either the validation failure notification or the validation success notification, which have been transmitted in either the step  1108  or the step  1110  by the communicating function with validation server  109 , and verifies the signature of the validation server  20  which has been applied to the notification so as to confirm that the notification has been surely transmitted form the validation server  20  and has not been altered (step  1112 ). 
         [0076]    When the management server  10  receives the validation success notification in the step  1112 , the management server  10  advances the process operation to a process operation (D) of  FIG. 4 . When the management server  10  receives the validation failure notification in the step  1112 , the management server  10  advances the process operation to a step  1316 (A) of  FIG. 6  in order to accomplish the connection to the terminal  30 . It should also be noted that since the management server  10  issues the communication accomplish request, the operation of the terminal  30  is replaced by the operation of the management server  10  of  FIG. 6 . 
         [0077]    Next, as indicated in  FIG. 4 , both the terminal  30  and the management server  10  may authenticate the counter party with each other in such a manner that the electronic signatures are attached to the commonly-owned information in the step of  FIG. 2 , the resulting commonly-owned information is exchanged, and then, the exchanged electronic signatures are verified. Thereafter, the terminal  30  and the management server  10  commonly own the keys. It should also be understood that as the commonly-owned information, arbitrary information within the information exchanged in the step of  FIG. 2  may be utilized. 
         [0078]    Firstly, the terminal  30  produces an electronic signature with respect to the commonly-owned information, and attaches the electronic signature to the commonly-owned information, and then, transmits the resulting commonly-owned information to the management server  10  by the communicating function with management server  305  (step  1200 ). 
         [0079]    The communicating function with terminal  305  receives both the commonly-owned information and the electronic signature from the terminal  30  (step  1202 ). 
         [0080]    The management server  10  verifies the received electronic signature by employing the public key of the public key certificate  310  of the terminal  30  received in the step  1022  (step  1204 ). 
         [0081]    In such a case that the management server  10  can succeed the validation of the electronic signature (YES in step  1206 ), the management server  10  produces an electronic signature with respect to the commonly-owned information, and attaches the electronic signature to the commonly-owned information, and then, transmits the resulting commonly-owned information to the terminal  30  by the communicating function with terminal  108  (step  1208 ). 
         [0082]    The communicating function with management server  305  receives both the commonly-owned information and the electronic signature from the management server  10  (step  1210 ). 
         [0083]    The terminal  30  verifies the received electronic signature by employing the public key of the public key certificate  110  of the management server  10  received in the step  1016  (step  1212 ). 
         [0084]    In the case that the terminal  30  can succeed the validation of the electronic signature (YES in step  1214 ), the process operation is advanced to a key producing step  1216  which is provided for an encrypted communication between the terminal  30  and the management server  10 . 
         [0085]    The terminal  30  produces such a key which is used to perform an encrypted communication with respect to the management server  10  based upon the parameters which have been commonly owned from the step  1000  to the step  1006  (step  1216 ). 
         [0086]    The management server  10  also produces such a key which is used to perform an encrypted communication with respect to the terminal  30  based upon the parameters which have been commonly owned from the step  1000  to the step  1006  (step  1218 ). 
         [0087]    In the case that the judgment result becomes NO in either the step  1206  or the step  1214  (in the case that validation of electronic signature fails), the process operation is advanced to a step  1316 (A) of  FIG. 6 . It should also be noted that the process operation of  FIG. 6  indicates such a case that the terminal  30  requests a completion of the communication operation. When the process operation is advanced from the step  1206 , since the management server  10  issues a communication completion request, the operation of the terminal  30  is replaced by the operation of the management server  10 . 
         [0088]    Since the above-described process operations are executed, the terminal  30  authenticates the management server  10 , and the management server  10  authenticates the terminal  30 . Also, both the terminal  30  and the management server  10  commonly own the key which is employed so as to perform the encrypted communication between the terminal  30  the management server  10 . 
         [0089]    If the terminal  30  and the management server  10  could authenticate the counter parties with each other, then both the terminal  30  and the management server  10  establish a communication connection so as to execute an encrypted communication. 
         [0090]      FIG. 5  is a sequence diagram for describing such a step that a connection is established so as to execute the above-explained encrypted communication and then, this encrypted communication is carried out. 
         [0091]    The communicating function with management server  305  transmits a data transfer permission request to the management server  10  (step  1300 ), and the communicating function with terminal  108  receives this transmitted data transfer permission request (step  1302 ). 
         [0092]    The communicating function with terminal  108  transmits both the data transfer permission and a data transfer permission with respect to the terminal  30  to the terminal  30  (step  1304 ), and then, the communicating function with management server  305  receives this data transfer permission and the data transfer permission request (step  1306 ). 
         [0093]    The communicating function with management server  305  transmits the data transfer permission to the management server  10  (step  1308 ), and the communicating function with terminal  108  receives this data transfer permission (step  1310 ). 
         [0094]    Since the above-described process operations are carried out, both the terminal  30  and the management server  10  mutually issue the data transfer permissions, so that the connection may be established (step  1312 ). 
         [0095]    After the connection has been established, both the terminal  30  and the management server  10  execute an encrypted communication by employing both the parameters used for the encrypted communication which have been commonly used in the step  1000  through step  1006  of  FIG. 2 , and the keys used for the encrypted communication which have been produced in the step  1216  and the step  1218  (step  1314 ). 
         [0096]    When the terminal  30  and the management server  10  need not require the encryption path, both the terminal and the management server  10  accomplish the connection in accordance with the sequential operation shown in  FIG. 6 . In the case that the above-described encrypted communication is accomplished, firstly, the communicating function with management server  305  transmits a communication completion request with respect to the management server  10  to the management server  10  (step  1316 ). 
         [0097]    The communicating function with terminal  108  receives this communication completion request (step  1318 ). 
         [0098]    The communicating function with terminal  108  transmits both a communication completion permission and a communication completion permission request to the terminal  30  (step  1320 ), and then, the communicating function with management server  305  receives these communication accomplish permission and communication permission request (step  1322 ). 
         [0099]    The communicating function with management server  305  transmits the communication completion permission to the management server  10  (step  1324 ), and the communicating function with terminal  108  receives this communication completion permission (step  1326 ). 
         [0100]    Since the above-described process operation is carried out, both the terminal  30  and the management server  10  have mutually issued the communication completion permissions, so that the connection is completed (step  1328 ). 
         [0101]    As previously explained, since the process operations defined from  FIG. 2  to  FIG. 6  are carried out, both the terminal  30  and the management server  10  can mutually authenticate the counter parties with each other, and can establish the encrypted communication path between the terminal  30  and the management server  10  so as to execute the encrypted communication, and then, can complete the encrypted communication. 
         [0102]    In this embodiment mode, in order that the management server  10  strictly authenticates the terminal  30 , the management server  10  requests the validation server  20  to verify the public key certificate  310  by executing the process operation shown in  FIG. 3 . 
         [0103]    Furthermore, in order that the terminal  30  strictly authenticates the management server  10 , the terminal  30  may alternatively request the validation server  20  to verify the publication key certificate  110 . Instead of the process operations defined in both the step  1028  and the step  1030 , since the process operations executed by the terminal  30  are replaced by these by the management server  10  in  FIG. 3 , the terminal  30  may alternatively request the validation server  20  to verify the public key certificate  110 . 
         [0104]    In a flow chart shown in  FIG. 7 , while the terminal  30  employs the encrypted communication path established by the operation sequences explained from  FIG. 2  to  FIG. 5 , the terminal  30  registers both an address and setting information used to execute an encrypted communication with another terminal into the management server  10 . 
         [0105]    First of all, both the terminal  30  and the management server  10  establish the above-explained encrypted communication path by executing the process operations defined from the step  1000  to the step  1030 , from the step  1100  to the step  1114 , from the step  1200  to the step  1218 , and also, from the step  1300  to the step  1312  (these steps are combined with each other which will be referred to as “step  2000 ”). 
         [0106]    Next, both the address registration applying function  302  and the setting information registration applying function  301  of the terminal  30  request the management server  10  to register the address of the terminal  30 , and also to register the setting information used to perform the encrypted communication with another terminal by employing the communicating function with management server  305  (step  2002 ). It should also be noted that in this step  2002 , more than one registration request for the setting information is transmitted. It should also be understood that the setting information contains, for example, a sort of encryption algorithm used so as to encrypt communication data, a length of a key, a sort of hash function employed so as to detect alternation of communication data, and the like. 
         [0107]    The communicating function with terminal  108  receives the relevant address and the setting information used for the encrypted communication (step  2004 ). 
         [0108]    The address registering function  106  of the management server  10  registers this received address into the address DB  112  by the address registering function  106  of  FIG. 1  (step  2006 ), the detailed explanation of which will be made later. 
         [0109]    The setting information registering function  103  registers this received setting information into the setting information DB  111  (step  2008 ). 
         [0110]    In order that the management server  10  notifies such a fact that the above-described address and setting information have been registered to the terminal  30 , the management server  10  transmits a registration completion notification to the terminal  30  by employing the communicating function with terminal  108  (step  2010 ). The communicating function with management server  305  receives this registration completion notification (step  2012 ). 
         [0111]    Both the terminal  30  and the management server  10  execute the process operations defined from the above-described step  1316  to step  1326  so as to complete the connection (these steps are combined with each other which will be referred to as “step  2014 ”). 
         [0112]    Since the above-described process operations of  FIG. 7  are carried out, the terminal  30  can register the own address and the setting information which is used so as to perform the encrypted communication with another terminal into the management server  10 . 
         [0113]    Since process operations similar to those of  FIG. 7  are carried out, the terminal  40  can also register the address of the own terminal  40  and the setting information which is used so as to perform the encrypted communication with another terminal into the management server  10  by way of both the address registration applying function  402  and the setting information registration applying function  401 . 
         [0114]    In the case that the terminal  40  performs the registering operation, both the terminal and the management server  10  execute such a flow operation that the terminal  30  of  FIG. 7  has been substituted by the terminal  40 . 
         [0115]    It should also be noted that both the terminal  30  and the terminal  40  may alternatively delete the addresses and the setting information, which have been registered in the management server  10 . When these addresses and setting information are deleted, the terminal  30  and the terminal  40  execute such a process operation that “registration” of  FIG. 7  has been replaced by “deletion.” 
         [0116]    In the process operation of  FIG. 7 , both the terminal  30  and the terminal  40  register addresses into the management server  10 , which are allocated to the own terminals. In the case that the addresses allocated to the own terminals are changed, the terminal  30  and the terminal  40  are required to again perform the process operations of  FIG. 7  in order to register the latest addresses. 
         [0117]    For instance, in the case that an address corresponds to an IP address and a terminal has dynamically accepted an IP address allocation, when a power supply of the terminal is turned OFF, ON, and the terminal is reset, there are some possibilities that the IP address is changed. Also, in such a case that a terminal accomplishes a connection to the network and is connected to another network at a move destination, there are some possibilities that an IP address of the terminal is changed. When there are some possibilities that the IP address of the terminal has been changed, since the terminal again performs the process operation of  FIG. 7 , the terminal registers the latest IP address to a management server. 
         [0118]    If both the terminal  30  and the terminal  40  register both positions (IP addresses) on the network and the setting information for the encrypted communication between the other terminal into the management server  10  in the sequential operation of  FIG. 7 , then the terminal  30  executes a connection process operation with respect to the terminal  40  via the management server  10  in accordance with the flow charts shown in  FIG. 8  and  FIG. 9 . 
         [0119]    Both the terminal  30  and the terminal  40  establish an encrypted communication path by executing the process operations defined from the above-described step  1000  to step  1030 , the process operations defined from the step  1100  to step  1114 , the process operations defined from the above-described step  1200  to step  1218 , the process operations defined from the step  1300  to step  1312  (these steps are combined with each other, which will be referred to as “step  2100 ”). 
         [0120]    The key/setting information receiving function  303  of the terminal  30  transmits a connection request for the terminal  40  to the management server  10  by the communicating function with management server  305  (step  2102 ), and then, the communicating function with terminal  108  receives this connection request (step  2104 ). It should also be understood that the connection request contains such an information, as an ID for identifying a connection counter party (terminal  40 ) will be referred to as “terminal ID” hereinafter. As the terminal ID, a fixed item within a domain may be used. For instance, a name of a terminal, and a MAC address of a terminal may be used. Also, in such a closed domain as an internal form, such information may also be used, namely, a mail address of a user of a terminal, SIP-URI of a terminal, and FQDN (Fully Qualified Domain Name) of a terminal may be used. 
         [0121]    In order to acquire an address of the terminal  40  corresponding to a connection destination of the terminal  30 , the management server  10  searches the address DB  112  of  FIG. 2  based upon the address searching function  107  of  FIG. 1 , while a terminal ID is used as a key (step  2106 ). 
         [0122]    The management server  10  searches the setting information DB  111  of  FIG. 1  so as to acquire candidates of the setting information as to the terminal  30  and the terminal  40 . Then, the management sever  10  searches the acquired setting information by the setting information searching function  104  of  FIG. 1 , for such setting information, which of the terminal  30  is coincident with one of terminal  40  each other from (step  2108 ). 
         [0123]    When one, or more pieces of setting information of the terminal  30  and setting information of the terminal  40  are made coincident with each other (YES in step  2110 ), the management server  10  establishes an encrypted communication path between the terminal  40  and the own management server  10  by executing the process operations defined from the step  1000  to the step  1030 , the process operations defined from the step  1100  to the step  1114 , the process operations defined from the step  1200  to the step  1218 , and the process operations defined from the step  1300  to the step  1312  (these steps are combined with each other, which will be referred to as “step  2112 ”). 
         [0124]    In order that the encrypted communication path is established between the management server  10  and the terminal  40 , it is so assumed that such process operations of  FIG. 2 ,  FIG. 4 , and  FIG. 5  that the terminal  30  has been replaced by the management server  10  and the management server  10  has been replaced by the terminal  40  are carried out, while both the management server  10  and the terminal  40  are equipped with the above-explained functions which are required to execute these process operations. 
         [0125]    Furthermore, in the step  2112 , in order that the management server  10  requests the validation server  20  to verify a public key certificate of the terminal  40 , the operation of the management server  10  is advanced from the step  1026  of  FIG. 2  to “C” of  FIG. 3 , and advanced from “D” of  FIG. 3  to “B” in  FIG. 4 . Also, the operation of the terminal  40  is advanced from “C” of  FIG. 2  to “D” of  FIG. 4 . 
         [0126]    In the case that the setting information of the terminal  30  is not made coincident with the setting information of the terminal  40  in the step  2110 , the process operation is advanced to “A” of  FIG. 6 , and the management server  10  describes such an indication that the connection is not permitted because the setting information of the terminal  30  is not made coincident with the terminal  40  in a message under processing operation of  FIG. 6 , and then, notifies the resulting message to the terminal  30  so as to complete the connection between the terminal  30  and the management server  10 . It should also be noted that  FIG. 6  shows the process operations in the case that the terminal  30  requests the completion of the communicating operation. In such a case that the process operation is advanced from the step  2110 , since the management server  10  issues the communication completion request, the operations of the terminal  30  are replaced by the operations of the management server  10 . 
         [0127]    Subsequent to the step  2112 , the communicating function with terminal  108  transmits to the terminal  40  by using the established encrypted communication path, the connection request which has been issued from the terminal  30  to the terminal  40  and has been received in the step  2104  (step  2114 ). The communicating function with management server  405  receives this transmitted connection request (step  2116 ). 
         [0128]    The terminal  40  judges as to whether the received connection request is permitted, or refused based upon either the status of the own terminal or the status of the user (for instance, whether or not communication can be presently carried out), and a filtering function by the specific policy of the terminal  40  (step  2118 ). 
         [0129]    The communicating function with management server  405  transmits the above-explained judgment result to the management server  10  (step  2120 ), and then, the communicating function with terminal  108  receives this judgement result (step  2122 ). 
         [0130]    The communicating function with terminal  108  transfers the received judgement result to the terminal  30  (step  2124 ), and then, the communicating function with management server  305  receives this transmitted judgement result (step  2126 ). 
         [0131]    Since the above-described process operations are carried out, an agreement can be made as to whether or not the connection between the terminal  30  and the terminal  40  is permitted by employing the encrypted communication path established between the terminal  30  and the management server  10 , and also, the encrypted communication path established between the terminal  40  and the management server  10 . 
         [0132]    Next, in accordance with a flow chart shown in  FIG. 9 , the management server  10  produces a key used in an encrypted communication between the terminal  30  and the terminal  40  based upon the coincident setting information which has been searched for in the step  2108  of  FIG. 8 , and then, allocates the key used in the encrypted communication and the setting information to both the terminal  30  and the terminal  40 . Both the terminal  30  and the terminal  40  establish an encrypted communication path by employing the allocated keys and setting information. 
         [0133]    The terminal  30 , the management server  10 , and the terminal  40  judge a result as to whether or not the connection has been permitted in the step  2118  (step  2128 , step  2130 , step  2132 ). Since the judgement result of the step  2118  is reflected to the judging operations of the step  2128 , the step  2130 , and the step  2132 , all of the judgment results become the same results, namely either “YES” or “NO.” 
         [0134]    In the case that the judgment results become “NO”, the terminal  30 , the management server  10 , and the terminal  40  accomplish the process operations. 
         [0135]    In the case that the judgment results become YES, the key producing function  102  of the management server  10  produces a key used in an encrypted communication between the terminal  30  and the terminal  40  based upon the coincident setting information has been searched for in the step  2108  (step  2134 ). It should also be noted that in the step  2134 , instead of this key used in the encrypted communication, information which constitutes a seed of the key used in the encrypted communication may be the alternatively produced. 
         [0136]    The management server  10  transmits both either the key or the information which constitutes the seed of the key, which have been produced in the step  2134 , and also the coincident setting information which has been searched for in the step  2108  by the key/setting information allocating function  105  to both the terminal  30  and the terminal  40  (step  2138 ). The terminal  30  and the terminal  40  receive the above-described information by the key/setting information receiving functions  303  and  403  (step  2136  and step  2140 ). 
         [0137]    Both the communicating function with terminal  304  of the terminal  30  and the communicating function with terminal  404  of the terminal  40  establish an encrypted communication path by utilizing the keys and the setting information used for the encrypted communication between the terminal  30  and the terminal  40  (step  2142 ). 
         [0138]    In such a case that the management server  10  produces the information which constitutes the seed of the key used for the encrypted communication between the terminal  30  and the terminal  40  in the step  2134 , and allocates the produced information in the step  2138 , both the key/setting information receiving functions  304  and  403  produce keys used for this encrypted communication by employing the information which constitute the seeds of the keys used for the encrypted communication and has been allocated. Then, both the communicating function with terminal  304  and communicating function with terminal  404  establish encrypted communication paths by utilizing the produced keys and the received setting information. 
         [0139]    Both the terminal  30  and the terminal  40  perform an encrypted communication by employing the above-explained encrypted communication paths which have been established by the communicating function with terminal  304  and communicating function with terminal  404  (step  2144 ). 
         [0140]    Since the above-explained process operations are carried out, the management server  10  allocates both either the keys or the information which constitutes the seeds of the keys and the setting information to both the terminal  30  and the terminal  40 , which are required for the encrypted communications between the terminal  30  and the terminal  40 , so that both the terminal  30  and the terminal  40  carry out the encrypted communication. 
         [0141]    When the terminal  30  and the terminal  40  complete the encrypted communication (step  2144 ), the terminal  30  and the terminal  40  accomplish the communicating operation in accordance with a flow chart of  FIG. 10 . 
         [0142]    The communicating function with management server  305  transmits a completion request to the management server  10  (step  2146 ), and then, the communicating function with terminal  108  receives this completion request (step  2148 ). 
         [0143]    The communicating function with terminal  108  transfers the received completion request to the terminal  40  (step  2150 ), and then, the communicating function with management server  405  receives this completion request (step  2152 ). 
         [0144]    The communicating function with management server  405  transmits completion permission to the management server  10  (step  2154 ), and then, the communicating function with terminal  108  receives this completion permission (step  2156 ). 
         [0145]    The communicating function with terminal  108  transfers the received completion permission to the terminal  30  (step  2158 ), and then, the communicating function with management server  405  receives this completion permission (step  2160 ). 
         [0146]    Since the above-described process operations of  FIG. 10  are carried out, both the terminal  30  and the management server  10  complete the connection of the encrypted communication path between the terminal  30  and the management server  10 , which has been established in the step  2100  of  FIG. 8  (step  2162 ), whereas both the terminal  40  and the management server  10  complete the connection of the encrypted communication path between the terminal  40  and the management server  10 , which has been established in the step  2112  of  FIG. 8  (step  2164 ). 
         [0147]    Also, both the terminal  30  and the terminal  40  complete the connection of the encrypted communication path between the terminal  30  and the terminal  40 , which has been established in the step  2142  of  FIG. 9  (step  2166 ). 
         [0148]    It should also be understood that both the terminal  30  and the terminal  40  need not always execute the flow operations shown in  FIG. 10  so as to accomplish the communicating operation, but may alternatively accomplish the communicating operation without executing the flow operation of  FIG. 10 . 
         [0149]    In the case that the flow operation indicated in  FIG. 10  is not carried out, since the terminal  30 , the management server  10 , and the terminal  40  need not perform the process operations of  FIG. 10 , a process load is lowered. Also, if the encrypted communication paths established in the step  2100  and the step  2112  are accomplished before the step  2142 , then the communication resource between the terminal  30  and the management server  10 , and the communication resource between the management server  10  and the terminal  40  may be reduced. 
         [0150]    Also, both the terminal  30  and the management server  10  accomplish the encrypted communication path which has been established in the step  2100  after the step  2136  and the step  2138 , and may again establish an encrypted communication path after the step  2144 . Alternatively, both the terminal  40  and the management server  10  accomplish the encrypted communication path which has been established in the step  2112  after the step  2138  and the step  2140 , and may again establish an encrypted communication path after the step  2144 . 
         [0151]    In this alternative case, during the encrypted communication of the step  2144 , either both the terminal  30  and the management server  10  or both the management server  18  and the terminal  40  need not establish the encrypted communication path, so that the communication resource may be reduced. 
         [0152]    In the above-described process operation of  FIG. 8 , when the encrypted communication path is established in the step  2100 , both the terminal  30  and the management server  10  authenticate the counter parties with each other, and also, when the encrypted communication path is established in the step  2112 , both the terminal  40  and the management server  10  authenticate the counter parties with each other. As a result, the terminal  30  can confirm a validity of the terminal  40  via the management server  10 , and the terminal  40  can confirm a validity of the terminal  30  via the management server  10 . 
         [0153]    Also, since the above-described process operations of  FIG. 8  and  FIG. 9  are carried out, the management server  10  searches the plural setting information for the encryption communicating operations between the terminal  30  and the terminal  40  for the coincident setting information, the plural setting information have been previously registered by the terminal  30  and the terminal  40 , and the management server  10  delivers both the coincident setting information and either the keys for the encryption communicating operations or the information which constitutes the seeds of the keys. As a result, both the terminal  30  and the terminal  40  can perform the encryption communicating operation by employing the allocated keys and the allocated setting information. 
         [0154]    In this embodiment mode, in such a case that a function capable of handling personal information of the users as to the terminals  30  and  40  is additionally provided with the management server  10 , in order to avoid that the personal information of the users transmitted by the terminals  30  and  40  to the management sever  10  is leaked, in the step  2000  of  FIG. 7 , concretely speaking, since the process operations defined from  FIG. 2  to  FIG. 6  are carried out, the encrypted communication path is established. In such a case that the management server  10  does not handle the personal information, the communication path need not be encrypted. In the case that the communication path is not encrypted, in the steps for establishing the encrypted communication paths of  FIG. 2 ,  FIG. 3 ,  FIG. 4 ,  FIG. 5 , and  FIG. 6 , the above-explained step  1216  and step  1218  of  FIG. 4  are omitted, whereas in the above-described step  1314  of  FIG. 5 , the communicating operation is not encrypted. 
         [0155]    Next, a partial operation of the flow operations which have been so far described will now be explained in detailed. 
         [0156]    In the step  2006  of  FIG. 7 , the address of the terminal  30  is registered in the address DB  112  of  FIG. 1 . A table  700  shown in  FIG. 12  exemplifies an example of the address DB (database)  112 . 
         [0157]    Subsequently, registering and searching operations of the address DB  112  will be explained. 
         [0158]    The address registration applying function  302  of the terminal  30  transmits the address to the management server  10  in the registration request transmission in the step  2002  of  FIG. 2 . 
         [0159]    The address registering function  106  of the management server  10  registers the address of the terminal  30  received in the step  2004  in the address DB  112  in the step  2006 . 
         [0160]    The address DB  112  may be constituted in the form of, for example, the table  700  shown in  FIG. 12 . The table  700  stores thereinto pairs of information (terminal IDs) for specifying terminals and addresses, which are contained in the connection request which is received by the management server  10  in the step  2104 . 
         [0161]    In the example of the table  700 , respective terminal IDs and respective addresses of the terminal  30  and the terminal  40  are stored in an entry  702  and another entry  704 . It should also be noted that as to a single terminal, a single entry is stored. In such a case that the information indicated in the example of the table  700  has already been registered in the address DB  112 , when a terminal again registers an IP address, the address registering function  106  updates a portion of an IP address of such an entry related to this terminal by the process operation of the step  2006 . 
         [0162]    Also, the address searching function  106  of the management server  10  searches the address of the terminal  40  corresponding to the connection request destination of the terminal  30  in the step  2106  of  FIG. 8 . 
         [0163]    In the step  2106 , the address searching function  107  of the management server  10  acquires the IP address information of the terminal  40  with reference to the entry  704  of  FIG. 12 . 
         [0164]    In the step  2008  of  FIG. 7 , both the terminal  30  and the terminal  40  register one, or more pieces of the setting information for the encrypted communication, which can be used in the encrypted communications with respect to other terminals into the setting information DB  111  of  FIG. 1 . In the step  2108  of  FIG. 8 , the terminal  30  and the terminal  40  search for the coincident setting information from the plural setting information with reference to the setting information DB  111 . 
         [0165]    Subsequently, both the registering operation of the setting information DB  111  and the searching operation as to the coincident setting information with respect to this setting information DB  111  will be described. 
         [0166]    The setting information registration applying function  301  of one terminal transmits one, or more candidates as to the setting information for the encrypted communication with respect to another terminal to the management server  10  by transmitting the setting information registration request in the step  2002 . It should also be noted that when two, or more pieces of the setting information are registered, priority orders are applied to candidates of the setting information, and then, the resulting candidates are transmitted. 
         [0167]    The setting information registering function  103  of the management server  10  registers the candidate as to the setting information for the encrypted communication of the terminal, which has been received in the step  2004 , into the setting information DB  111  in the step  2008 . 
         [0168]    The setting information DB  111  may be constituted by tables every terminal, for example, a table  800  as to the setting information of the terminal  30  and another table  810  as to the setting information of the terminal  40  as represented in  FIG. 13 . 
         [0169]    In the example of the table  800 , pairs made between candidates for the setting information of the terminal  30  and priority orders are held in an entry  802 , an entry  804 , and an entry  806 . 
         [0170]    In such a case that the information indicated in the table  800  has already been registered in the setting information DB  111 , when a terminal again registers a candidate for setting information, the setting information registering function  103  of the management server  10  updates such a table related to the relevant terminal in accordance with the step  2008 . 
         [0171]    Also, the setting information searching function  104  of the management server  10  searches the plural setting information for the encrypted communications of the terminal  30  and the terminal  40  for coincident setting information in the step  2108  of  FIG. 8 . 
         [0172]    In the step  2108 , the setting information searching function  104  of the management server  10  searches the setting information for the encrypted communications for the coincident setting information with reference to both the table  800  and the table  810  of  FIG. 13 . 
         [0173]    First of all, such entries that contents of setting information thereof are made coincident with each other are extracted from the entries of the table  800  and the table  810 . In the example of  FIG. 13 , both the entry  802  and the entry  814  are extracted, and both the entry  804  and the entry  812  are extracted. 
         [0174]    It should also be understood that when there is no such entries that contents of setting information thereof are coincident with each other, the setting information searching function  104  fails in the searching operation. 
         [0175]    The information (setting values) transmitted in the step  2002  has been described in the entries of the respective setting information as to the table  800  and the table  810 . In the step  2108 , such entries that all of the setting values described in these entries are made coincident with each other are extracted. For instance, in the case that a sort of encryption algorithm employed so as to encrypt communication data, a length of a key, a sort of hash function used so as to detect an alteration of the communication data are described in one entry, such an entry that all of these three setting values are made coincident with each other is extracted in the step  2108 . 
         [0176]    Setting values which are described in an entry may be described in such a manner that the setting values are adjustable, for example, an encryption algorithm: algorithm “A”, a length of a key: longer than, or equal to 64 bits, and a hash function: either function “A” or function “B”. In this case, when this setting information is compared with another setting information, namely, an encryption algorithm: algorithm “A”, a length of a key: longer than, or equal to 128 bits, and a hash function: either function “B” or function C in the step  2108 , the first-mentioned setting information is not completely coincident with the last-mentioned setting information. However, since the respective settable ranges are overlapped with each other, for example, the encryption algorithm: algorithm “A”, the length of the key: 128 bits, and the hash function: function “B” may be recognized as the coincident entry. 
         [0177]    In the case that settable ranges of plural items are overlapped with each other, setting values may be alternatively determined in accordance with predetermined priority degrees among the setting items. 
         [0178]    In the case that there are plural entries whose setting information are coincident with each other, one set of setting information is selected in accordance with predetermined priority orders of terminals in such a manner that, for instance, a terminal which accepts a connection request owns a top priority, as compared with another terminal which issues the connection request. 
         [0179]    In the example of  FIG. 13 , in such a case that it is previously determined that the terminal  40  which accepts the connection request owns the top priority, as compared with the terminal  30  which issues the connection request, the management server  10  refers to the priority order column (priority order of entry  812  is 1, and priority order of entry  814  is 2) of the terminal  40  contained in the coincident entries, and selects the set “B” having the higher priority order, and thus, can succeed in the searching operation of the setting information in the step  2108 . 
         [0180]    Also, the management server  10  may alternatively select one set of setting information from the coincident entries in accordance with a predetermined selection base. 
         [0181]    In this case, the setting information DB (table  800  and table  810 ) need not provide a priority order column. A terminal registers one, or more pieces of the setting information into the setting information DB  111 , whereas the management sever  10  searches the setting information for plural pieces of such setting information which are coincident with each other, and then, selects one set of setting information from the plural pieces of the coincident setting information in accordance with the predetermined selection base. 
         [0182]    As to the selection base, for instance, an encryption strength of an encryption algorithm may be employed as this selection base, or a length of a key used so as to encrypt communication data may be employed as a selection base in a communicating operation which requires a higher security. Alternatively, in the case that communication performance is required, ease of encrypting process operation by an encryption algorithm, and/or ease of calculating process operation by a hash function which is employed so as to detect an alteration may be employed as the selection base. 
         [0183]    Although this embodiment mode has exemplified the communicating operation for designating the terminal ID, a user who uses a terminal may be alternatively designated as a communication counter party. 
         [0184]    In such a case that a user who uses a terminal is designated, while both a public key certificate owned by the user and a user ID have been previously stored in the storage medium  68  having the portability, the storage medium  68  is inserted into the reading apparatus  67  of the terminal, so that an attribute of the user may be alternatively reflected to the terminal. 
         [0185]    In such a case that the user extracts the storage medium  68  having the portability from the reading apparatus  67 , the attribute of the user is not reflected to the terminal. 
         [0186]    If such a process operation is carried out, then it is possible to judge as to whether or not the user is operating the terminal when a connection is made from another terminal. That is, at the same time when the attribute of the user is reflected to the terminal, the process operation of  FIG. 7  is carried out so as to register both the user ID and the address of the terminal in the management server  10 , and at the same time when the attribute of the user is not reflected to the terminal, such a process operation that “register” is replaced by “delete” in the flow chart of  FIG. 7  is carried out. As a result, in the case that terminals are under use, the user can be connected without paying a specific attention to such a fact that user utilizes which terminal. 
         [0187]    The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereto without departing from the spirit and scope of the invention as set forth in the claims. 
         [0188]    It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.