Abstract:
Provided is a communication terminal capable of suppressing the phenomenon of personal information being transmitted contrary to the will of the person. A communication terminal ( 1 ) comprises communication sections ( 20, 200 ), a first storage section ( 131 ) for storing first information relating to a first communication terminal, an information creating section ( 121 ) for creating information which is transmitted to a second communication terminal different from the first communication terminal by the communication section ( 20 ), a reply requesting section ( 122 ) which allows the communication section ( 200 ) to transmit information for requesting a reply of whether or not the transmission of the created information is permitted to the first communication terminal when the information created by the information creating section ( 121 ) includes part or all of the first information, and a first communication permitting section ( 123 ) which allows the communication section ( 20 ) to transmit the created information to the second communication terminal when the communication section ( 200 ) has received a permission reply to permit the transmission of the created information from the first communication terminal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of International Application No. PCT/JP2010/055449, filed Mar. 26, 2010, which claims the benefit of Japanese Application No. 2009-077340, filed Mar. 26, 2009, and Japanese Application No. 2009-077795, filed Mar. 26, 2009, the entire contents of all of which are incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The present invention relates to a communication terminal such as a cellular telephone device. In addition, the present invention relates to a communication system including a plurality of communication terminals such as cellular telephone devices. 
     BACKGROUND OF THE INVENTION 
     Conventionally, a cellular telephone device as a communication terminal can communicate with other communication terminals by way of infrared communication, Bluetooth (registered trademark) and the like as a communication method that is different from a communication method utilizing a predetermined communication network. For example, a communication terminal can directly transmit information to another communication terminal by way of infrared communication or Bluetooth without using any communication network. In a case of utilizing infrared communication, infrared communication units disposed in the plurality of communication terminals are arranged adjacently to one another, and as a result, information can be easily transmitted or received; therefore, personal information such as profiles of the user and friends are easily transmitted or received. 
     Here, for example, a radio communication device has been proposed that transmits scrambled data when personal information is transmitted through communication utilizing Bluetooth (for example, see Patent Document 1).
     Patent Publication 1: Japanese Unexamined Patent Application, No. 2003-37592   

     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, in the invention of Patent Document 1, although private information can be prevented from being leaked to an outside third party, if the personal information is different from that of a sender, it is not possible to suppress transmission of the personal information in a state of having no approval from the person to whom the personal information belongs (or against the person&#39;s intention), or to suppress continuation of a state in which the destination of the personal information is unknown. 
     An object of the present invention is to provide a communication terminal that can suppress transmission of personal information against the intention of the person to whom the personal information belongs. 
     Another object of the present invention is to provide a communication terminal that can suppress continuation of a state in which the destination of personal information is unknown to the person to whom the personal information belongs. 
     Yet another object of the present invention is to provide a communication system including such a communication terminal. 
     Means for Solving the Problems 
     The present invention relates to a communication terminal, including: at least a storage unit, a control unit and a communication unit, in which the storage unit stores first information; the control unit creates information to be transmitted to a second communication terminal different from a first communication terminal; in a case in which the created information includes at least a part of the first information, the control unit transmits a request for transmission permission of the created information to the first communication terminal via the communication unit; and in a case in which a response to the request for transmission permission of the created information is obtained, the control unit transmits the created information to the second communication terminal via the communication unit. 
     Moreover, it is preferable for the first information to include: first identification information corresponding to the first communication terminal; and first associated information associated with the first identification information. 
     In addition, it is preferable for the communication unit to include a first communication unit that performs communication by way of a first communication method for communicating with communication terminals without a communication network, and a second communication unit that performs communication by way of a second communication method for communicating with the communication terminals via the communication network, in which the control unit performs control such that the second communication unit is used preferentially to the first communication unit for communication with the first communication terminal. 
     Furthermore, the present invention relates to a communication terminal, including at least: a storage unit; a control unit; and a communication unit, in which the storage unit stores first information including first identification information corresponding to a first communication terminal, and first associated information associated with the first identification information; the communication unit includes a first communication unit that performs communication by way of a first communication method for communicating with communication terminals without a communication network, and a second communication unit that performs communication by way of a second communication method for communicating with the communication terminals via the communication network; in a case in which the first information is selected to be transmitted by way of the first communication method to a second communication terminal different from the first communication terminal, the control unit transmits a request for transmission permission to the first communication terminal by way of the second communication method different from the first communication method; and in a case in which a response to the request for transmission permission is obtained by way of the first communication method, the control unit transmits the first information to the second communication terminal by way of the second communication method. 
     Moreover, it is preferable for, in a case in which a period of time since the communication unit transmitted information for requesting a reply exceeds a predetermined period of time, the control unit not to permit transmission of a part or all of the first information to the second communication terminal. 
     In addition, the present invention relates to a communication terminal, including at least: a storage unit; a control unit; and a communication unit, in which the storage unit stores first information including first identification information and first associated information associated with the first identification information; in a case in which the first information is selected as information to be transmitted to a second communication terminal, the control unit transmits a request for transmission permission to a first communication terminal via the communication unit; the control unit measures a period of time until obtaining a response to the request for transmission permission; in a case in which the period of time until obtaining the response exceeds the predetermined period of time, the control unit determines that the transmission permission has not been obtained; in a case in which the transmission permission has been obtained before the period of time until obtaining the response exceeds the predetermined period of time, the control unit transmits the first information via the communication unit; and after determining that the transmission permission has not been obtained, the control unit transmits first encryption information encrypted from the first information to the second communication terminal via the communication unit. 
     Furthermore, the present invention relates to a communication system including: a first communication terminal; a main communication terminal that can transmit first identification information and first associated information associated with the first communication terminal to a communication terminal different from the first communication terminal; and a second communication terminal that can receive the first identification information and the first associated information transmitted from the main communication terminal, in which the main communication terminal includes at least a storage unit, a control unit and a communication unit; the storage unit stores first information including the first identification information corresponding to the first communication terminal, and the first associated information associated with the first identification information; in a case in which the first information is selected as information to be transmitted to the second communication terminal, the control unit transmits a request for transmission permission of the first information to the first communication terminal via the communication unit; and in a case in which a response to the request for transmission permission is obtained, the control unit transmits the first information to the second communication terminal via the communication unit. 
     Moreover, the present invention relates to a communication system including: a first communication terminal; a main communication terminal that can transmit first identification information and first associated information associated with the first communication terminal to a communication terminal different from the first communication terminal; and a second communication terminal that can receive the first identification information and the first associated information transmitted from the main communication terminal, in which the main communication terminal includes at least a storage unit, a control unit and a communication unit; the storage unit stores first information including the first identification information and the first associated information associated with the first identification information; the communication unit includes a first communication unit that performs communication by way of a first communication method for communicating with communication terminals without a communication network, and a second communication unit that performs communication by way of a second communication method for communicating with the communication terminals via the communication network; in a case in which the first information is selected to be transmitted to the second communication terminal by way of the first communication method, the control unit transmits a request for transmission permission of the first information to the first communication terminal via the communication unit; and in a case in which a response to the request for transmission permission is obtained by way of the second communication method, the control unit transmits the first information to the second communication terminal by way of the first communication method. 
     In addition, the present invention relates to a communication system including: a first communication terminal that can transmit predetermined decryption key information; a main communication terminal that can transmit first identification information and first associated information associated with the first communication terminal, or encryption information encrypted from the first associated information, to a second communication terminal different from the first communication terminal; and the second communication terminal that can receive the first identification information and the first associated information or the encryption information transmitted from the main communication terminal, in which the main communication terminal includes at least a storage unit, a control unit and a communication unit; the storage unit stores first information including the first identification information and the first associated information associated with the first identification information; in a case in which the first information is selected as information to be transmitted to the second communication terminal, the control unit transmits a request for transmission permission to the first communication terminal via the communication unit; the control unit measures a period of time until obtaining a response to the request for transmission permission from the first communication terminal; in a case in which the period of time until obtaining the response to the request for transmission permission from the first communication terminal exceeds the predetermined period of time, the control unit determines that the transmission permission has not been obtained; in a case in which the transmission permission is obtained before the period of time exceeds the predetermined period of time until obtaining the response, the control unit transmits the first information via the communication unit; and after determining that the transmission permission has not been obtained, the control unit transmits first encryption information encrypted from the first information to the second communication terminal via the communication unit. 
     Furthermore, the present invention relates to a communication system including: a first communication terminal that can transmit decryption key information; a main communication terminal that can transmit encryption information encrypted from a part or all of first identification information corresponding to the first communication terminal and first associated information associated with the first identification information to a second communication terminal different from the first communication terminal; the second communication terminal that can receive the encryption information transmitted from the main communication terminal; and a server that can receive the decryption key information transmitted from the first communication terminal, and can transmit the decryption key information to the second communication terminal, in which the main communication terminal includes at least a main communication terminal side storage unit, a main communication terminal side control unit and a main communication unit; the main communication terminal side storage unit stores first information including first identification information corresponding to the first communication terminal, and first associated information associated with the first identification information, as well as second information including second identification information corresponding to the second communication terminal, and second associated information associated with the second identification information; in a case in which the first information is selected as information to be transmitted to the second communication terminal, the main communication terminal side control unit encrypts the first information to generate encryption information; the main communication terminal side control unit requests permission for transmitting the encryption information to the second communication terminal via the main communication unit; the main communication terminal side control unit transmits, to the server via the main communication unit, first notification information including, notification information for notifying of the fact that the first information has been transmitted to the second communication terminal, the first identification information, and the second identification information; the server includes at least a server side storage unit, a server side control unit and a server communication unit; the server side storage unit can store the first identification information and the second identification information included in the first notification information thus received, and the decryption key information transmitted from the first communication terminal; in a case in which the first notification information is received, the server side control unit transmits second notification information, which includes notification information for notifying of the fact that the first information has been transmitted from the main communication terminal to the second communication terminal, and the second identification information stored in the server side storage unit, to the first communication terminal identified by way of the first identification information stored in the server side storage unit, via the server communication unit; the first communication terminal includes at least a first communication terminal side storage unit, a first communication terminal side control unit and a first communication terminal side communication unit; and the first communication terminal side storage unit stores the first identification information, the second identification information included in the second notification information received by the first communication terminal side communication unit, and the decryption key information. 
     Moreover, the present invention relates to a communication system including: a first communication terminal that can transmit decryption key information; a main communication terminal that can transmit encryption information, which is encrypted from first information including first identification information corresponding to the first communication terminal and first associated information associated with the first identification information, to a second communication terminal different from the first communication terminal; the second communication terminal that can receive the encryption information transmitted from the main communication terminal; and a server that can receive the decryption key information transmitted from the first communication terminal, and can transmit the decryption key information to the second communication terminal, in which the main communication terminal includes at least a storage unit, a control unit and a communication unit; the storage unit stores the first information and second information including second identification information corresponding to the second communication terminal and second associated information associated with the second identification information; in a case in which the first information is selected as information to be transmitted to the second communication terminal, the control unit generates encryption information; the control unit transmits a request for transmission permission of the encryption information to the second communication terminal via the communication unit by way of a first communication method; the control unit transmits first notification information, which includes notification information for notifying of the fact that the first information has been transmitted to the second communication terminal, the first identification information and the second identification information, to the server by way of a second communication method different from the first communication method; the server includes at least a server side storage unit, a server side control unit and a server communication unit; the server side storage unit can store the first identification information and the second identification information included in the first notification information received by way of the second communication method, and the decryption key information transmitted from the first communication terminal; in a case in which the first notification information is received by way of the second communication method, the server side control unit transmits second notification information, which includes notification information for notifying of the fact that a part or all of the first identification information and the first associated information has been transmitted from the main communication terminal to the second communication terminal, and the second identification information stored in the server side storage unit, to the first communication terminal identified by way of the first identification information stored in the server side storage unit, by way of the second communication method; the first communication terminal includes at least a first communication terminal side storage unit; and the first communication terminal side storage unit stores the first identification information, the second identification information included in the second notification information received by way of the second communication method, and the decryption key information. 
     In addition, it is preferable for the first communication terminal to include: a first communication terminal side second communication unit that can communicate by way of the second communication method; and a first communication terminal side decryption key information transmission unit that causes the first communication terminal side second communication unit to transmit the decryption key information stored in the first communication terminal side storage unit to the server, in a case in which the first communication terminal side second communication unit receives the second notification information; and the second communication terminal includes: a second communication terminal side first communication unit that performs communication by way of the first communication method; a second communication terminal side second communication unit that performs communication by way of the second communication method different from the first communication method; a second communication terminal side storage unit that stores the encryption information received by the second communication terminal side first communication unit; a second communication terminal side decryption key information request unit that causes the second communication terminal side second communication unit to transmit first request information for requesting the decryption key information to the server; and a decryption processing unit that decrypts the encryption information stored in the second communication terminal side storage unit, based on a decryption key included in the decryption key information transmitted from the server, in which the server includes: a server side second communication unit that can communicate by way of the second communication method; and a server side decryption key information transmission unit that causes the server side second communication unit to transmit the decryption key information stored in the server side storage unit to the second communication terminal identified by way of the second identification information stored in the server side storage unit, in a case in which the server side second communication unit receives the first request information. 
     Furthermore, it is preferable for the server to include: a server side determination unit that determines whether the decryption key information is stored in the server side storage unit, in a case in which the server side second communication unit receives the first request information; and a server side decryption key information request unit that causes the server side second communication unit to transmit second request information for requesting transmission of the encryption information to the first communication terminal, in a case in which the server side determination unit determines that the encryption information is not stored in the server side storage unit. 
     Moreover, it is preferable for the first communication terminal to include a non-permission information transmission unit that causes the first communication terminal side second communication unit to transmit, to the server, non-permission information for not permitting transmission of the decryption key information stored in the first communication terminal side storage unit to the second communication terminal; the server to include a first erasing instruction information transmission unit that causes the server side second communication unit to transmit first erasing instruction information, which includes an instruction to erase the encryption information stored in the second communication terminal side storage unit, to the second communication terminal, in a case in which the server side second communication unit receives the non-permission information; and the second communication terminal to include a second communication terminal side erasing unit that erases the encryption information stored in the second communication terminal side storage unit, in a case in which the second communication terminal side second communication unit receives the first erasing instruction information. 
     In addition, it is preferable for the server to include a server side erasing unit that erases the decryption key information stored in the server side storage unit, in a case in which the server side second communication unit receives the non-permission information. 
     Furthermore, it is preferable for the second communication terminal to include a second communication terminal side timing unit that measures a period of time since the second communication terminal side first communication unit received the encryption information, and in a case in which the period of time measured by the second communication terminal side timing unit has passed a predetermined period of time, the second communication terminal side erasing unit erases the encryption information stored in the second communication terminal side storage unit. 
     Moreover, it is preferable for the main communication terminal to include: a reply request unit that causes the communication unit to transmit reply request information for requesting a reply regarding whether transmission of the first information is permitted, to the first communication terminal identified by way of the first identification information, in a case in which the selected information is the first information; a timing unit that measures a period of time since the communication unit transmitted the reply request information; a first transmission permission unit that does not permit the communication unit to transmit the first information to the second communication terminal in a case in which the period of time measured by the timing unit exceeds the predetermined period of time, and permits the communication unit to transmit the first information to the second communication terminal in a case in which the communication unit receives a permission reply for permitting transmission of the first information from the first communication terminal before the period of time measured by the timing unit exceeds the predetermined period of time; and an encryption processing unit that encrypts the first information to generate the encryption information, and in a case in which the first transmission permission unit does not permit the communication unit to transmit the first information to the second communication terminal, the encryption processing unit performs encryption processing on the first information. 
     In addition, the present invention relates to a communication system, including: a first communication terminal that can be identified by way of first identification information, and can transmit first decryption key information for enabling decryption of first encryption information that is generated by encrypting the first identification information; a second communication terminal that can be identified by way of second identification information, and can transmit second decryption key information for enabling decryption of second encryption information that is generated by encrypting second associated information associated with the second identification information; a main communication terminal that can transmit the first encryption information to the second communication terminal, and can transmit the second encryption information to the first communication terminal, in which the main communication terminal includes at least a main communication terminal side storage unit and a main communication terminal side control unit; the main communication terminal side storage unit stores the first identification information and the second associated information; in a case in which the first identification information is selected as information to be transmitted to the second communication terminal, the main communication terminal side control unit performs control such that the first encryption information generated by encrypting the first identification information is transmitted to the second communication terminal, and performs control such that the second encryption information generated by encrypting the second associated information is transmitted to the first communication terminal; the first communication terminal includes at least a first communication terminal side storage unit and a first communication terminal side control unit; the first communication terminal side storage unit stores the first decryption key information; in a case in which the second encryption information is received from the main communication terminal, the first communication terminal side control unit performs control such that the first decryption key information stored in the first communication terminal side storage unit can be transmitted to the second communication terminal; the second communication terminal includes at least a second communication terminal side storage unit and a second communication terminal side control unit; the second communication terminal side storage unit stores the second decryption key information; and in a case in which the second communication terminal side control unit has performed control such that the first encryption information received from the main communication terminal is decrypted with the first decryption key information received from the first communication terminal, the second communication terminal side control unit performs control such that the second decryption key information stored in the second communication terminal side storage unit is transmitted to the first communication terminal. 
     Furthermore, the present invention relates to a communication system, including: a first communication terminal that can be identified by way of first identification information; a second communication terminal that can be identified by way of second identification information; a main communication terminal that can transmit first encryption information to the second communication terminal, and can transmit second encryption information to the first communication terminal; and a server that can transmit first decryption key information for enabling decryption of the first encryption information generated by encrypting the first identification information, and can transmit second decryption key information for enabling decryption of the second encryption information generated by encrypting second associated information associated with the second identification information, in which the main communication terminal includes at least a main communication terminal side storage unit, a main communication terminal side control unit and a communication unit; the main communication terminal side storage unit stores the first identification information and the second associated information; in a case in which the first identification information is selected as information to be transmitted to the second communication terminal, the main communication terminal side control unit transmits the first encryption information generated by encrypting the first identification information to the second communication terminal via the communication unit, and transmits the second encryption information generated by encrypting the second associated information to the first communication terminal via the communication unit; the first communication terminal includes at least a first communication terminal side storage unit and a first communication terminal side control unit; the first communication terminal side storage unit stores the first decryption key information; in a case in which the second encryption information is received from the main communication terminal, the first communication terminal side control unit performs control such that the first decryption key information stored in the first communication terminal side storage unit can be transmitted to the server; the second communication terminal includes at least a second communication terminal side storage unit, a second communication terminal side control unit and a second communication unit; the second communication terminal side storage unit stores the second decryption key information; in a case in which the first encryption information is received from the main communication terminal, the second communication terminal side control unit transmits the second decryption key information stored in the second communication terminal side storage unit to the server via the second communication unit; the server includes at least a server side control unit and a server communication unit; and in a case in which the first decryption key information is received from the first communication terminal, and the second decryption key information is received from the second communication terminal, the server side control unit transmits the second decryption key information to the first communication terminal via the server communication unit, and transmits the first decryption key information to the second communication terminal via the server communication unit. 
     Effects of the Invention 
     According to the present invention, it is possible to provide a communication terminal that can suppress the transmission of personal information against the intention of the person to whom the personal information belongs. 
     Moreover, according to the present invention, it is possible to provide a communication terminal that can suppress the continuation of a state in which the destination of personal information is unknown to the person to whom the personal information belongs. 
     In addition, the present invention can provide a communication system including such a communication terminal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating an overview of a communication system S including a main cellular telephone device  1 ; 
         FIG. 2  is a perspective view showing an appearance of the main cellular telephone device  1  in an opened state; 
         FIG. 3  is a circuit block diagram illustrating a circuit configuration of the main cellular telephone device  1  according to a first embodiment; 
         FIG. 4  is a functional block diagram illustrating a functional configuration of the main cellular telephone device  1  according to the first embodiment; 
         FIG. 5  is a sequence diagram showing operations in Example 1-1 relating to the communication system of the first embodiment; 
         FIG. 6  is an example of reply request mail in Example 1-1; 
         FIG. 7  is a sequence diagram showing operations in Example 1-2 relating to the communication system of the first embodiment; 
         FIG. 8  is an example of non-permission notification mail in Example 1-2; 
         FIG. 9  is a functional block diagram illustrating a functional configuration of a main cellular telephone device  1 A according to a second embodiment; 
         FIG. 10  is a functional block diagram illustrating a functional configuration of a first cellular telephone device A 2  according to the second embodiment; 
         FIG. 11  is a functional block diagram illustrating a functional configuration of a second cellular telephone device B 2  according to the second embodiment; 
         FIG. 12  is a sequence diagram showing operations in Example 2-1 relating to the communication system of the second embodiment; 
         FIG. 13  is an example of encryption information transmission completion notification mail in Examples 2-1 and 2-2; 
         FIG. 14  is a sequence diagram showing operations in Example 2-2 relating to the communication system of the second embodiment; 
         FIG. 15  is a sequence diagram showing operations in Example 2-3 relating to the communication system of the second embodiment; 
         FIG. 16  is an example of encryption information transmission completion notification mail in Example 2-3; 
         FIG. 17  is a functional block diagram illustrating a functional configuration of a main cellular telephone device  1 B according to a third embodiment; 
         FIG. 18  is a functional block diagram illustrating a functional configuration of a first cellular telephone device A 3  according to the third embodiment; 
         FIG. 19  is a sequence diagram showing operations in Example 3 relating to the communication system of the third embodiment; 
         FIG. 20  is an example of data transmission completion notification mail in Example 3; 
         FIG. 21  is a flowchart showing operations in a case in which the first identification/associated information includes the transmission number-of-times information and the restricted number-of-times information; 
         FIG. 22  is a diagram illustrating an overview of the communication system S including a main cellular telephone device  1 D; 
         FIG. 23  is a perspective view showing an appearance of the main cellular telephone device  1 D in the opened state; 
         FIG. 24  is a circuit block diagram illustrating a circuit configuration of the main cellular telephone device  1 D according to a fourth embodiment; 
         FIG. 25  is a functional block diagram illustrating a functional configuration of the main cellular telephone device  1 D according to the fourth embodiment; 
         FIG. 26  is a functional block diagram illustrating a functional configuration of a first cellular telephone device A 4  according to the fourth embodiment; 
         FIG. 27  is a functional block diagram illustrating a functional configuration of a second cellular telephone device B 4  according to the fourth embodiment; 
         FIG. 28  is a functional block diagram illustrating a functional configuration of a server W according to the fourth embodiment; 
         FIG. 29  is a sequence diagram showing operations in Example 4-1 relating to the communication system S of the fourth embodiment; 
         FIG. 30  is an example of reply request mail in Example 4-1; 
         FIG. 31  is an example of second notification information mail in Example 4-1; 
         FIG. 32  is a sequence diagram showing operations in Example 4-2 according to the communication system S of the fourth embodiment; 
         FIG. 33  is an example of second request information mail in Example 4-2; 
         FIG. 34  is an example of third notification information mail in Example 4-2; 
         FIG. 35  is a sequence diagram showing operations in Example 4-3 relating to the communication system S of the fourth embodiment; 
         FIG. 36  is a sequence diagram showing operations in Example 4-4 relating to the communication system S of the fourth embodiment; 
         FIG. 37  is a sequence diagram showing operations in Example 4-5 relating to the communication system S of the fourth embodiment; 
         FIG. 38  is a functional block diagram illustrating a functional configuration of the main cellular telephone device  1 F according to a fifth embodiment; 
         FIG. 39  is a functional block diagram illustrating a functional configuration of a first cellular telephone device A 5  according to the fifth embodiment; 
         FIG. 40  is a functional block diagram illustrating a functional configuration of a second cellular telephone device B 5  according to the fifth embodiment; 
         FIG. 41  is a sequence diagram showing operations relating to the communication system S of the fifth embodiment; 
         FIG. 42  is a functional block diagram illustrating a functional configuration of a server W 1  according to a sixth embodiment; 
         FIG. 43  is a sequence diagram showing operations relating to the communication system S of the sixth embodiment; and 
         FIG. 44  is a diagram showing address book information to be added to transmitted information. 
     
    
    
     EXPLANATION OF REFERENCE NUMERALS 
     
         
         
           
               1 ,  1 A,  1 B,  1 C,  1 D,  1 E,  1 F main cellular telephone device (main communication terminal) 
             A, A 1 , A 2 , A 3 , A 4 , A 5 , A 6  first cellular telephone device (first communication terminal) 
             B, B 1 , B 2 , B 3 , B 4 , B 5 , B 6  second cellular telephone device (second communication terminal) 
             S communication system 
             N communication network 
             W, W 1  server 
               20  first communication unit (communication unit) 
               20 B second communication terminal side first communication unit 
               21 ,  21 A,  21 B display unit 
               80 ,  80 A timer (timing unit) 
               80 B timer (second communication terminal side timing unit) 
               45 ,  45 A,  45 B,  45 C,  45 D,  45 E,  45 F CPU (control unit) 
               121 ,  221 ,  321 ,  421 ,  521  selection unit (information creation unit) 
               122 ,  222 ,  322 ,  422 ,  522  reply request unit 
               123 ,  223 ,  323 ,  423 ,  523  first communication permission unit, first transmission permission unit 
               124  notification unit 
               131 ,  231 ,  331 ,  431 ,  531  first identification/associated information storage unit (first storage unit) 
               134 ,  234 ,  334 ,  434 ,  534  second identification/associated information storage unit (second storage unit) 
               200  second communication unit (communication unit) 
               200 A first communication terminal side second communication unit 
               200 B second communication terminal side second communication unit 
               224 ,  424  encryption processing unit 
               225  second communication permission unit 
               227  third communication permission unit 
               236  third information storage unit (third storage unit) 
               241  first communication terminal side third communication permission unit 
               242  first communication terminal side notification unit 
               251 ,  437 ,  537  decryption key information storage unit 
               262  decryption key request unit 
               263  erasing unit 
               324  fourth communication permission unit 
               341  comparing unit 
               342  extracting unit 
               343  display control unit 
               424  encryption processing unit 
               425  encryption information transmission permission unit 
               426  first notification information transmission unit 
               436  third information storage unit (third storage unit) 
               441  first communication terminal side decryption key information transmission unit 
               442 ,  542  non-permission information transmission unit 
               451  first communication terminal side first storage unit 
               452  first communication terminal side second storage unit 
               453 ,  552  first communication terminal side decryption key information storage unit 
               462  second communication terminal side decryption key information request unit 
               461  decryption processing unit 
               463  second communication terminal side erasing unit 
               471  second communication terminal side encryption information storage unit 
               571  second communication terminal side decryption key information storage unit 
               544  first communication terminal side decryption processing unit 
               561  second communication terminal side decryption processing unit 
               911  second notification information transmission unit 
               912 ,  1011  server side decryption key information transmission unit 
               913 ,  1012  server side determination unit 
               914  server side decryption key information request unit 
               915  third notification information transmission unit 
               916  fourth notification information transmission unit 
               917  server side erasing unit 
               918  first erasing instruction information transmission unit 
               941  server side first storage unit 
               942  server side second storage unit 
               943  server side decryption key information storage unit 
               960  server side second communication unit (server side communication unit) 
           
         
       
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention are hereinafter described with reference to the drawings. First, with reference to  FIG. 1 , a description is provided for a communication system S that includes a main cellular telephone device  1  as a (main) communication terminal, a first cellular telephone device A 1  as a first communication terminal, and a second cellular telephone device B 1  as a second communication terminal.  FIG. 1  is a diagram illustrating an overview of the communication system S including the main cellular telephone device  1 . 
     As shown in  FIG. 1 , the communication system S includes the main cellular telephone device  1 , the first cellular telephone device A 1 , and the second cellular telephone device B 1 . Here, users of the first cellular telephone device A 1 , the main cellular telephone device  1 , and the second cellular telephone device B 1  are referred to as a user X, a user Y and a user Z, respectively. 
     The main cellular telephone device  1  can transmit and receive predetermined information to and from the first cellular telephone device A 1  and the second cellular telephone device B 1  by way of wireless communication (second communication method) via a communication network N. In addition, the main cellular telephone device  1  can transmit and receive predetermined information to and from the second cellular telephone device B 1  by way of infrared communication (first communication method). 
     In a case in which the main cellular telephone device  1  transmits predetermined information to the second cellular telephone device B 1  by way of infrared communication, the main cellular telephone device  1  is disposed adjacent to the second cellular telephone device B 1 . On the other hand, the first cellular telephone device A 1  is disposed at a position separated from the main cellular telephone device  1  and the second cellular telephone device B 1 . In other words, the main cellular telephone device  1  is disposed at a position in which it is not possible to directly confirm whether personal information of the user X may be transmitted to the user (the user X) of the first cellular telephone device A 1 . Even in this state, the communication system S in the present embodiment achieves an effect. 
     Next, a detailed description is provided for the configuration of the main cellular telephone device  1  according to the communication system S of the first embodiment with reference to  FIG. 2 .  FIG. 2  is a perspective view showing an appearance of the main cellular telephone device  1  in an opened state. 
     As shown in  FIG. 2 , the main cellular telephone device  1  includes an operation unit side body  2  and a display unit side body  3  as its bodies. The operation unit side body  2  and the display unit side body  3  are connected so as to be openable and closable via a connecting portion  4  including a hinge mechanism. More specifically, an upper end portion of the operation unit side body  2  and a lower end portion of the display unit side body  3  are connected via the connecting portion  4  including the hinge mechanism. As a result, the main cellular telephone device  1  is configured such that the operation unit side body  2  and the display unit side body  3  connected via the hinge mechanism can be relatively moved. In other words, the main cellular telephone device  1  can be transformed between a state in which the operation unit side body  2  and the display unit side body  3  are opened (the opened state), and a state in which the operation unit side body  2  and the display unit side body  3  are folded (a closed state). Here, the closed state refers to a state in which both bodies are disposed so as to be mutually superimposed. The opened state refers to a state in which both bodies are disposed so as not to be mutually superimposed. 
     An outer face of the operation unit side body  2  is configured with a front case  2   a  and a rear case  2   b . The operation unit side housing  2  is configured to expose, on the front case  2   a  side, both an operation key set  11  as an input unit and a microphone  12  to which sound produced by the user of the main cellular telephone device  1  during a phone call is input. 
     The operation key set  11  is configured with: function setting operation keys  13  for operating various functions such as for various settings, a telephone number directory function and a mail function; input operation keys  14  for inputting digits of a telephone number, characters for mail, etc.; and a selection operation key  15  for performing selection of the various operations and scrolls up, down, left and right. Predetermined functions are assigned (key assignment) to each key configuring the operation key set  11  in accordance with the opened/closed state of the operation unit side body  2  and the display unit side body  3 , various modes, and the type of application that is running. An operation corresponding to a function assigned to each key is executed by the user depressing each key. 
     The microphone  12  is disposed on an outer end side that is opposite to the connecting portion  4  side of the operation unit side body  2  in a longitudinal direction. In other words, the microphone  12  is disposed on one outer end side of the main cellular telephone device  1  in the opened state. 
     An interface (not illustrated) for communicating with an external device (for example, a host device) is disposed on one side face of the operation unit side body  2 . Side keys to which predetermined functions are assigned, and an interface (not illustrated) where external memory is inserted and removed are disposed on another side face of the operation unit side body  2 . The interfaces are covered by caps. When not in use, an interface is covered by the respective cap. 
     An outer surface of the display unit side body  3  is configured with a front case  3   a  and a rear case  3   b . On the front case  3   a  of the display unit side body  3 , a display unit  21  for displaying a variety of information, and a speaker  22  as a receiver that outputs sound of the other party of a phone call are disposed so as to be exposed to the outside. Here, the display unit  21  is configured with a liquid crystal display panel, a drive circuit that drives the liquid crystal display panel, and a light source unit such as a backlight that irradiates light from the back face side of the liquid crystal display panel. 
     Next, a circuit configuration of the main cellular telephone device  1  is described with reference to  FIG. 3 .  FIG. 3  is a circuit block diagram illustrating a circuit configuration of the main cellular telephone device  1  according to the first embodiment. 
     As shown in  FIG. 3 , the operation unit side body  2  of the main cellular telephone device  1  includes: a radio communication unit  200  as a second communication unit; an operation unit  101  as an input unit; the microphone  12 ; an LCD control unit  42 ; a sound processing unit  43 ; memory  44 ; a CPU  45 ; a power supply unit  46 ; a control IC  47 ; and a timer  80  as a timing unit. In addition, the display unit side body  3  of the main cellular telephone device  1  includes: the display unit  21 , the speaker  22 , a driver IC  25 , and an infrared communication unit  20  as a first communication unit. 
     It should be noted that a communication unit conforming to, for example, Bluetooth (IEEE 802.15.1, registered trademark) may be provided in place of the infrared communication unit  20 , or in addition to the infrared communication unit  20 . 
     The radio communication unit  200  includes an antenna unit  90  and a communication processing unit  201 . 
     The radio communication unit  200  is configured so as to be capable of externally transmitting and receiving predetermined information. The radio communication unit  200  performs communication by way of a method using radio waves (the second communication method) that is different from infrared communication. The radio communication unit  200  can transmit predetermined information to the first cellular telephone device A via the predetermined communication network N (see  FIG. 1 ). The radio communication unit  200  can, for example, transmit predetermined information as a text of E-mail or as an attachment to E-mail. 
     The radio communication unit  200  can, for example, transmit information such as: address information (first identification information) such as a mail address and a telephone number; profile information (first associated information) such as a name, an address and a profile; information for prompting a user (the user Z) of another cellular telephone device to transmit a reply of permitting transmission of predetermined information; information for permitting transmission of predetermined information; and decryption key information including a decryption key for decrypting predetermined encryption information. 
     Based on a predetermined communication method (for example, CDMA (Code Division Multiple Access) 2000 — 1x or the like), the antenna unit  90  performs communication by phone, mail or the like with other communication terminals via a base station. 
     The communication processing unit  201  is configured with a transmitting circuit that performs transmission processing, and a receiving circuit that performs reception processing. The communication processing unit  201  performs demodulation processing by the receiving circuit on a signal received via the antenna unit  90 , and transmits the signal thus processed to the CPU  45 . In addition, the communication processing unit  201  performs modulation processing by the transmitting circuit on the signal transmitted from the CPU  45 , and transmits the signal to a base station via the antenna unit  90 . 
     The operation unit  101  is configured to include the operation key set  11 . 
     The LCD control unit  42  performs predetermined image processing on input image data in accordance with control by the CPU  45 , and outputs the image data, on which the image processing has been performed, to the driver IC  25 . The driver IC  25  stores the image data being input from the LCD control unit  42  in frame memory, and outputs the image data stored in the frame memory to the display unit  21  at predetermined timing. 
     The display unit  21  displays predetermined characters and images based on the data that is input from the driver IC  25 . 
     The memory  44  stores predetermined data. More specifically, the memory  44  has various storage units that store a variety of data and application programs for operating various functions (see  FIG. 4 ). Details about the memory  44  will be described later. 
     The CPU  45  controls the entirety of the main cellular telephone device  1 . The CPU  45  performs predetermined control of the radio communication unit  200 , the LCD control unit  42  and the sound processing unit  43 , in particular. Details about the CPU  45  will be described later. 
     In accordance with control by the CPU  45 , the sound processing unit  43  performs predetermined sound processing on a signal transmitted from the communication processing unit  201 , and outputs the signal on which the sound processing has been performed to the speaker  22 . Based on a signal transmitted from the sound processing unit  43 , the speaker  22  outputs sound externally. Moreover, in accordance with control by the CPU  45 , the sound processing unit  43  performs predetermined processing on a signal that is input from the microphone  12 , and outputs the signal thus processed to the communication processing unit  201 . The communication processing unit  201  performs predetermined processing on the signal that is input from the sound processing unit  43 , and outputs the signal thus processed to the antenna unit  90 . 
     The power supply unit  46  is configured to include a battery (not illustrated). The battery is composed of a lithium-ion battery having predetermined capacity. 
     The control IC  47  converts a power supply voltage, which is supplied from the power supply unit  46 , into a predetermined power supply voltage, and supplies the power supply voltage thus converted to each unit (for example, the CPU  45  and the like) of the main cellular telephone device  1 . 
     The timer  80  has a timing function. The timer  80  is configured to measure a period of time that elapses from a predetermined time, and to be capable of outputting a predetermined signal (a time-up signal) to the CPU  45  when the elapsed period of time exceeds a predetermined period of time. For example, the timer  80  measures a period of time since the radio communication unit  200  transmitted information for requesting a reply. 
     The infrared communication unit  20  is disposed in the display unit side body  3  in the vicinity of the end portion that is opposite to the connecting portion  4 . The infrared communication unit  20  is configured to be compatible with the IrDA (Infrared Data Association) standard. The infrared communication unit  20  is configured to be capable of outputting a predetermined signal externally. The infrared communication unit  20  is configured to be capable of outputting information stored in the memory  44  and the like, which will be described later. 
     The infrared communication unit  20  transmits predetermined information stored in the memory  44  to the second cellular telephone device B that is disposed outside and includes a similar infrared communication unit  20 B. The infrared communication unit  20  can transmit and receive information by way of an infrared communication method (the first communication method) using infrared light, which is a communication method different from that of the radio communication unit  200 . Information transmitted from the communication unit  20  of the main cellular telephone device  1  is received by the communication unit  20 B of the second cellular telephone device B as the second communication terminal. 
     The infrared communication unit  20  can transmit address information and profile information of the user Y of the main cellular telephone device  1 , address information and profile information of the user X of the first cellular telephone device A, etc. Moreover, the infrared communication unit  20  can also transmit and receive encryption information that is profile information or the like on which encryption processing has been performed. 
     In an infrared communication mode that enables infrared communication, the selection operation key  15  is assigned with a function of selecting information (for example, address information and profile information) to be transmitted to another cellular telephone device (for example, the second cellular telephone device B) as the second communication terminal, and a function of determining transmission of the information thus selected. 
     Next, functions of the main cellular telephone device  1  according to the first embodiment are described in detail with reference to  FIG. 4 .  FIG. 4  is a functional block diagram illustrating a functional configuration of the main cellular telephone device  1  according to the first embodiment. Here, the functional configuration relating to the memory  44  and the functional configuration relating to the CPU  45  are mainly described with reference to  FIG. 4 . 
     The memory  44  includes: a first identification/associated information storage unit  131 , a first selected information storage unit  132 , a reply request information storage unit  133 , a second identification/associated information storage unit  134 , a non-permission notification information storage unit  135 , and a reply information storage unit  136 . 
     The first identification/associated information storage unit  131  stores first identification information corresponding to the first cellular telephone device A 1 , and first associated information that is associated with the first identification information. The first identification information is information corresponding to the first cellular telephone device A 1  or its user (the user X), and is, for example, a mail address, a telephone number (address information) and the like of the user X. The first associated information is information associated with the first identification information, and is, for example, a name, an address, a profile (profile information), a facial photograph and the like of the user X. 
     The first selected information storage unit  132  stores information selected by a selection unit  121  of the CPU  45 , which will be described later. More specifically, the first selected information storage unit  132  stores “a part or all of the first identification information and the first associated information stored in the first identification/associated information storage unit  131 ” selected by the selection unit  121  of the CPU  45 . 
     It should be noted that the “part or all of the first identification information and the first associated information” is hereinafter also referred to as “first identification/associated information”. 
     The reply request information storage unit  133  stores reply request information transmitted by a reply request unit  122  of the CPU  45 , which will be described later. 
     The second identification/associated information storage unit  134  stores second identification information corresponding to the second cellular telephone device B 1 , and second associated information that is associated with the second identification information. The second identification information is information corresponding to the second cellular telephone device B 1  or its user (the user Z), and is, for example, a mail address, a telephone number (address information) and the like of the user Z. The second associated information is information associated with the second identification information, and is, for example, a name, an address, a profile (profile information), a photograph and the like of the user Z. 
     It should be noted that the “part or all of the second identification information and the second associated information” is hereinafter also referred to as “second identification/associated information”. 
     The non-permission notification information storage unit  135  stores non-permission notification information transmitted by a notification unit  124  of the CPU  45 , which will be described later. 
     The reply information storage unit  136  stores information replied from the first cellular telephone device A 1 . 
     Next, the functional configuration of the CPU  45  is described. The CPU  45  includes the selection unit (information creation unit)  121 , the reply request unit  122 , a first communication permission unit  123 , and the notification unit  124 . 
     It should be noted that the CPU  45  of the main cellular telephone device  1  performs control such that the radio communication unit  200  is preferentially used rather than the infrared communication unit  20 , for communication with the first cellular telephone device A 1 . By performing control in this way, even in a case in which the user (the user X) of the first cellular telephone device A is not present near the user (the user Y) of the main cellular telephone device  1 , communication with the first cellular telephone device A 1  can be performed more reliably by using the radio communication unit  200  via the communication network N. 
     From among the first identification/associated information stored in the first identification/associated information storage unit  131 , the selection unit  121  selects information to be transmitted by the infrared communication unit  20  to the second cellular telephone device B 1 . For example, the selection unit  121  selects a mail address of the user X. The first identification/associated information selected by the selection unit  121  is also referred to as “first selected information”. The selection unit  121  causes the first selected information storage unit  132  of the memory  44  to store the first selected information. 
     In a case in which the information selected by the selection unit  121  is the first identification/associated information, the reply request unit  122  causes the radio communication unit  200  to transmit, to the first cellular telephone device A 1 , information (reply request information) for requesting a reply regarding whether to permit transmission of the first identification/associated information (the first selected information). For example, in a case in which the first selected information is a mail address of the user X, the radio communication unit  200  is caused to transmit, to the first cellular telephone device A 1 , information (reply request information) for requesting a reply regarding whether to permit transmission of the mail address of the user X. 
     In a case in which the radio communication unit  200  receives a permission reply for permitting transmission of the first identification/associated information (the first selected information) that has been returned from the first cellular telephone device A 1 , the first communication permission unit  123  permits the infrared communication unit  20  to transmit the first selected information to the second cellular telephone device B 1 . For example, in a case in which the radio communication unit  200  receives a permission reply for permitting transmission of the mail address of the user X, the infrared communication unit  20  is permitted to transmit the mail address of the user X to the second cellular telephone device B 1 . 
     Moreover, in a case in which a period of time measured by the timer  80  exceeds a predetermined period of time (for example, 5 minutes), the first communication permission unit  123  does not permit transmission of the first identification/associated information (the first selected information) to the second cellular telephone device B 1 . 
     Moreover, in a case in which after the first communication permission unit  123  does not permit transmission of the first identification/associated information (the first selected information, for example, a mail address of the user X), the radio communication unit  200  subsequently receives a permission reply, the first communication permission unit  123  permits transmission of the first selected information to the second cellular telephone device B 1  when the first selected information is selected again by the selection unit  121 . 
     In a case in which a period of time measured by the timer  80  exceeds a predetermined period of time (for example, 5 minutes), and the first communication permission unit  123  does not permit transmission of the first identification/associated information (the first selected information, for example, a mail address of the user X) to the second cellular telephone device B 1 , the notification unit  124  causes the radio communication unit  200  to transmit non-permission notification information to the first cellular telephone device A 1 . The “non-permission notification information” is information for notifying of the fact that the first communication permission unit  123  does not permit transmission of the first selected information (for example, a mail address of the user X) to the second cellular telephone device B 1 . 
     The first cellular telephone device A 1  and the second cellular telephone device B 1  according to the first embodiment have a configuration similar to that of the main cellular telephone device  1  according to the first embodiment, except for the functional configurations of the memory  44  and the CPU  45  as described above. Therefore, the description regarding the main cellular telephone device  1  is appropriately applied to the first cellular telephone device A 1  and the second cellular telephone device B 1 , and descriptions thereof are omitted. 
     Next, a description is provided for operations of the communication system of the first embodiment, which includes the main cellular telephone device  1 , the first cellular telephone device A 1 , and the second cellular telephone device B 1 . Examples 1-1 and 1-2 are hereinafter described as examples relating to the communication system of the first embodiment. Example 1-1 is an example of a case in which permission reply mail is received within a predetermined period of time after transmitting reply request mail. Example 1-2 is an example of a case in which permission reply mail is not received within a predetermined period of time after transmitting reply request mail.  FIG. 5  is a sequence diagram showing operations in Example 1-1 according to the communication system of the first embodiment.  FIG. 6  is an example of the reply request mail in Example 1-1.  FIG. 7  is a sequence diagram showing operations in Example 1-2 according to the communication system of the first embodiment.  FIG. 8  is an example of the non-permission notification mail in Example 1-2. 
     Example 1-1 
     Operations in Example 1-1 are described with reference to  FIGS. 5 and 6 . 
     When the user Y performs an operation to select information to be transmitted to the user Z from among the first identification/associated information, in Step ST 111 , the selection unit  121  of the CPU  45  selects information (the first selected information) to be transmitted to the second cellular telephone device B 1  owned by the user Z from among the first identification/associated information stored in the first identification/associated information storage unit  131  of the memory  44 . In the present example, the first selected information is a mail address of the user X. In addition, the selection unit  121  stores the first selected information in the first selected information storage unit  132  of the memory  44 . 
     In Step ST 112 , in a case in which the first selected information is the first identification/associated information, the reply request unit  122  of the CPU  45  causes the radio communication unit  200  to transmit, to the first cellular telephone device A 1 , information (reply request information) for requesting a reply regarding whether to permit transmission of the first selected information. Here, the reply request information is stored in the reply request information storage unit  133  of the memory  44 . 
     In the present example, the reply request unit  122  transmits mail (reply request mail) for requesting a reply regarding whether to permit transmission of the first selected information (a mail address) to the user X. As shown in  FIG. 6 , this reply request mail includes, for example, a message stating that “Your (the user X&#39;s) mail address will be transmitted to the user Z. Do you approve? OK/NG” for requesting confirmation and reply, and includes a profile of the user Z (for example, “the user Z is a colleague of the user Y”). 
     In Step ST 113 , the timer  80  measures (times) a period of time (elapsed time) since the radio communication unit  200  transmitted the reply request information (reply request mail). 
     When the user X confirms the reply request mail, and performs an operation (selecting “OK”) to transmit a reply (a permission reply) for permitting transmission of the first identification/associated information, in Step ST 114 , the CPU  45 A of the first cellular telephone device A 1  causes the radio communication unit  200 A to transmit permission reply mail. As a result, the radio communication unit  200 A of the first cellular telephone device A 1  transmits the permission reply mail. 
     In a case in which the second cellular telephone device B 1  receives the permission reply mail via the radio communication unit  200  before the elapsed time measured by the timer  80  reaches a predetermined period of time (for example, 5 minutes), in Step ST 115 , the first communication permission unit  123  permits the infrared communication unit  20  to transmit the first identification/associated information selected by the selection unit  121  (the first selected information stored in the first selected information storage unit  132 ) to the second cellular telephone device B 1 . 
     In Step ST 116 , the main cellular telephone device  1  transmits the first identification/associated information (a mail address of the user X) to the second cellular telephone device B 1  via the infrared communication unit  20 . 
     In this way, in Example 1-1, on condition of permission by the user X, the first identification/associated information (a mail address of the user X) is transmitted to the second cellular telephone device B 1  owned by the user Z. 
     It should be noted that, in Example 1-1, in a case in which the first cellular telephone device A 1  transmits reply mail for not permitting transmission of the first identification/associated information, and in a case in which the permission reply mail is not transmitted, the first identification/associated information (a mail address of user X) is not transmitted from the main cellular telephone device  1  to the second cellular telephone device B 1 . 
     Example 1-2 
     Operations in Example 1-2 are described with reference to  FIGS. 7 and 7 . 
     Since Steps ST 121  to ST 123  in Example 1-2 are similar to Steps ST 111  to ST 113  in Example 1-1, respectively, descriptions thereof are omitted. 
     In a case in which permission reply mail is not received from the first cellular telephone device A 1  after the elapsed time measured by the timer  80  exceeds a predetermined period of time (for example, 5 minutes), in Step ST 124 , the timer  80  terminates the timing. 
     When the timer  80  terminates the timing, in Step ST 125 , the first communication permission unit  123  does not permit (does not approve) transmission of the first identification/associated information to the second cellular telephone device B 1 . 
     In addition, when the elapsed time measured by the timer  80  exceeds the predetermined period of time, and the first communication permission unit  123  does not permit transmission of the first identification/associated information to the second cellular telephone device B 1 , in Step ST 126 , the notification unit  124  causes the first cellular telephone device A 1  to transmit non-permission notification information stored in the non-permission notification information storage unit  135  of the memory  44  (information for notifying of the fact that the first communication permission unit does not permit transmission of the first identification/associated information to the second cellular telephone device B 1 ). 
     In the present example, as shown in  FIG. 8 , the notification unit  124  transmits non-permission notification mail (cancellation mail) stating that “Since a reply has not come from you (the user X), transmission of the mail address to the user Z is suspended. If you approve transmission of the mail address to the user Z, please reply as such.” 
     After a predetermined period of time elapses since the non-permission notification mail was transmitted, in Step ST 127 , according to an operation by the user X, the radio communication unit  200  of the first cellular telephone device A 1  transmits a reply (permission reply) for permitting transmission of the first selected information to the second cellular telephone device B 1 , or a reply (non-permission reply) for not permitting transmission of the first selected information to the second cellular telephone device B 1 . In addition, the permission reply or the non-permission reply is received by the radio communication unit  200  of the main cellular telephone device  1 . 
     In Step ST 128 , the permission reply or the non-permission reply received by the main cellular telephone device  1  is stored in the reply information storage unit  136  of the memory  44 . 
     In a case in which transmission of the first identification/associated information is not permitted, and the main cellular telephone device  1  subsequently receives a permission reply, in Step ST 129 , the first communication permission unit  123  permits transmission of the first identification/associated information to the second cellular telephone device B 1  when the first identification/associated information is selected again by the selection unit  121 . 
     In Step ST 130 , the main cellular telephone device  1  transmits the first identification/associated information (a mail address of the user X) to the second cellular telephone device B 1  via the infrared communication unit  20 . 
     In this way, in Example 1-2, even if a permission reply of the user X is not received within a predetermined period of time measured by the timer  80 , so long as a permission reply is subsequently received, the first identification/associated information (a mail address of the user X) is transmitted to the second cellular telephone device B 1  owned by the user Z. 
     It should be noted that, in a case in which the radio communication unit  200  receives a non-permission reply, even if the first identification/associated information is selected again by the selection unit  121 , the first communication permission unit  123  does not permit transmission of the first identification/associated information to the second cellular telephone device B 1 . 
     As described above, according to the first embodiment, only in a case in which permission reply mail is received from the first cellular telephone device A 1  (the user X), the main cellular telephone device  1  (the user Y) transmits the first identification/associated information (a mail address of the user X) to the second cellular telephone device B 1  (the user Z). Therefore, the first identification/associated information that is personal information of the user X can be prevented from being transmitted to the user Z without permission of (against the intention of) the user X. A state in which the destination of personal information is unknown to oneself can be prevented from continuing. 
     Moreover, as in Example 1-2, even if permission reply mail is not received from the first cellular telephone device A 1  (the user X) within a predetermined period of time, so long as permission reply mail is subsequently received, the main cellular telephone device  1  (the user Y) transmits the first identification/associated information (a mail address of the user X) to the second cellular telephone device B 1  (the user Z) without the necessity of asking for permission from the user X again. 
     Next, the communication system S of a second embodiment is described. The communication system S of the second embodiment includes a main cellular telephone device  1 A, a first cellular telephone device A 2 , and a second cellular telephone device B 2 . 
       FIG. 9  is a functional block diagram illustrating a functional configuration of the main cellular telephone device  1 A according to the second embodiment.  FIG. 10  is a functional block diagram illustrating a functional configuration of the first cellular telephone device A 2  according to the second embodiment.  FIG. 11  is a functional block diagram illustrating a functional configuration of the second cellular telephone device B 2  according to the second embodiment.  FIG. 12  is a sequence diagram showing operations in Example 2-1 according to the communication system of the second embodiment.  FIG. 13  is an example of encryption information transmission completion notification mail in Examples 2-1 and 2-2.  FIG. 14  is a sequence diagram showing operations in Example 2-2 according to the communication system of the second embodiment.  FIG. 15  is a sequence diagram showing operations in Example 2-3 according to the communication system of the second embodiment.  FIG. 16  is an example of encryption information transmission completion notification mail in Example 2-3. 
     The functional configuration relating to the memory  44  and the functional configuration relating to the CPU  45  in the main cellular telephone device  1 A are mainly described with reference to  FIG. 9 . Since configurations that are not described in particular are similar to the configurations of the main cellular telephone device  1  in the first embodiment shown in  FIG. 4 , descriptions thereof are omitted. 
     In the main cellular telephone device  1 A according to the second embodiment, the memory  44  includes a first identification/associated information storage unit  231 , a first selected information storage unit  232 , a reply request information storage unit  233 , a second identification/associated information storage unit  234 , an encryption information storage unit  235 , a third information storage unit  236  as a third storage unit, and a decryption key information storage unit  237 . 
     The first identification/associated information storage unit  231 , the first selected information storage unit  232 , the reply request information storage unit  233 , and the second identification/associated information storage unit  234  in the second embodiment are similar to the first identification/associated information storage unit  131 , the first selected information storage unit  132 , the reply request information storage unit  133 , and the second identification/associated information storage unit  134  in the first embodiment, respectively; therefore, descriptions thereof are omitted. 
     The encryption information storage unit  235  stores encryption information generated by an encryption processing unit  224  that will be described later. 
     The third information storage unit  236  stores third information. The third information includes: a plurality of pieces of third identification information corresponding to a plurality of communication terminals, respectively; and a plurality of pieces of third associated information that are associated with the plurality of pieces of third identification information, respectively. 
     The third identification information is, for example, a mail address and a telephone number of a user. The third associated information is, for example, a name, an address and a profile of the user. 
     The decryption key information storage unit  237  stores decryption key information. The decryption key information includes a decryption key for decrypting predetermined encryption information, usable number-of-times restriction information for restricting the number of times the decryption key can be utilized for decryption processing of the encryption information, etc. 
     In the main cellular telephone device  1 A according to the second embodiment, the CPU  45  includes a selection unit  221 , a reply request unit  222 , a first communication permission unit  223 , an encryption processing unit  224 , a second communication permission unit  225 , a second notification unit  226 , and a third communication permission unit  227 . 
     The selection unit  221 , the reply request unit  222  and the first communication permission unit  223  in the second embodiment are similar to the selection unit  121 , the reply request unit  122  and the first communication permission unit  123  in the first embodiment, respectively; therefore, descriptions thereof are omitted. 
     In a case in which a period of time measured by the timer  80  exceeds a predetermined period of time, and thus the first communication permission unit  223  does not permit transmission of the first identification/associated information, the encryption processing unit  224  encrypts the first identification/associated information to generate encryption information. Moreover, the encryption processing unit  224  causes the decryption key information storage unit  237  of the memory  44  to store decryption key information including a decryption key for decrypting this encryption information. 
     The second communication permission unit  225  permits the infrared communication unit  20  to transmit the encryption information generated by the encryption processing unit  224  to the second cellular telephone device B 1 . 
     In a case in which the main cellular telephone device  1 A transmits encryption information to the second cellular telephone device B 2 , the second notification unit  226  causes the radio communication unit  200  to transmit, to the first cellular telephone device A 2 , information for notifying of the fact that encryption information generated by encrypting the first identification/associated information has been transmitted to the second cellular telephone device B 2 . 
     In a case in which encryption information is transmitted to the second cellular telephone device B 2 , and the radio communication unit  200   a  subsequently receives a permission reply from the first cellular telephone device A 2 , the third communication permission unit  227  permits the radio communication unit  200  to transmit the decryption key information including the decryption key for decrypting the encryption information. In addition, the third communication permission unit  227  permits the infrared communication unit  20  to transmit the decryption key information stored in the decryption key information storage unit  237  to the second cellular telephone device B 2 . In addition, the third communication permission unit  227  permits the radio communication unit  200  to transmit the decryption key information stored in the decryption key information storage unit  237  to the first cellular telephone device A 2 . 
     Next, the functional configuration relating to memory  44 A and the functional configuration relating to a CPU  45 A in the first cellular telephone device A 2  according to the second embodiment are mainly described with reference to  FIG. 10 . Since configurations that are not described in particular are similar to the configurations of the main cellular telephone device  1 A in the second embodiment, descriptions thereof are omitted. Moreover, among the configurations of the first cellular telephone device, the configurations similar to the configurations of the main cellular telephone device are denoted by reference numerals with a suffix “A” (for example, the infrared communication unit  20  of the main cellular telephone device is denoted as an infrared communication unit  20 A of the first cellular telephone device). 
     In the first cellular telephone device A 2  according to the second embodiment, the memory  44 A includes a decryption key information storage unit  251 , and a decryption key information transmission information storage unit  252 . 
     The decryption key information storage unit  251  stores decryption key information that is transmitted from the main cellular telephone device  1 A and is received via the radio communication unit  200 A. 
     The decryption key information transmission information storage unit  252  stores decryption key information transmission information that is transmitted to the main cellular telephone device  1 A by a first communication terminal side notification unit  242  of the CPU  45 A, which will be described later. 
     In the first cellular telephone device A 2  according to the second embodiment, the CPU  45 A includes a first communication terminal side third communication permission unit  241  and the first communication terminal side notification unit  242 . 
     The first communication terminal side third communication permission unit  241  permits the radio communication unit  200 A of the first cellular telephone device A 2  to transmit decryption key information stored in the decryption key information storage unit  251  to the second cellular telephone device B 2 . 
     In a case in which the first communication terminal side third communication permission unit  241  transmits decryption key information to the second cellular telephone device B 2 , the first communication terminal side notification unit  242  causes the radio communication unit  200 A to transmit information (decryption key information transmission notification information), to the main communication terminal  1 A, for notifying of the fact that the decryption key information has been transmitted to the second cellular telephone device B 2 . 
     Next, the functional configuration relating to memory  44 B and the functional configuration relating to a CPU  45 B in the second cellular telephone device B 2  according to the second embodiment are mainly described with reference to  FIG. 11 . Since configurations that are not described in particular are similar to the configurations of the main cellular telephone device  1 A in the second embodiment, descriptions thereof are omitted. Moreover, among the configurations of the second cellular telephone device, the configurations similar to the configurations of the main cellular telephone device are denoted by reference numerals with a suffix “B” (for example, the infrared communication unit  20  of the main cellular telephone device is denoted as the infrared communication unit  20 B of the second cellular telephone device). 
     In the second cellular telephone device B 2  according to the second embodiment, a timer  80 B measures a period of time elapsed since the infrared communication unit  20 B received encryption information transmitted from the main communication terminal  1 A. 
     In the second cellular telephone device B 2  according to the second embodiment, the memory  44 B includes a second encryption information storage unit  271  and a decryption key request information storage unit  272 . 
     The second encryption information storage unit  271  stores encryption information that is transmitted from the main cellular telephone device  1 A and is received via the infrared communication unit  20 B. 
     The decryption key request information storage unit  272  stores information for requesting a decryption key from the main cellular telephone device  1 A. 
     In the second cellular telephone device B 2  according to the second embodiment, the CPU  45 B includes a decryption processing unit  261 , a decryption key request unit  262 , and an erasing unit  263 . 
     Based on information including a decryption key, the decryption processing unit  261  decrypts encryption information to generate the first identification/associated information. 
     In a case in which the infrared communication unit  20 B receives encryption information transmitted from the main cellular telephone device  1 A, the decryption key request unit  262  causes the radio communication unit  200 B to transmit request information (decryption key information transmission request information) to the main cellular telephone device  1 A to request transmission of decryption key information including a decryption key for decrypting the encryption information. 
     In a case in which the elapsed time measured by the timer  80 B exceeds a predetermined period of time, the erasing unit  263  erases the encryption information stored in the second encryption information storage unit  271 . 
     Next, a description is provided for operations of the communication system of the second embodiment, which includes the main cellular telephone device  1 A, the first cellular telephone device A 2 , and the second cellular telephone device B 2 . Examples 2-1, 2-2 and 2-3 are hereinafter described as examples relating to the communication system of the second embodiment. 
       FIG. 12  is a sequence diagram showing operations in Example 2-1 relating to the communication system of the second embodiment.  FIG. 13  is an example of the encryption information transmission completion notification mail in Examples 2-1 and 2-2.  FIG. 14  is a sequence diagram showing operations in Example 2-2 relating to the communication system of the second embodiment.  FIG. 15  is a sequence diagram showing operations in Example 2-3 relating to the communication system of the second embodiment.  FIG. 16  is an example of the encryption information transmission completion notification mail in Example 2-3. 
     Example 2-1 
     Operations in Example 2-1 are described with reference to  FIGS. 12 and 13 . 
     Since Steps ST 211  to ST 215  in Example 2-1 are similar to Steps ST 121  to ST 125  in Example 1-2, respectively, descriptions thereof are omitted. 
     It should be noted that, although not illustrated in the sequence diagram shown in  FIG. 12 , in a case in which the radio communication unit  200  receives a permission reply returned from the first cellular telephone device A 2  for permitting transmission of the first identification/associated information before the elapsed time measured by the timer  80  exceeds a predetermined period of time (for example, 5 minutes), the first communication permission unit  223  permits the infrared communication unit  20  to transmit the first identification/associated information to the second cellular telephone device B 2 . 
     Regarding Example 2-1, Steps ST 216  and after are described. 
     In Step ST 215 , in a case in which the elapsed time measured by the timer  80  exceeds a predetermined period of time (for example, 5 minutes), and thus the first communication permission unit  223  does not permit transmission of the first identification/associated information to the second cellular telephone device B 2 , in Step ST 216 , the encryption processing unit  224  encrypts the first identification/associated information to generate encryption information. In addition, the encryption processing unit  224  stores the encryption information thus generated in the encryption information storage unit  235  of the memory  44 . 
     In Step ST 217 , the second communication permission unit  225  permits the infrared communication unit  20  to transmit the encryption information, which is generated by the encryption processing unit  224  and is stored in the encryption information storage unit  235 , to the second cellular telephone device B 2 . As a result, the infrared communication unit  20  of the main cellular telephone device  1 A transmits the encryption information to the second cellular telephone device B 2 . 
     After transmitting encryption information to the second cellular telephone device B 2 , in Step ST 218 , the second notification unit  226  notifies the first cellular telephone device A 2  of the information that the encrypted first identification/associated information (encryption information) has been transmitted to the user Z, and information for requesting permission for transmitting a decryption key or the like for decrypting the encryption information to the user Z. 
     In the present example, as shown in  FIG. 13 , the second notification unit  226  transmits encryption information transmission completion notification mail stating that “Although there has been no reply from you (the user X), transmission of the encrypted information (a mail address) to the user Z has been completed. If you permit a decryption key for the encryption information to be transmitted to the user Z, please send your permission reply. Please note that, if the encryption information is not decrypted within 12 hours since the user Z received the encryption information, the encryption information will be erased.” 
     On the other hand, in the second cellular telephone device B 2 , in Step ST 219 , when the infrared communication unit  20 B receives the encryption information, the erasing unit  263  causes the timer  80 B as a second communication terminal side timing unit to start measuring the time. As a result, the timer  80 B measures (times) a period of time (elapsed time) since the infrared communication unit  20 B received the encryption information. 
     Subsequently, in the first cellular telephone device A 2  that has received the encryption information transmission completion notification mail, according to an operation of the user X, the first cellular telephone device A 2  transmits a reply to the main cellular telephone device  1 A for permitting transmission of the decryption key information in Step ST 220 . In the present example, the first cellular telephone device A 2  transmits the permission reply mail to the main cellular telephone device  1 A. 
     When the main cellular telephone device  1 A receives the permission reply mail, in Step ST 221 , the third communication permission unit  227  permits the radio communication unit  200  to transmit decryption key information. As a result, the radio communication unit  200  of the main cellular telephone device  1 A transmits the decryption key information to the second cellular telephone device B 2 . 
     In a case in which the second cellular telephone device B 2  receives the decryption key information before the elapsed time measured by the timer  80 B reaches a predetermined period of time (for example, 12 hours), in Step ST 222 , the decryption processing unit  261  of the second cellular telephone device B 2  decrypts the encryption information based on the decryption key information to generate the first identification/associated information. As a result, the first identification/associated information is obtained in the second cellular telephone device B 2  (the user Z). 
     In this way, in Example 2-1, the first identification/associated information (a mail address of the user X) is transmitted in an encrypted state (as encryption information) to the user Z (the second cellular telephone device B 2 ), in a state where permission of the user X is not obtained yet, and subsequently, when permission of the user X is obtained, decryption key information for decrypting the encryption information can be transmitted to the user Z (the second cellular telephone device B 2 ). 
     It should be noted that, as in the case of the second embodiment in which the decryption key information includes the usable number-of-times restriction information for restricting the number of times the decryption key can be utilized for decryption processing of the encryption information, for example, each time decryption is performed, “1” can be decremented from the usable number-of-times restriction information in the decryption key information. 
     As a result, when decryption is repeated, the usable number of times will be “0”, and thus the usable number of times of a decryption key can be restricted, which is preferable in terms of security. The restriction of the usable number of times of a decryption key can be realized, for example, through a technique similar to a copy guard technique (copy number-of-times restriction). As a result, decryption of encryption information can be restricted from being performed for an unlimited number of times. 
     Example 2-2 
     Example 2-2 is an example of a case in which the second cellular telephone device B 2  receives encryption information, but the second cellular telephone device B 2  does not subsequently receive decryption key information within a predetermined period of time. Since Steps ST 211  to ST 219  in Example 2-2 are similar to Steps ST 211  to ST 219  in Example 2-1, respectively, descriptions thereof are omitted. 
     Regarding Example 2-3, Steps ST 223  and after are described. 
     As shown in  FIG. 14 , in the second cellular telephone device B 2 , when a predetermined period of time (for example, 12 hours) has elapsed since the timer  80 B started timing, the timing by the timer  80 B is terminated in Step ST 223 . 
     Subsequently, in Step ST 224 , the erasing unit  263  erases the encryption information stored in the second encryption information storage unit  271  of the memory  44 B. 
     In this way, in Example 2-2, in a case in which decryption key information is not received within a predetermined period of time after the second cellular telephone device B 2  receives encryption information, the decryption key information is erased. Therefore, encryption information received by the second cellular telephone device B 2  will not remain in the second cellular telephone device B 2  indefinitely, which is preferable in terms of security of the first identification/associated information. 
     Example 2-3 
     Example 2-3 is an example of a case in which transmission of decryption key information to the second cellular telephone device B 2  is performed not by the main cellular telephone device  1 A, but by the first cellular telephone device A 2 . Since Steps ST 231  to ST 237  in Example 2-3 are similar to Steps ST 211  to ST 217  in Example 2-1, respectively, descriptions thereof are omitted. 
     Regarding Example 2-1, Steps ST 238  and after are described. 
     As shown in  FIG. 15 , after transmitting encryption information to the second cellular telephone device B 2 , in Step ST 238 , the second notification unit  226  of the main cellular telephone device  1 A notifies the first cellular telephone device A 2  of information of the fact that the encrypted first identification/associated information (encryption information) has been transmitted to the second cellular telephone device B 2  (the user Z), and information for requesting transmission of a decryption key or the like for decrypting the encryption information to the user Z. 
     In the present example, as shown in  FIG. 16 , the second notification unit  226  transmits encryption information transmission completion notification mail stating that “Although there has been no reply from you (the user X), transmission of the encrypted information (a mail address) to the user Z has been completed. In addition, a decryption key has been transmitted to you (the user X). When there is a request for the decryption key from the user Z, if you do not object, please transmit the decryption key to the user Z.” 
     After the encryption information transmission completion notification mail is transmitted, the third communication permission unit  227  permits the radio communication unit  200  to transmit the decryption key information stored in the decryption key information storage unit  237  to the first cellular telephone device A 1 . As a result, in Step ST 239 , the radio communication unit  200  of the main cellular telephone device  1 A transmits the decryption key information to the first cellular telephone device A 2 . 
     In the second cellular telephone device B 2 , in a case in which the infrared communication unit  20 B receives encryption information transmitted from the main cellular telephone device  1 A, in Step ST 240 , the decryption key request unit  262  requests the radio communication unit  200 B of the second cellular telephone device B 2  to transmit decryption key request information (information that includes a decryption key for decrypting the encryption information) stored in the decryption key request information storage unit  272 . In the present example, mail (decryption key information request mail) for requesting transmission of decryption key information is transmitted to the first cellular telephone device A 2  (the user X). 
     In the first cellular telephone device A 2  (the user X), in a case in which encryption information transmission completion notification mail or decryption key information request mail is received, and the user X determines that the decryption key information may be transmitted to the second cellular telephone device B 2  (the user Z), according to an operation of the user X, the first communication terminal side third communication permission unit  241  permits the radio communication unit  200 A of the first cellular telephone device A 2  to transmit the decryption key information stored in the decryption key information storage unit  251  to the second cellular telephone device B 2 . As a result, in Step ST 241 , the radio communication unit  200 A of the first cellular telephone device A 2  transmits the decryption key information to the second cellular telephone device B 2 . 
     Moreover, in Step ST 242 , the first communication terminal side notification unit  242  causes the radio communication unit  200 A to notify the main cellular telephone device  1 A of the fact that the decryption key information has been transmitted to the second cellular telephone device B 2 . In the present example, mail (decryption key information transmission completion notification mail) for notifying of the fact that the decryption key information has been transmitted to the second cellular telephone device B 2  is transmitted from the radio communication unit  200 A to the main cellular telephone device  1 A. 
     When the second cellular telephone device B 2  receives the decryption key information, the decryption processing unit  261  of the second cellular telephone device B 2  decrypts the encryption information based on the decryption key information to generate the first identification/associated information in Step ST 243 . As a result, the first identification/associated information is obtained in the second cellular telephone device B 2  (the user Z). 
     In this way, in Example 2-3, after transmitting encryption information to the second cellular telephone device B 2  (the user Z), transaction of decryption key information can be performed as a transaction between the first cellular telephone device A 2  (the user X) and the second cellular telephone device B 2  (the user Z) without involving the main cellular telephone device  1 A (the user Y). Therefore, the load on the main cellular telephone device  1 A (the user Y) is reduced. 
     Next, the communication system S of a third embodiment is described. The communication system S of the third embodiment includes a main cellular telephone device  1 B, a first cellular telephone device A 3 , and a second cellular telephone device B 3 . 
       FIG. 17  is a functional block diagram illustrating the functional configuration of the main cellular telephone device  1 B according to the third embodiment.  FIG. 18  is a functional block diagram illustrating the functional configuration of the first cellular telephone device A 3  according to the third embodiment.  FIG. 19  is a sequence diagram showing operations in Example 3 relating to the communication system of the third embodiment.  FIG. 20  is an example of data transmission completion notification mail in Example 3. 
     The functional configuration relating the memory  44  and the functional configuration relating the CPU  45  in the main cellular telephone device  1 B are mainly described with reference to  FIG. 17 . Since configurations that are not described in particular are similar to the configurations of the main cellular telephone device  1  in the first embodiment shown in  FIG. 4 , descriptions thereof are omitted. 
     In the main cellular telephone device  1 B according to the third embodiment, the memory  44  includes: a first identification/associated information storage unit  331 , a first selected information storage unit  332 , a reply request information storage unit  333 , and a second identification/associated information storage unit  334 . 
     The first identification/associated information storage unit  331 , the first selected information storage unit  332 , the reply request information storage unit  333 , and the second identification/associated information storage unit  334  in the third embodiment are similar to the first identification/associated information storage unit  131 , the first selected information storage unit  132 , the reply request information storage unit  133 , and the second identification/associated information storage unit  134  in the first embodiment, respectively; therefore, descriptions thereof are omitted. 
     In the main cellular telephone device  1 B according to the third embodiment, the CPU  45  includes a selection unit  321 , a reply request unit  322 , a first communication permission unit  323 , a fourth communication permission unit  324 , and a third notification unit  325 . 
     The selection unit  321 , the reply request unit  322  and the first communication permission unit  323  in the third embodiment are similar to the selection unit  121 , the reply request unit  122  and the first communication permission unit  123  in the first embodiment, respectively; therefore, descriptions thereof are omitted. 
     In a case in which a period of time measured by the timer  80  exceeds a predetermined period of time, the fourth communication permission unit  324  permits the infrared communication unit  20  to transmit the first identification/associated information to the second cellular telephone device B 3 . Moreover, the fourth communication permission unit  324  permits the radio communication unit  200  to transmit the second identification/associated information to the first cellular telephone device A 3 . 
     In a case in which the main cellular telephone device  1 B transmits the first identification/associated information to the second cellular telephone device B 3 , the third notification unit  325  causes the radio communication unit  200  to transmit, to the first cellular telephone device A 3 , information for notifying of the fact that the first identification/associated information has been transmitted to the second cellular telephone device B 3 . 
     Next, the functional configuration relating to the memory  44 A and the functional configuration relating the CPU  45 A in the first cellular telephone device A 3  according to the third embodiment are mainly described with reference to  FIG. 18 . Since configurations that are not described in particular are similar to the configurations of the first cellular telephone device A 1  in the second embodiment, descriptions thereof are omitted. 
     In the first cellular telephone device A 3  according to the third embodiment, the memory  44 A includes a third information storage unit  351  and an extracted information storage unit  352 . 
     The third information storage unit  351  stores third information. The third information includes: a plurality of pieces of third identification information corresponding to a plurality of communication terminals, respectively; and a plurality of pieces of third associated information that are associated with the plurality of pieces of third identification information, respectively. 
     The extracted information storage unit  352  stores predetermined third information (common third information) extracted by an extracting unit  342  of the CPU  45 , which will be described later. 
     In the first cellular telephone device A 3  according to the third embodiment, the CPU  45 A includes a comparing unit  341 , an extracting unit  342 , and a display control unit  343 . 
     In a case in which the radio communication unit  200 A receives the second identification/associated information, the comparing unit  341  compares the second identification/associated information with each of the plurality of pieces of third information stored in the third information storage unit  351 . 
     From among the plurality of pieces of third information stored in the third information storage unit  351 , the extracting unit  342  extracts predetermined third information (the common third information) that includes contents common with the second identification/associated information based on a result of the comparison by the comparing unit  341 . 
     The display control unit  343  causes the display unit  21  to display the predetermined third information (the common third information) that is extracted by the extracting unit  342  and is stored in the extracted information storage unit  352 . For example, the display control unit  343  causes the display unit  21  to display the name of the user Z. 
     Next, a description is provided for operations of the communication system of the third embodiment, which includes the main cellular telephone device  1 B, the first cellular telephone device A 3 , and the second cellular telephone device B 3 . Example 3 is hereinafter described as examples relating to the communication system of the third embodiment. 
       FIG. 19  is a sequence diagram showing operations in Example 3 relating to the communication system of the third embodiment.  FIG. 20  is an example of first identification/associated information transmission completion notification mail and second identification/associated information notification mail in Example 3. 
     Example 3 
     Operations in Example 3 are described with reference to  FIGS. 19 and 20 . 
     Since Steps ST 311  to ST 314  in Example 3 are similar to Steps ST 121  to ST 124  in Example 1-2, respectively, descriptions thereof are omitted. 
     Regarding Example 3, Steps ST 315  and after are described. 
     It should be noted that, although not illustrated in  FIG. 19 , in a case in which the radio communication unit  200  receives a permission reply returned from the first cellular telephone device A 3  for permitting transmission of the first identification/associated information before the elapsed time measured by the timer  80  exceeds a predetermined period of time, the first communication permission unit  323  of the main cellular telephone device  1 B permits the infrared communication unit  20  to transmit the first identification/associated information selected by the selection unit  321 . 
     In Step ST 315 , in a case in which a period of time measured by the timer  80  exceeds a predetermined period of time (for example, 5 minutes), the fourth communication permission unit  324  permits the infrared communication unit  20  to transmit the first identification/associated information to the second cellular telephone device B 3 . As a result, the first identification/associated information is transmitted to the second cellular telephone device B 3 . 
     In Step ST 316 , the fourth communication permission unit  324  permits the radio communication unit  200  to transmit the second identification/associated information to the first cellular telephone device A 3 . 
     Moreover, in Step ST 317 , the third notification unit  325  transmits, to the radio communication unit  200 , mail for notifying of the fact that transmission of the first identification/associated information to the second cellular telephone device B 3  has been completed. In the present example, as shown in  FIG. 20 , the third notification unit  325  transmits data transmission completion notification mail stating that “Although there has been no reply from you (the user X), transmission of your (the user X&#39;s) mail address to the user Z has been completed. In return, you are provided with the profile information of the user Z”. 
     In addition, for the first cellular telephone device A 3 , in Step ST 318 , in a case in which the radio communication unit  200  receives the second identification/associated information, the comparing unit  341  compares the second identification/associated information with each of the plurality of pieces of third information stored in the third information storage unit  351 . 
     In Step ST 319 , from among the plurality of pieces of third information stored in the third information storage unit  351 , the extracting unit  342  extracts predetermined third information (the common third information) that includes contents common with the second identification/associated information based on a result of the comparison by the comparing unit  341 . For example, in a case in which the name of the user Z is commonly included in the second identification/associated information and the third information, the extracting unit  342  extracts the name of the user Z. 
     In Step ST 320 , the display control unit  343  causes the display unit  21  to display the predetermined third information (the common third information) that is extracted by the extracting unit  342  and is stored in the extracted information storage unit  352 . 
     As described above, according to the third embodiment, transmission of the first identification/associated information to the second cellular telephone device B 3 , and transmission of the second identification/associated information to the first cellular telephone device A 3  are both performed. Therefore, from the viewpoint of the user X, although the user X&#39;s own information (the first identification/associated information) is known to the user Z, the user X can also know information of the other party (the user Z) (the second identification/associated information) who knows the user X&#39;s own information; therefore, a state in which the destination of personal information is unknown to oneself can be prevented from continuing. 
     Moreover, since the name of the user Z can be extracted to be displayed on the display unit  21 , for example, the user X can easily and visually identify the other party (the user Z) who knows the user X&#39;s own information. 
     In the third embodiment, as described above, in a case in which a period of time measured by the timer  80  exceeds a predetermined period of time, the fourth communication permission unit  324  of the main cellular telephone device  1 B permits the infrared communication unit  20  to transmit the first identification/associated information to the second cellular telephone device B 3 , and permits the radio communication unit  200  to transmit the second identification/associated information to the first cellular telephone device A 3 ; however, it is not limited thereto. 
     For example, in place of the fourth communication permission unit  324 , the main cellular telephone device  1 B can include “a fifth communication permission unit (not illustrated) that permits the radio communication unit  200  to transmit the second identification/associated information to the first cellular telephone device A 3  in a case in which a period of time measured by the timer  80  exceeds a predetermined period of time”. In an embodiment in which the main cellular telephone device  1 B includes the fifth communication permission unit as described above, the first cellular telephone device A 3  can receive the second identification/associated information, and thus the user X can determine whether the first identification/associated information may be transmitted based on the second identification/associated information thus received. 
     Furthermore, the first identification/associated information may include transmission number-of-times information on the number of times of transmission, and restricted number-of-times information including information on the restricted number of times of transmission. In addition, in a case in which the first identification/associated information includes the transmission number-of-times information and the restricted number-of-times information, the first communication unit and/or the second communication unit may be configured so as not to transmit the first identification/associated information in a case in which the transmission number of times included in the transmission number-of-times information is no more than the restricted number of times of transmission included in the restricted number-of-times information. 
       FIG. 21  is a flowchart showing operations in a case in which the first identification/associated information includes the transmission number-of-times information and the restricted number-of-times information. Restriction of the transmission number of times can be realized, for example, through a technique similar to a copy guard technique (copy number-of-times restriction). 
     As shown in  FIG. 21 , in Step ST 401 , the user Z operates the main cellular telephone device  1  to access the address book of the main cellular telephone device  1  to obtain a mail address of the user X. 
     In Step ST 402 , the transmission (transmittable) number of times in the transmission number-of-times information included in the mail address is compared with the restricted number of times in the restricted number-of-times information. Here, the restricted number of times is “zero”. In a case in which the transmittable number of times is at least one (for example, three) (YES), the processing advances to Step ST 403 . Moreover, in a case in which the transmittable number of times is zero (NO), the processing is terminated (transmission is not permitted). 
     In a case in which the transmittable number of times is at least one (YES), in Step ST 403 , the main cellular telephone device  1  can transmit a mail address of the user X to the second cellular telephone device B. 
     When the mail address of the user X is transmitted, “one” is decremented from the transmittable number of times in the transmission number-of-times information included in this mail address. For example, the transmittable number of times may become two. As a result, transmission (transfer) of a mail address of the user X from the main cellular telephone device  1  can be restricted from being performed for an unlimited number of times. 
     Next, the communication system S of a fourth embodiment is described. 
     First, with reference to  FIG. 22 , a description is provided for the communication system S that includes a main cellular telephone device  1 D as the main communication terminal, a first cellular telephone device A 4  as the first communication terminal, a second cellular telephone device B 4  as the second communication terminal, and a server W. 
       FIG. 22  is a diagram illustrating an overview of the communication system S including the main cellular telephone device  1 D. 
     As shown in  FIG. 22 , the communication system S includes the main cellular telephone device  1 D, the first cellular telephone device A 4 , the second cellular telephone device B 4 , and the server W. Here, the users of the first cellular telephone device A 4 , the main cellular telephone device  1 D, and the second cellular telephone device B 4  are referred to as the user X, the user Y and the user Z, respectively. 
     The main cellular telephone device  1 D can transmit and receive predetermined information to and from the first cellular telephone device A 4 , the second cellular telephone device B 4  and the server W by way of wireless communication (the second communication method) via the communication network N. Moreover, the main cellular telephone device  1 D can transmit and receive predetermined information to and from the second cellular telephone device B 4  by way of infrared communication (the first communication method). 
     In a case in which the main cellular telephone device  1 D transmits predetermined information to the second cellular telephone device B 4  by way of infrared communication, the main cellular telephone device  1 D is disposed adjacently to the second cellular telephone device B 4 . On the other hand, the first cellular telephone device A 4  is disposed at a position separated from the main cellular telephone device  1 D and the second cellular telephone device B 4 . In other words, the main cellular telephone device  1 D is disposed at a position at which it is not possible to directly confirm whether personal information of the user X may be transmitted to the user (the user X) of the first cellular telephone device A 4 . Even in this state, the communication system S in the present embodiment achieves an effect. 
     The server W can receive a variety of information transmitted from the main cellular telephone device  1 D, the first cellular telephone device A 4  and the second cellular telephone device B 4 . Moreover, the server W can transmit a variety of information to the main cellular telephone device  1 D, the first cellular telephone device A 4  and the second cellular telephone device B 4 . 
     Next, a detailed description is provided for a configuration of the main cellular telephone device  1 D according to the communication system S of the present embodiment with reference to  FIG. 23 .  FIG. 23  is a perspective view showing an appearance of the main cellular telephone device  1 D in the opened state. 
     As shown in  FIG. 23 , the main cellular telephone device  1 D includes the operation unit side body  2  and the display unit side body  3  as its bodies. The operation unit side body  2  and the display unit side body  3  are connected so as to be openable and closable via a connecting portion  4  including a hinge mechanism. More specifically, an upper end portion of the operation unit side body  2  and a lower end portion of the display unit side body  3  are connected via the connecting portion  4  including the hinge mechanism. As a result, the main cellular telephone device  1 D is configured such that the operation unit side body  2  and the display unit side body  3  connected via the hinge mechanism can be relatively moved. In other words, the main cellular telephone device  1 D can be transformed between a state in which the operation unit side body  2  and the display unit side body  3  are opened (the opened state), and a state in which the operation unit side body  2  and the display unit side body  3  are folded (the closed state). Here, the closed state refers to a state in which both bodies are disposed so as to be mutually superimposed. The opened state refers to a state in which both bodies are disposed so as not to be mutually superimposed. 
     An outer face of the operation unit side body  2  is configured with a front case  2   a  and a rear case  2   b . The operation unit side housing  2  is configured to expose, on the front case  2   a  side, both an operation key set  11  as an input unit and a microphone  12  to which sound produced by the user of the main cellular telephone device  1 D during a phone call is input. 
     The operation key set  11  is configured with: function setting operation keys  13  for operating various functions such as for various settings, a telephone number directory function and a mail function; input operation keys  14  for inputting digits of a telephone number, characters for mail, etc.; and a selection operation key  15  for performing selection of the various operations and scrolls up, down, left and right. Predetermined functions are assigned (key assignment) to each key configuring the operation key set  11  in accordance with the opened/closed state of the operation unit side body  2  and the display unit side body  3 , various modes, and the type of application that is running. An operation corresponding to a function assigned to each key is executed by the user depressing each key. 
     The microphone  12  is disposed on an outer end side that is opposite to the connecting portion  4  side in a longitudinal direction of the operation unit side body  2 . In other words, the microphone  12  is disposed on one outer end side of the main cellular telephone device  1 D in the opened state. 
     An interface (not illustrated) for communicating with an external device (for example, a host device) is disposed on one side face of the operation unit side body  2 . Side keys to which predetermined functions are assigned and an interface (not illustrated) where external memory is inserted and removed are disposed on another side face of the operation unit side body  2 . The interfaces are covered by caps. When not in use, an interface is covered by the respective cap. 
     An outer surface of the display unit side body  3  is configured with a front case  3   a  and a rear case  3   b . On the front case  3   a  of the display unit side body  3 , a display unit  21  for displaying a variety of information, and a speaker  22  as a receiver that outputs sound of the other party of a phone call are disposed so as to be externally exposed. Here, the display unit  21  is configured with a liquid crystal display panel, a drive circuit that drives the liquid crystal display panel, and a light source unit such as a backlight that irradiates light from the back face side of the liquid crystal display panel. 
     Next, a circuit configuration of the main cellular telephone device  1 D is described with reference to  FIG. 24 .  FIG. 24  is a circuit block diagram illustrating a circuit configuration of the main cellular telephone device  1 D according to the fourth embodiment. 
     As shown in  FIG. 24 , the operation unit side body  2  of the main cellular telephone device  1 D includes: the radio communication unit  200  as the second communication unit; the operation unit  101  as the input unit; the microphone  12 ; the LCD control unit  42 ; the sound processing unit  43 ; the memory  44 ; the CPU  45 ; the power supply unit  46 ; the control IC  47 ; and the timer  80  as the timing unit. Moreover, the display unit side body  3  of the main cellular telephone device  1 D includes: the display unit  21 , the speaker  22 , the driver IC  25 , and the infrared communication unit  20  as the first communication unit. It should be noted that a communication unit conforming to, for example, Bluetooth (IEEE 802.15.1, registered trademark) may be provided in place of the infrared communication unit  20 , or in addition to the infrared communication unit  20 . 
     The radio communication unit  200  includes an antenna unit  90  and a communication processing unit  201 . 
     The radio communication unit  200  is configured so as to be capable of externally transmitting and receiving predetermined information. The radio communication unit  200  performs communication by way of a method using radio waves (the second communication method) that is different from infrared communication. The radio communication unit  200  can transmit predetermined information to the first cellular telephone device A 4  via the predetermined communication network N (see  FIG. 22 ). The radio communication unit  200  can, for example, transmit predetermined information as a text of E-mail or as an attachment to E-mail. 
     The radio communication unit  200  can, for example, transmit information such as: address information (first identification information) such as a mail address and a telephone number; profile information (first associated information) such as a name, an address and a profile; information for prompting a user (the user Z) of another cellular telephone device to transmit a reply of permitting transmission of predetermined information; information for permitting transmission of predetermined information; and decryption key information including a decryption key for decrypting predetermined encryption information. 
     Based on a predetermined communication method (for example, CDMA (Code Division Multiple Access) 2000 — 1x or the like), the antenna unit  90  performs communication by phone or mail with other communication terminals via a base station. 
     The communication processing unit  201  is configured with a transmitting circuit that performs transmission processing and a receiving circuit that performs reception processing. The communication processing unit  201  performs demodulation processing by the receiving circuit on a signal received via the antenna unit  90 , and transmits the signal thus processed to the CPU  45 . In addition, the communication processing unit  201  performs modulation processing by the transmitting circuit on the signal transmitted from the CPU  45 , and transmits the signal to a base station via the antenna unit  90 . 
     The operation unit  101  is configured to include the operation key set  11 . 
     The LCD control unit  42  performs predetermined image processing on input image data in accordance with control by the CPU  45 , and outputs the image data, on which the image processing has been performed, to the driver IC  25 . The driver IC  25  stores the image data being input from the LCD control unit  42  in frame memory, and outputs the image data stored in the frame memory to the display unit  21  at a predetermined timing. 
     The display unit  21  displays predetermined characters and images based on the data that is input from the driver IC  25 . 
     The memory  44  stores predetermined data. More specifically, the memory  44  has various storage units that store a variety of data and application programs for operating various functions (see  FIG. 25 ). Details of the memory  44  will be described later. 
     The CPU  45  controls the entirety of the main cellular telephone device  1 D. The CPU  45  performs predetermined control of, in particular, the radio communication unit  200 , the LCD control unit  42  and the sound processing unit  43 . Details of the CPU  45  will be described later. 
     In accordance with control by the CPU  45 , the sound processing unit  43  performs predetermined sound processing on a signal transmitted from the communication processing unit  201 , and outputs the signal on which the sound processing has been performed to the speaker  22 . The speaker  22  externally outputs sound based on a signal that is transmitted from the sound processing unit  43 . Moreover, in accordance with control by the CPU  45 , the sound processing unit  43  performs predetermined processing on a signal that is input from the microphone  12 , and outputs the signal thus processed to the communication processing unit  201 . The communication processing unit  201  performs predetermined processing on the signal that is input from the sound processing unit  43 , and outputs the signal thus processed to the antenna unit  90 . 
     The power supply unit  46  is configured to include a battery (not illustrated). The battery is composed of a lithium-ion battery having predetermined capacity. 
     The control IC  47  converts a power supply voltage, which is supplied from the power supply unit  46 , into a predetermined power supply voltage, and supplies the power supply voltage thus converted to each unit (for example, the CPU  45  and the like) of the main cellular telephone device  1 D. 
     The timer  80  has a timing function. The timer  80  is configured to measure a period of time elapsed from a predetermined time, and to be capable of outputting a predetermined signal (a time-up signal) to the CPU  45  when the elapsed period of time exceeds a predetermined period of time. For example, the timer  80  measures a period of time since the radio communication unit  200  transmitted information for requesting a reply (reply request information). 
     The infrared communication unit  20  is disposed in the vicinity of the end portion that is opposite to the connecting portion  4  in the display unit side body  3 . The infrared communication unit  20  is configured to be compatible with the IrDA (Infrared Data Association) standard. The infrared communication unit  20  is configured to be capable of externally outputting a predetermined signal. The infrared communication unit  20  is configured to be capable of outputting information stored in the memory  44  and the like, which will be described later. 
     The infrared communication unit  20  transmits predetermined information stored in the memory  44  to the second cellular telephone device B 4  that is disposed outside and includes a similar infrared communication unit  20 B. The infrared communication unit  20  can transmit and receive information by way of an infrared communication method (the first communication method) using an infrared ray, which is a communication method different from that of the radio communication unit  200 . Information transmitted from the communication unit  20  of the main cellular telephone device  1 D is received by the communication unit  20 B in the second cellular telephone device B as the second communication terminal. 
     The infrared communication unit  20  can transmit encryption information that is address information, profile information or the like of the user Y of the main cellular telephone device  1 D, on which encryption processing has been performed, and address information, profile information or the like of the user X of the first cellular telephone device A 4 . Moreover, the infrared communication unit  20  can also transmit and receive encryption information that is profile information or the like on which encryption processing has been performed. 
     In the infrared communication mode that enables infrared communication, the selection operation key  15  is assigned with a function of selecting information (for example, address information and profile information) to be transmitted to another cellular telephone device (for example, the second cellular telephone device B 4 ) as the second communication terminal, and a function of determining transmission of the information thus selected. 
     Next, functions of the main cellular telephone device  1 D according to the fourth embodiment are described in detail with reference to  FIG. 25 .  FIG. 25  is a functional block diagram illustrating a functional configuration of the main cellular telephone device  1 D according to the fourth embodiment. Here, the functional configuration relating to the memory  44  and the functional configuration relating to the CPU  45  are mainly described with reference to  FIG. 25 . 
     The memory  44  includes a first identification/associated information storage unit  431  as a first storage unit, a first selected information storage unit  432 , a reply request information storage unit  433 , a second identification/associated information storage unit  434  as a second storage unit, an encryption information storage unit  435 , a third information storage unit  436  as a third storage unit, and a decryption key information storage unit  437 . 
     The first identification/associated information storage unit  431  stores the first identification information corresponding to the first cellular telephone device A 4 , and the first associated information that is associated with the first identification information. The first identification information is information corresponding to the first cellular telephone device A 4  or its user (the user X), and is, for example, a mail address, a telephone number (address information) and the like of the user X. The first associated information is information associated with the first identification information, and is, for example, a name, an address, a profile (profile information), a facial photograph and the like of the user X. 
     The first selected information storage unit  432  stores information selected by a selection unit  421  of the CPU  45 , which will be described later. More specifically, the first selected information storage unit  432  stores “a part or all of the first identification information and the first associated information stored in the first identification/associated information storage unit  431 ” selected by the selection unit  421  of the CPU  45 . 
     It should be noted that the “part or all of the first identification information and the first associated information” is hereinafter also referred to as “first identification/associated information”. 
     The reply request information storage unit  433  stores reply request information transmitted by a reply request unit  422  of the CPU  45 , which will be described later. 
     The second identification/associated information storage unit  434  stores second identification information corresponding to the second cellular telephone device B 4 , and second associated information that is associated with the second identification information. The second identification information is information corresponding to the second cellular telephone device B 4  or its user (the user Z), and is, for example, a mail address, a telephone number (address information) and the like of the user Z. The second associated information is information associated with the second identification information, and is, for example, a name, an address, a profile (profile information), a photograph and the like of the user Z. 
     It should be noted that the “part or all of the second identification information and the second associated information” is hereinafter also referred to as “second identification/associated information”. 
     The encryption information storage unit  435  stores encryption information generated by an encryption processing unit  424  that will be described later. 
     The third information storage unit  436  stores server address information corresponding to the server W. 
     The decryption key information storage unit  437  stores decryption key information. The decryption key information includes a decryption key for decrypting predetermined encryption information, etc. 
     Next, the functional configuration of the CPU  45  is described. The CPU  45  includes a selection unit  421 , a reply request unit  422 , a first transmission permission unit  423 , an encryption processing unit  424 , an encryption information transmission permission unit  425 , and a first notification information transmission unit  426 . 
     It should be noted that the CPU  45  of the main cellular telephone device  1 D performs control such that the radio communication unit  200  is preferentially used rather than the infrared communication unit  20 , for communication with the first cellular telephone device A 4 . By performing control in this way, even in a case in which the user (the user X) of the first cellular telephone device A 4  is not present near the user (the user Y) of the main cellular telephone device  1 D, communication with the first cellular telephone device A 4  can be performed more reliably by using the radio communication unit  200  via the communication network N. 
     From among the first identification/associated information stored in the first identification/associated information storage unit  431 , the selection unit  421  selects information to be transmitted by the infrared communication unit  20  to the second cellular telephone device B 4 . For example, the selection unit  421  selects a mail address of the user X. The first identification/associated information selected by the selection unit  421  is also referred to as “first selected information”. The selection unit  421  causes the first selected information storage unit  432  of the memory  44  to store the first selected information. 
     In a case in which the information selected by the selection unit  421  is the first identification/associated information, the reply request unit  422  causes the radio communication unit  200  to transmit, to the first cellular telephone device A 4 , reply request information for requesting a reply regarding whether to permit transmission of the first identification/associated information (the first selected information). For example, in a case in which the first selected information is a mail address of the user X, the radio communication unit  200  is caused to transmit, to the first cellular telephone device A 4 , reply request mail for requesting a reply regarding whether to permit transmission of the mail address of the user X. 
     In a case in which a period of time measured by the timer  80  exceeds a predetermined period of time (for example, 5 minutes), the first transmission permission unit  423  does not permit the infrared communication unit  20  to transmit the first identification/associated information (the first selected information) to the second cellular telephone device B 4 . 
     Moreover, in a case in which the radio communication unit  200  receives a permission reply before the period of time measured by the timer  80  exceeds the predetermined period of time, the first transmission permission unit  423  permits the infrared communication unit  20  to transmit the first identification/associated information to the second cellular telephone device B 4 . The permission reply is a reply returned from the first cellular telephone device A 4  for permitting transmission of the first identification/associated information. For example, in a case in which the radio communication unit  200  receives a permission reply for permitting transmission of the mail address of the user X, the first transmission permission unit  423  permits the infrared communication unit  20  to transmit the mail address of the user X to the second cellular telephone device B 4 . 
     In a case in which the first transmission permission unit  423  does not permit the infrared communication unit  20  to transmit the first identification/associated information to the second cellular telephone device B 4 , the encryption processing unit  424  performs encryption processing on the first identification/associated information. In addition, the encryption processing unit  424  causes the decryption key information storage unit  437  of the memory  44  to store decryption key information including a decryption key for decrypting this encryption information. 
     The encryption information transmission permission unit  425  permits the infrared communication unit  20  to transmit the encryption information stored in the encryption information storage unit  435  and the server address information stored in the third information storage unit  436  to the second cellular telephone device B 4 . 
     The encryption information transmission permission unit  425  permits the infrared communication unit  20  to transmit the encryption information generated by the encryption processing unit  424  to the second cellular telephone device B 4 . 
     The first notification information transmission unit  426  causes the radio communication unit  200  to transmit the first notification information to the server W identified by way of the server address information. The first notification information is information that includes: the notification information for notifying of the fact that the first identification/associated information has been transmitted to the second cellular telephone device B 4 ; the first identification information; and the second identification information. 
     Next, the functional configuration relating the memory  44 A and the functional configuration relating the CPU  45 A in the first cellular telephone device A 4  according to the present embodiment are mainly described with reference to  FIG. 26 .  FIG. 26  is a functional block diagram illustrating the functional configuration of the first cellular telephone device A 4  according to the fourth embodiment. Since configurations that are not described in particular are similar to the configurations of the main cellular telephone device  1 D, descriptions thereof are omitted. Moreover, among the configurations of the first cellular telephone device, the configurations similar to the configurations of the main cellular telephone device are denoted by reference numerals with a suffix “A” (for example, the infrared communication unit  20  of the main cellular telephone device is denoted as an infrared communication unit  20 A of the first cellular telephone device). 
     In the first cellular telephone device A 4 , the memory  44 A includes a first communication terminal side first storage unit  451 , a first communication terminal side second storage unit  452 , a first communication terminal side decryption key information storage unit  453 , and a non-permission information storage unit  454 . 
     The first communication terminal side first storage unit  451  stores the first identification information. 
     The first communication terminal side second storage unit  452  stores the second identification information and the server address information that are included in the second notification information received by the radio communication unit  200 . 
     The first communication terminal side decryption key information storage unit  453  stores the decryption key information that is transmitted from the main cellular telephone device  1 D and is received via the radio communication unit  200 A. 
     The non-permission information storage unit  454  stores non-permission information. 
     In the first cellular telephone device A 4 , the CPU  45 A includes a first communication terminal side decryption key information transmission unit  441 , a non-permission information transmission unit  442 , and a reply transmission unit  443 . 
     In a case in which the radio communication unit  200  receives the second notification information, the first communication terminal side decryption key information transmission unit  441  causes the radio communication unit  200  to transmit the decryption key information stored in the first communication terminal side decryption key information storage unit  453  to the server W that is identified by way of the server address information stored in the first communication terminal side second storage unit  452 . 
     The non-permission information transmission unit  442  causes the radio communication unit  200  to transmit the non-permission information to the server W. The non-permission information is information for not permitting transmission of the decryption key information stored in the first communication terminal side decryption key information storage unit  453  to the second cellular telephone device B 4 . 
     The reply transmission unit  443  causes the radio communication unit  200  to transmit various replies to the outside by way of an operation of the first cellular telephone device A 4  by the user X. 
     Next, the functional configuration relating to the memory  44 B and the functional configuration relating to the CPU  45 B in the second cellular telephone device B 4  are mainly described with reference to  FIG. 27 .  FIG. 27  is a functional block diagram illustrating the functional configuration of the second cellular telephone device B 4  according to the fourth embodiment. Since configurations that are not described in particular are similar to the configurations of the main cellular telephone device  1 D, descriptions thereof are omitted. Moreover, among the configurations of the second cellular telephone device, configurations similar to the configurations of the main cellular telephone device are denoted by reference numerals with a suffix “B” (for example, the infrared communication unit  20  of the main cellular telephone device is denoted as the infrared communication unit  20 B of the second cellular telephone device). 
     In the second cellular telephone device B 4 , the timer  80 B measures a period of time elapsed since the infrared communication unit  20 B received encryption information transmitted from the main communication terminal  1 . 
     In the second cellular telephone device B 4 , the memory  44 B includes a second communication terminal side encryption information storage unit  471 , a first request information storage unit  472 , and a second communication terminal side decryption key information storage unit  473 . 
     The second encryption information storage unit  471  stores encryption information, server address information and the like that are transmitted from the main cellular telephone device  1 D and is received via the infrared communication unit  20 B. 
     The first request information storage unit  472  stores first request information for requesting decryption key information. 
     The second communication terminal side decryption key information storage unit  473  stores decryption key information. 
     In the second cellular telephone device B 4 , the CPU  45 B includes a decryption processing unit  461 , a second communication terminal side decryption key information request unit  462 , and a second communication terminal side erasing unit  463 . 
     Based on a decryption key included in the decryption key information transmitted from the server W, the decryption processing unit  461  performs decryption processing on the encryption information stored in the second communication terminal side encryption information storage unit  471 , and generates the first identification/associated information. 
     The second communication terminal side decryption key information request unit  462  causes the radio communication unit  200 B to transmit the first request information for requesting decryption key information to the server W that is identified by way of the server address information stored in the second communication terminal side encryption information storage unit  471 . 
     In a case in which the radio communication unit  200 B receives first erasing instruction information, the second communication terminal side erasing unit  463  erases the encryption information stored in the second communication terminal side encryption information storage unit  471 . 
     Moreover, in a case in which a period of time measured by the timer  80 B has passed a predetermined period of time, the second communication terminal side erasing unit  463  erases the encryption information stored in the second communication terminal side encryption information storage unit  471 . 
     Next, the server W is described with reference to  FIG. 28 .  FIG. 28  is a functional block diagram illustrating the functional configuration of the server W according to the fourth embodiment. 
     The server W includes a server side communication unit  960  as a second server side communication unit, a timer  980 , memory  940 , and a CPU  910 . 
     The server side communication unit  960  includes a communication processing unit  961 . The server side communication unit  960  is configured so as to be capable of externally transmitting and receiving predetermined information. The server side communication unit  960  can transmit predetermined information to the main cellular telephone device  1 D, the first cellular telephone device A 4  and the second cellular telephone device B 4  via the predetermined communication network N (see  FIG. 22 ). The server side communication unit  960  can perform communication by way of a method using radio waves (the second communication method) that is different from infrared communication, or can perform wired communication as well. The server side communication unit  960  can, for example, transmit predetermined information as a text of E-mail or as an attachment to E-mail. 
     The communication processing unit  961  is configured with a transmitting circuit that performs transmission processing and a receiving circuit that performs reception processing. The communication processing unit  961  performs demodulation processing by the receiving circuit on a signal received via the antenna unit or wired communication, and transmits the signal thus processed to the CPU  910 . In addition, the communication processing unit  961  performs modulation processing by the transmitting circuit on the signal transmitted from the CPU  910 , and transmits the signal to a base station via the antenna unit or wired communication. 
     The timer  980  measures (times) a period of time since the non-permission information was received from the first cellular telephone device A 4 . 
     In the server W, the memory  940  includes a server side first storage unit  941 , a server side second storage unit  942 , a server side decryption key information storage unit  943 , a second request information storage unit  944 , a third notification information storage unit  945 , a fourth notification information storage unit  946 , a non-permission information storage unit  947 , and a first erasing instruction information storage unit  948 . 
     The server side second storage unit  942  stores server address information. 
     The server side first storage unit  941  stores the first identification information, the second identification information and the like that are included in the first notification information received by the server side communication unit  960 . 
     The server side decryption key information storage unit  943  stores decryption key information and the like transmitted from the first cellular telephone device A 4 . 
     The second request information storage unit  944  stores the second request information for requesting transmission of encryption information. 
     The third notification information storage unit  945  stores third notification information for notifying of the fact that decryption key information is stored in the server side decryption key information storage unit  943 . 
     The fourth notification information storage unit  946  stores fourth notification information for notifying of the fact that decryption key information is not stored in the server side decryption key information storage unit  943 . 
     The non-permission information storage unit  947  stores non-permission information transmitted from the first cellular telephone device A 4 . 
     The first erasing instruction information storage unit  948  stores the first erasing instruction information. 
     In the server W, the CPU  910  includes a second communication information transmission unit  911 , a server side decryption key information transmission unit  912 , a server side determination unit  913 , a server side decryption key information request unit  914 , a third notification information transmission unit  915 , a fourth notification information transmission unit  916 , a server side erasing unit  917 , and a first erasing instruction information transmission unit  918 . 
     In a case in which the server side communication unit  960  receives the first notification information, the second communication information transmission unit  911  causes the server side communication unit  960  to transmit the second notification information to the first cellular telephone device A 4  that is identified by way of the first identification information stored in the server side first storage unit  941 . The second notification information includes: notification information for notifying of the fact that the first identification/associated information has been encrypted and transmitted from the main cellular telephone device  1 D to the second cellular telephone device B 4 ; second identification information stored in the server side first storage unit  941 ; and server address information stored in the server side second storage unit  942 . 
     In a case in which the server side communication unit  960  receives the first request information, the server side decryption key information transmission unit  912  causes the server side communication unit  960  to transmit the decryption key information stored in the server side decryption key information storage unit  943  to the second cellular telephone device B 4  identified by way of the second stored identification information stored in the server side first storage unit  941 . 
     In a case in which the server side communication unit  960  receives the first request information, the server side determination unit  913  determines whether the decryption key information is stored in the server side decryption key information storage unit  943 . 
     In a case in which the server side determination unit  913  determines that the encryption information is not stored in the server side decryption key information storage unit  943 , the server side decryption key information request unit  914  causes the server side communication unit  960  to transmit, to the first cellular telephone device A 4 , the second request information for requesting transmission of the encryption information. 
     In a case in which the server side communication unit  960  receives decryption key information, the third notification information transmission unit  915  causes the server side communication unit  960  to transmit the third notification information for notifying of the fact that the decryption key information is stored in the server side decryption key information storage unit  943 , to the second cellular telephone device B 4  identified by way of the second identification information stored in the server side first storage unit  941 . 
     In a case in which the server side determination unit  913  determines that the decryption key information is not stored in the server side decryption key information storage unit  943 , the fourth notification information transmission unit  916  causes the server side communication unit  960  to transmit the fourth notification information for notifying of the fact that the decryption key information is not stored in the server side decryption key information storage unit  943 , to the second cellular telephone device B 4  identified by way of the second identification information stored in the server side first storage unit  941 . 
     In a case in which the server side communication unit  960  receives non-permission information, the server side erasing unit  917  erases the decryption key information stored in the server side decryption key information storage unit  943 . The decryption key information includes the decryption key itself, and in addition, a variety of information regarding the decryption key (history associated with the decryption key in the server W, etc.). In a case in which the server side communication unit  960  receives non-permission information, the server side erasing unit  917  starts timing by the timer  980 . 
     In a case in which the server side communication unit  960  receives the non-permission information, the first erasing instruction information transmission unit  918  causes the server side communication unit  960  to transmit the first erasing instruction information to the second cellular telephone device B 4 . The first erasing instruction information includes an instruction to erase the encryption information stored in the second communication terminal side encryption information storage unit  471 . 
     Next, with reference to  FIGS. 29 to 37 , descriptions are provided for operations of the communication system of the present embodiment, which includes the main cellular telephone device  1 D, the first cellular telephone device A 4 , the second cellular telephone device B 4 , and the server W. Examples 4-1 to 5 are hereinafter described as examples according to the communication system of the present embodiment. 
       FIG. 29  is a sequence diagram showing operations in Example 4-1 relating to the communication system S of the fourth embodiment.  FIG. 30  is an example of the reply request mail in Example 4-1.  FIG. 31  is an example of the second notification information mail in Example 4-1.  FIG. 32  is a sequence diagram showing operations in Example 4-2 relating to the communication system S of the fourth embodiment.  FIG. 33  is an example of the second request information mail in Example 4-2.  FIG. 34  is an example of the third notification information mail in Example 4-2.  FIG. 35  is a sequence diagram showing operations in Example 4-3 relating to the communication system S of the fourth embodiment.  FIG. 36  is a sequence diagram showing operations in Example 4-4 relating to the communication system S of the fourth embodiment.  FIG. 37  is a sequence diagram showing operations in Example 4-5 according to the communication system S of the fourth embodiment. 
     Example 4-1 
     Operations in Example 4-1 are described with reference to  FIGS. 29 to 31 . Example 4-1 is an example in a case in which there is a request for decryption key information from the user Z to the server W, in a state in which encryption information is transmitted to the user Z, and decryption key information is registered (stored) in the server W. 
     When the user Y performs an operation to select information to be transmitted to the user Z from among the first identification/associated information, in Step ST 511 , the selection unit  421  of the CPU  45  selects information (the first selected information) to be transmitted to the second cellular telephone device B 4  owned by the user Z, from among the first identification/associated information stored in the first identification/associated information storage unit  431  of the memory  44 . In the present example, the first selected information is a mail address of the user X. In addition, the selection unit  421  stores the first selected information in the first selected information storage unit  432  of the memory  44 . 
     In Step ST 512 , in a case in which the first selected information is the first identification/associated information, the reply request unit  422  of the CPU  45  causes the radio communication unit  200  to transmit, to the first cellular telephone device A 4 , information (reply request information) for requesting a reply regarding whether to permit transmission of the first selected information. Here, the reply request information is stored in the reply request information storage unit  433  of the memory  44 . 
     In the present example, the reply request unit  422  transmits mail (reply request mail) for requesting a reply regarding whether to permit transmission of the first selected information (a mail address) to the user X. As shown in  FIG. 30 , this reply request mail includes, for example, a message stating that “Your (the user X&#39;s) mail address will be transmitted to the user Z. Do you approve? OK/NG”, which requests confirmation and reply, and a profile of the user Z (for example, “the user Z is a colleague of the user Y”). 
     In Step ST 513 , the timer  80  measures (times) a period of time (elapsed time) since the radio communication unit  200  transmitted the reply request information (reply request mail). 
     In Step ST 514 , when the elapsed time measured by the timer  80  exceeds a predetermined period of time (for example, 5 minutes), the timer  80  terminates the timing. 
     When the timer  80  terminates the timing, in Step ST 525 , the first transmission permission unit  423  does not permit transmission of the first identification/associated information to the second cellular telephone device B 4 . 
     Thereafter, in Step ST 516 , the encryption processing unit  424  encrypts the first identification/associated information to generate encryption information. In addition, the encryption processing unit  424  stores the encryption information thus generated in the encryption information storage unit  435  of the memory  44 . 
     In Step ST 517 , the first notification information transmission unit  426  causes the radio communication unit  200  to transmit the first notification information to the server W. The first notification information is information that includes: the notification information for notifying of the fact that the first identification/associated information has been transmitted to the second cellular telephone device B 4 ; the first identification information; and the second identification information. 
     In Step ST 518 , the server side first storage unit  941  of the server W stores the first identification information, the second identification information and the like that are included in the first notification information received by the server side communication unit  960 . 
     Moreover, in Step ST 519 , the encryption information transmission permission unit  425  permits the infrared communication unit  20  to transmit the encryption information, which is generated by the encryption processing unit  424  and stored in the encryption information storage unit  435 , to the second cellular telephone device B 4 . As a result, the infrared communication unit  20  of the main cellular telephone device  1 D transmits the encryption information to the second cellular telephone device B 4 . 
     In Step ST 520 , the encryption information is stored in the second communication terminal side encryption information storage unit  471  of the second cellular telephone device B 4 . 
     When the infrared communication unit  20 B receives the encryption information, in Step ST 521 , the second communication terminal side erasing unit  463  causes the timer  80 B as the second communication terminal side timing unit to start measuring the time. As a result, the timer  80 B measures (times) a period of time (elapsed time) since the infrared communication unit  20 B received the encryption information. 
     In addition, in a case in which the server side communication unit  960  receives the first notification information, in Step ST 522 , the second communication information transmission unit  911  of the server W causes the server side communication unit  960  to transmit the second notification information to the first cellular telephone device A 4 . The second notification information includes: the notification information for notifying of the fact that the first identification/associated information has been encrypted and transmitted from the main cellular telephone device  1 D to the second cellular telephone device B 4 ; the second identification information stored in the server side first storage unit  941 ; and the server address information stored in the server side second storage unit  942 . 
     In the present example, as shown in  FIG. 31 , the second communication information transmission unit  911  transmits the second notification information mail stating that “The user Y has transmitted the encryption information encrypted from your (the user X&#39;s) mail address to the user Z. If you permit decryption of the encryption information, please transmit decryption key information to the server W, and if you do not permit decryption, please transmit non-permission information to the server W.” 
     In Step ST 523 , the first communication terminal side second storage unit  452  stores the second identification information, the server address information and the like that are included in the second notification information received by the radio communication unit  200 A. 
     Thereafter, in the first cellular telephone device A 4  that has received the second notification information mail, according to an operation of the user X, in Step ST 531 , the first communication terminal side decryption key information transmission unit  441  of the first cellular telephone device A 4  causes the radio communication unit  200 A to transmit the decryption key information stored in the first communication terminal side decryption key information storage unit  453  to the server W. 
     In Step ST 532 , the server side decryption key information storage unit  943  stores the decryption key information transmitted from the first cellular telephone device A 4 . 
     In this way, in a state in which the decryption key information is stored in the server W, in the second cellular telephone device B 4 , according to an operation of the user Z, in Step ST 541 , the second communication terminal side decryption key information request unit  462  causes the radio communication unit  200 B to transmit the first request information for requesting the decryption key information to the server W. 
     In Step ST 542 , in a case in which the server side communication unit  960  receives the first request information, the server side determination unit  913  determines whether the decryption key information is stored in the server side decryption key information storage unit  943 . In a case in which the server side determination unit  913  determines that the decryption key information is stored in the server side decryption key information storage unit  943  (YES), the processing advances to Step ST 543 . In a case in which the server side determination unit  913  determines that the decryption key information is not stored in the server side decryption key information storage unit  943  (NO), the processing advances to Step ST 644  (see  FIG. 32 ). It should be noted that Example 4-2 is an example in a case in which the server side determination unit  913  determines that the decryption key information is not stored in the server side decryption key information storage unit  943  (NO), and will be described later. 
     In a case in which the server side communication unit  960  receives the first request information, and the server side determination unit  913  determines that the decryption key information is stored in the server side decryption key information storage unit  943  (YES), in Step ST 543 , the server side decryption key information transmission unit  912  causes the server side communication unit  960  to transmit the decryption key information stored in the server side decryption key information storage unit  943  to the second cellular telephone device B 4 . 
     In a case in which the server side determination unit  913  determines that the decryption key information is stored in the server side decryption key information storage unit  943  (YES), in Step ST 551 , the decryption key information is stored in the second communication terminal side decryption key information storage unit  473  of the second cellular telephone device B 4 . 
     In a case in which the second cellular telephone device B 4  receives the decryption key information before the elapsed time measured by the timer  80 B reaches a predetermined period of time (for example, 12 hours), in Step ST 552 , the decryption processing unit  461  of the second cellular telephone device B 4  decrypts the encryption information based on the decryption key information to generate the first identification/associated information. As a result, the first identification/associated information is obtained in the second cellular telephone device B 4  (the user Z). 
     Example 4-2 
     Next, Example 4-2 is described. Example 4-2 is an example in a case in which the server side determination unit  913  determines that the decryption key information is not stored in the server side decryption key information storage unit  943  (NO). Since Steps ST 611  to ST 623  in Example 4-2 are similar to Steps ST 511  to ST 523  in Example 4-1, respectively, descriptions thereof are omitted. 
     Example 4-2 is described from the step after Step ST 623 . 
     Steps ST 611  to ST 623  in Example 4-2 are performed similarly to Steps ST 511  to ST 523  in Example 4-1. 
     In Example 4-1, the decryption key information is already stored in the server W (Step ST 532 ) when the second cellular telephone device B 4  transmits the first request information (Step ST 541 ); on the other hand, in Example 4-2, the decryption key information is not stored in the server W (Step ST 632  is not being performed) when the second cellular telephone device B 4  transmits the first request information (Step ST 641 ). 
     In this way, in a state in which the decryption key information is not stored in the server W, in the second cellular telephone device B 4 , according to an operation of the user Z, in Step ST 641 , the second communication terminal side decryption key information request unit  462  causes the radio communication unit  200 B to transmit the first request information for requesting the decryption key information to the server W. 
     In Step ST 642 , in a case in which the server side communication unit  960  receives the first request information, the server side determination unit  913  determines whether the decryption key information is stored in the server side decryption key information storage unit  943 . In Example 4-2, since the decryption key information is not stored in the server side decryption key information storage unit  943 , the server side determination unit  913  determines that the decryption key information is not stored in the server side decryption key information storage unit  943  (NO), and the processing advances to Step ST 644 . 
     In a case in which the server side determination unit  913  determines that the decryption key information is not stored in the server side decryption key information storage unit  943  (NO), in Step ST 644 , the fourth notification information transmission unit  916  causes the server side communication unit  960  to transmit, to the second cellular telephone device B 4 , the fourth notification information for notifying of the fact that the decryption key information is not stored in the server side decryption key information storage unit  943 . 
     Moreover, in a case in which the server side determination unit  913  determines that the decryption key information is not stored in the server side decryption key information storage unit  943  (NO), the server side decryption key information request unit  914  causes the server side communication unit  960  to transmit, to the first cellular telephone device A 4 , the second request information for requesting transmission of the encryption information. 
     In the present example, as shown in  FIG. 33 , the server side decryption key information request unit  914  transmits the second request information mail stating that “A request for decrypting the encryption information of your (the user X&#39;s) mail address has arrived from the user Z. If you permit decryption of the encryption information, please transmit decryption key information to the server W, and if you do not permit decryption, please transmit non-permission information to the server W.” 
     Thereafter, in the first cellular telephone device A 4  that received the second request information mail, in a case in which the user permits decryption of the encryption information, as shown in  FIG. 32 , according to an operation of the user X, in Step ST 631 , the first communication terminal side decryption key information transmission unit  441  of the first cellular telephone device A 4  causes the radio communication unit  200 A to transmit the decryption key information stored in the first communication terminal side decryption key information storage unit  453  to the server W. 
     In Step ST 632 , the server side decryption key information storage unit  943  stores the decryption key information transmitted from the first cellular telephone device A 4 . 
     In a case in which the server side communication unit  960  receives decryption key information, in Step ST 646 , the third notification information transmission unit  915  causes the server side communication unit  960  to transmit, to the second cellular telephone device B 4 , the third notification information for notifying of the fact that the decryption key information is stored in the server side decryption key information storage unit  943 . 
     In the present example, as shown in  FIG. 34 , the third notification information transmission unit  915  transmits the third notification information mail stating that “The decryption key of the encryption information has been registered with the server W. The decryption key can be obtained from the server W”. 
     In this way, after the second cellular telephone device B 4  has confirmed that the decryption key information is registered (stored) in the server W, according to an operation of the user Z in the second cellular telephone device B 4 , in Step ST 641 - 2 , the second communication terminal side decryption key information request unit  462  causes the radio communication unit  200 B to transmit the first request information for requesting the decryption key information to the server W. 
     It should be noted that the suffix “−2” added to the end of the three-digit step number denotes that the same step is performed twice in the example. 
     In Step ST 642 - 2 , in a case in which the server side communication unit  960  receives the first request information, the server side determination unit  913  determines whether the decryption key information is stored in the server side decryption key information storage unit  943 . In this case, the server side determination unit  913  determines that the decryption key information is stored in the server side decryption key information storage unit  943  (YES), and the processing advances to Step ST 643 . 
     In a case in which the server side communication unit  960  receives the first request information, and the server side determination unit  913  determines that the decryption key information is stored in the server side decryption key information storage unit  943  (YES), in Step ST 643 , the server side communication unit  960  is caused to transmit the decryption key information stored in the server side decryption key information storage unit  943  to the second cellular telephone device B 4 . 
     In a case in which the server side determination unit  913  determines that the decryption key information is stored in the server side decryption key information storage unit  943  (YES), in Step ST 651 , the decryption key information is stored in the second communication terminal side decryption key information storage unit  473  of the second cellular telephone device B 4 . 
     In a case in which the second cellular telephone device B 4  receives the decryption key information before the elapsed time measured by the timer  80 B reaches a predetermined period of time (for example, 12 hours), in Step ST 652 , the decryption processing unit  461  of the second cellular telephone device B 4  decrypts the encryption information based on the decryption key information to generate the first identification/associated information. As a result, the first identification/associated information is obtained in the second cellular telephone device B 4  (the user Z). 
     Example 4-3 
     Next, Example 4-3 is described. Example 4-3 is an example in which the user X transmits non-permission information to the server W. Since Steps ST 711  to ST 723  in Example 4-3 are similar to Steps ST 511  to ST 523  in Example 4-1, respectively, descriptions thereof are omitted. 
     Example 4-3 is described from the step after Step ST 723 . 
     Steps ST 711  to ST 723  in Example 4-3 are performed similarly to Steps ST 511  to ST 523 , ST 531  and ST 532  in Example 4-1. 
     Example 4-3 is mainly different from Example 4-1 in that the first cellular telephone device A 4  transmits non-permission information to the server W (Step ST 761 ). 
     In the first cellular telephone device A 4  that received the second notification information mail, in a case in which the user X decided not to permit transmission of the decryption key information to the user Z, according to an operation of the user X in the first cellular telephone device A 4 , in Step ST 761 , the non-permission information transmission unit  442  causes the radio communication unit  200  to transmit the non-permission information to the server W. The non-permission information is information for not permitting transmission of the decryption key information stored in the first communication terminal side decryption key information storage unit  453  to the second cellular telephone device B 4 . 
     When the server side communication unit  960  of the server W receives the non-permission information, in Step ST 762 , the non-permission information is stored in the non-permission information storage unit  947 . 
     When the server side communication unit  960  of the server W receives the non-permission information, the server side erasing unit  917  starts timing by the timer  980 . 
     In Example 4-3, in a state in which the non-permission information is stored in the non-permission information storage unit  947 , in Step ST 741 , according to an operation of the user Z in the second cellular telephone device B 4 , the second communication terminal side decryption key information request unit  462  causes the radio communication unit  200 B to transmit the first request information for requesting the decryption key information to the server W. 
     In a case in which the server side communication unit  960  receives the non-permission information, in Step ST 763 , the first erasing instruction information transmission unit  918  causes the server side communication unit  960  to transmit the first erasing instruction information to the second cellular telephone device B 4 . The first erasing instruction information includes an instruction to erase the encryption information stored in the second communication terminal side encryption information storage unit  471 . 
     In the second cellular telephone device B 4  that received the first erasing instruction information, in a case in which the radio communication unit  200 B receives the first erasing instruction information, in Step ST 764 , the second communication terminal side erasing unit  463  erases the encryption information stored in the second communication terminal side encryption information storage unit  471 . 
     Moreover, in a case in which the server side communication unit  960  receives the non-permission information, in Step ST 765 , the server side erasing unit  917  erases the decryption key information stored in the server side decryption key information storage unit  943 . 
     Example 4-4 
     Next, Example 4-4 is described. Example 4-4 is an example in a case in which a predetermined period of time elapsed since the second cellular telephone device B 4  received the encryption information, and thus the encryption information stored in the second cellular telephone device B 4  is automatically erased. Since Steps ST 811  to ST 823 , ST 861  and ST 862  in Example 4-4 are similar to Steps ST 711  to ST 723 , ST 761  and ST 762  in Example 4-3, respectively, descriptions thereof are omitted. 
     Example 4-2 is described from Step ST 823 . 
     Steps ST 811  to ST 823 , ST 861  and ST 862  in Example 4-4 are performed similarly to Steps ST 711  to ST 723 , ST 761  and ST 762  in Example 4-3. 
     As shown in  FIG. 36 , in Step ST 862 , the non-permission information storage unit  947  stores the non-permission information transmitted from the first cellular telephone device A 4 . 
     In the second cellular telephone device B 4 , when a predetermined period of time (for example, 12 hours) elapses since the timer  80 B started timing, in Step ST 866 , the timing by the timer  80 B is terminated. 
     Thereafter, in Step ST 867 , the second communication terminal side erasing unit  463  erases the encryption information stored in the second communication terminal side encryption information storage unit  471  of the memory  44 B. 
     Example 4-5 
     Next, Example 4-5 is described. Example 4-5 is an example in a case in which the first cellular telephone device A 4  (the user X) transmits a permission reply within a predetermined period of time after reply request information (reply request mail) is transmitted. Since Steps ST 911  to ST 913  in Example 4-5 are similar to Steps ST 511  to ST 513  in Example 4-1, respectively, descriptions thereof are omitted. 
     Example 4-5 is described from Step ST 913 . 
     As shown in  FIG. 37 , in Step ST 913 , the timer  80  of the second cellular telephone device B 4  starts measuring (timing) a period of time since the reply request mail was transmitted (see  FIG. 30 ). 
     When the user X, who owns the first cellular telephone device A 4 , confirms the reply request mail, and the user X performs an operation (selecting “OK”) to transmit a reply (permission reply) for permitting transmission of the first identification/associated information, in Step ST 961 , the CPU  45 A of the first cellular telephone device A 4  causes the radio communication unit  200 A to transmit permission reply mail as a permission reply. As a result, the radio communication unit  200 A of the first cellular telephone device A 4  transmits the permission reply mail. 
     In a case in which the second cellular telephone device B 4  receives the permission reply mail via the radio communication unit  200  before the elapsed time measured by the timer  80  reaches a predetermined period of time (for example, 5 minutes), in Step ST 962 , the first transmission permission unit  423  permits the infrared communication unit  20  to transmit the first identification/associated information selected by the selection unit  421  (the first selected information stored in the first selected information storage unit  432 ) to the second cellular telephone device B 4 . 
     Subsequently, in Step ST 963 , the main cellular telephone device  1 D transmits the first identification/associated information (a mail address of the user X) to the second cellular telephone device B 4  via the infrared communication unit  20 . 
     As described above, for example, the following effects are achieved according to the communication system S of the present embodiment. 
     For example, when the first identification/associated information (the mail address of the user X) being encrypted (encryption information) is transmitted to the user Z (the second cellular telephone device B 4 ) in a state in which permission of the user X is not obtained, and the permission (the decryption key information) of the user X is subsequently obtained, the decryption key information for decrypting the encryption information can be transmitted to the user Z (the second cellular telephone device B 4 ) via the server W. 
     Moreover, since transactions among the cellular telephone devices are mainly performed by the server W, the processing load on each cellular telephone device is small. 
     In addition, as in Example 4-2, even in a case in which the decryption key information is not stored in the server W, the decryption key information can be requested to the first cellular telephone device A 4  (the user X) by way of the second request information mail via the server W. 
     Furthermore, as in Examples 4-3 and 4-4, in a case in which the first cellular telephone device A 4  (the user X) has transmitted the non-permission information to the server W, and in a case in which the predetermined period of time has elapsed, it is possible to erase the decryption key information stored in the server W and the encryption information stored in the second cellular telephone device B 4 . This is preferable in terms of the security of the first identification/associated information. 
     Next, the communication system S of a fifth embodiment is described. With reference to  FIGS. 38 to 41 , a description is mainly provided for the functional configuration relating to the memory  44  in a main cellular telephone device  1 E, a first cellular telephone device A 5 , and a second cellular telephone device B 5 , as well as the functional configuration relating to the CPU  45  in the main cellular telephone device  1 E, the first cellular telephone device A 5 , and the second cellular telephone device B 5 . In the present embodiment, descriptions are omitted for configurations similar to those in the fourth embodiment shown in  FIGS. 25 to 27 . 
       FIG. 38  is a functional block diagram illustrating the functional configuration of the main cellular telephone device  1 E according to the fifth embodiment.  FIG. 39  is a functional block diagram illustrating the functional configuration of the first cellular telephone device A 5  according to the fifth embodiment.  FIG. 40  is a functional block diagram illustrating the functional configuration of the second cellular telephone device B 5  according to the fifth embodiment. 
     As shown in  FIG. 38 , in the main cellular telephone device  1 E, an encryption processing unit  524  of the CPU  45  encrypts the first identification information of the first cellular telephone device A 5  to generate the first encryption information, and encrypts the second associated information of the second cellular telephone device B 5  to generate the second encryption information. 
     Moreover, in the main cellular telephone device  1 E, the encryption information storage unit  535  of the memory  44  stores the first encryption information and the second encryption information generated in the encryption processing unit  524 . 
     In addition, in the main cellular telephone device  1 E, a decryption key information storage unit  537  of the memory  44  stores the first decryption key information including a first decryption key for decrypting the first encryption information, and the second decryption key information including a second decryption key for decrypting the second encryption information. 
     As shown in  FIG. 39 , in the first cellular telephone device A 5 , the CPU  45 A includes a first communication terminal side decryption processing unit  544 , and the memory  44 A includes a first communication terminal side encryption information storage unit  551  and a first communication terminal side decryption key information storage unit  552 . 
     The first communication terminal side decryption processing unit  544  decrypts the second encryption information based on the second decryption key information to generate the second associated information. 
     The first communication terminal side encryption information storage unit  551  stores the second encryption information. 
     The first communication terminal side decryption key information storage unit  552  stores the first decryption key information. 
     As shown in  FIG. 40 , in the second cellular telephone device B 5 , the second CPU  45 B includes a second communication terminal side decryption processing unit  561 , and the second memory  44 B includes a second communication terminal side decryption key information storage unit  572 . 
     The second communication terminal side decryption processing unit  561  decrypts the first encryption information based on the first decryption key information to generate the first identification information. 
     The second communication terminal side decryption key information storage unit  572  stores the second decryption key information. 
     Operations relating to the communication system S of the fifth embodiment are described with reference to  FIG. 41 .  FIG. 41  is a sequence diagram showing operations relating to the communication system S of the fifth embodiment. 
     Since Steps ST 1011  to ST 1015  in the operations relating to the communication system S of the fifth embodiment are similar to Steps ST 231  to ST 235  in the second embodiment, respectively, descriptions thereof are omitted. 
     In Step ST 1015 , in a case in which the elapsed time measured by the timer  80  exceeds a predetermined period of time (for example, 5 minutes), and thus the first transmission permission unit  523  does not permit transmission of the first identification/associated information to the second cellular telephone device B 5 , in Step ST 1016 , the encryption processing unit  524  encrypts the first identification information to generate the first encryption information, and encrypts the second associated information to generate the second encryption information. In addition, the encryption processing unit  524  stores the first encryption information and the second encryption information thus generated in the encryption information storage unit  535  of the memory  44 . 
     In Step ST 1017 , the first transmission permission unit  532  permits the radio communication unit  200  to transmit, to the second cellular telephone device B 5 , the first encryption information that is generated by the encryption processing unit  524  and stored in the encryption information storage unit  535 , and the second decryption key information stored in the decryption key information storage unit  537 . As a result, the first encryption information and the second decryption key information are transmitted from the radio communication unit  200  of the main cellular telephone device  1 E to the second cellular telephone device B 5 . In addition, the second cellular telephone device B 5 , which received the first encryption information and the second decryption key information from the main cellular telephone device  1 E, stores the first encryption information in the second communication terminal side encryption information storage unit  571 , and stores the second decryption key information in the second communication terminal side decryption key information storage unit  572 . 
     After the first encryption information is transmitted to the second cellular telephone device B 5 , in Step ST 1018 , the second notification unit  526  notifies the first cellular telephone device A 5  of information of the fact that the encrypted first identification/associated information (first encryption information) has been transmitted to the user Z, and information for requesting permission for transmitting the first decryption key or the like for decrypting the first encryption information to the user Z. 
     In Step ST 1019 , the first transmission permission unit  532  permits the radio communication unit  200  to transmit, to the first cellular telephone device A 5 , the second encryption information that is generated by the encryption processing unit  524  and stored in the encryption information storage unit  535 , and the first decryption key information stored in the decryption key information storage unit  537 . As a result, the second encryption information and the first decryption key information are transmitted from the radio communication unit  200  of the main cellular telephone device  1 E to the first cellular telephone device A 5 . The first cellular telephone device A 5 , which received the second encryption information and the first decryption key information from the main cellular telephone device  1 E, stores the second encryption information in the first communication terminal side encryption information storage unit  551 , and stores the first decryption key information in the first communication terminal side decryption key information storage unit  552 . 
     In the first cellular telephone device A 5  (the user X), in a case in which the encryption information transmission completion notification mail is received, and the user X determines that the first decryption key information may be transmitted to the second cellular telephone device B 5  (the user Z), according to an operation of the user X, the first communication terminal side decryption key information transmission permission unit  541  permits the radio communication unit  200 A of the first cellular telephone device A 5  to transmit the first decryption key information stored in the decryption key information storage unit  537  to the second cellular telephone device B 5 . As a result, in Step ST 1020 , the radio communication unit  200 A of the first cellular telephone device A 5  transmits the first decryption key information to the second cellular telephone device B 5 . 
     When the second cellular telephone device B 5  receives the first decryption key information, in Step ST 1021 , the second communication terminal side decryption processing unit  561  decrypts the first encryption information based on the first decryption key information to generate the first identification information. As a result, the first identification information is obtained in the second cellular telephone device B 5  (the user Z). 
     When the first encryption information is decrypted and the first identification information is generated in second cellular telephone device B 5 , in Step ST 1022 , the second communication terminal side decryption key information transmission unit  562  causes the radio communication unit  200  to transmit, to the first cellular telephone device A 5 , the second decryption key information stored in the second communication terminal side decryption key information storage unit  572 . 
     When the first cellular telephone device A 5  receives the second decryption key information, in Step ST 1023 , the first communication terminal side decryption processing unit  544  decrypts the second encryption information based on the second decryption key information to generate the second associated information. As a result, the second associated information is obtained in the first cellular telephone device A 5  (the user X). 
     In this way, in the fifth embodiment, after transmitting the second encryption information and the first decryption key information to the first cellular telephone device A 5  (the user X), and transmitting the first encryption information and the second decryption key information to the second cellular telephone device B 5  (the user Z), the transactions of the first decryption key information and the second decryption key information can be performed as transactions between the first cellular telephone device A 5  (the user X) and the second cellular telephone device B 5  (the user Z) without involving the main cellular telephone device  1 E (the user Y). Therefore, the load on the main cellular telephone device  1 E (the user Y) is reduced. 
     Moreover, in the fifth embodiment, since the identification information of the first cellular telephone device A 5  (the user X) and the associated information of the second cellular telephone device B 5  (the user Z) are encrypted, the information transactions can be performed in a state ensuring the security of each of the first cellular telephone device A 5  (the user X) and the second cellular telephone device B 5  (the user Z). 
     Next, the communication system S of a sixth embodiment is described. The functional configuration relating to the memory  44  in a server W 1  and the functional configuration relating to the CPU  45  are mainly described with reference to  FIG. 42 . In the present embodiment, descriptions are omitted for configurations similar to those in the fourth embodiment shown in  FIGS. 22 to 28  and the fifth embodiment shown in  FIGS. 38 to 40 .  FIG. 28  is a functional block diagram illustrating the functional configuration of the server W 1  according to the sixth embodiment. 
     As shown in  FIG. 42 , in the server W 1 , the CPU  1010  includes a server side decryption key information transmission unit  1011 , and the memory  1040  includes the server side decryption key information storage unit  1041 . 
     The server side decryption key information transmission unit  1011  transmits the first decryption key information to the second cellular telephone device B 6 , and transmits the first decryption key information to the second cellular telephone device B 6 . 
     The server side decryption key information storage unit  1041  stores the first decryption key information and the second decryption key information. 
     Moreover, the server side determination unit  1012  determines whether the server side communication unit  960  has received the first decryption key information and the second decryption key information. 
     When a predetermined time elapses, a server side erasing unit  1013  erases the first decryption key information and the second decryption key information stored in the server side decryption key information storage unit  1041 . 
     Operations relating to the communication system S of the sixth embodiment are described with reference to  FIG. 43 .  FIG. 43  is a sequence diagram showing operations relating to the communication system S of the sixth embodiment. 
     Since Steps ST 1111  to ST 1115  in the operations relating to the communication system S of the sixth embodiment are similar to Steps ST 711  to ST 715  in the fourth embodiment, respectively, descriptions thereof are omitted. 
     In Step ST 1115 , in a case in which the elapsed time measured by the timer  80  exceeds a predetermined period of time (for example, 5 minutes), and thus the first transmission permission unit  523  does not permit transmission of the first identification/associated information to the second cellular telephone device B 6 , in Step ST 1116 , the encryption processing unit  524  encrypts the first identification information to generate the first encryption information, and encrypts the second associated information to generate the second encryption information. In addition, the encryption processing unit  524  stores the first encryption information and the second encryption information thus generated in the encryption information storage unit  535  of the memory  44 . 
     In Step ST 1117 , the first transmission permission unit  532  permits the radio communication unit  200  to transmit, to the second cellular telephone device B 6 , the first encryption information that is generated by the encryption processing unit  524  and stored in the encryption information storage unit  535 , and the second decryption key information stored in the decryption key information storage unit  537 . As a result, the first encryption information and the second decryption key information are transmitted from the radio communication unit  200  of the main cellular telephone device  1 F to the second cellular telephone device B 6 . In addition, the second cellular telephone device B 6 , which received the first encryption information and the second decryption key information from the main cellular telephone device  1 F, stores the first encryption information in the second communication terminal side encryption information storage unit  571 , and stores the second decryption key information in the second communication terminal side decryption key information storage unit  572 . 
     After the first encryption information is transmitted to the second cellular telephone device B 6 , in Step ST 1118 , the second notification unit  526  notifies the first cellular telephone device A 6  of information of the fact that the encrypted first identification information (the first encryption information) has been transmitted to the user Z, and information for requesting permission for transmitting the first decryption key or the like for decrypting the first encryption information to the user Z. 
     Moreover, in Step ST 1018 , the first transmission permission unit  532  permits the radio communication unit  200  to transmit, to the first cellular telephone device A 6 , the second encryption information that is generated by the encryption processing unit  524  and stored in the encryption information storage unit  535 , and the first decryption key information stored in the decryption key information storage unit  537 . As a result, the second encryption information and the first decryption key information are transmitted from the radio communication unit  200  of the main cellular telephone device  1 F to the first cellular telephone device A 6 . The first cellular telephone device A 6 , which has received the second encryption information and the first decryption key information from the main cellular telephone device  1 F, stores the second encryption information in the first communication terminal side encryption information storage unit  551 , and stores the first decryption key information in the first communication terminal side decryption key information storage unit  552 . 
     After storing the second encryption information and the first decoded information, the first communication terminal side decryption key information transmission permission unit  541  permits the radio communication unit  200 A to transmit, to the server W 1 , the first decryption key information stored in the first communication terminal side decryption key information storage unit  552 . As a result, in Step ST 1119 , the radio communication unit  200 A of the first cellular telephone device A 6  transmits the first decryption key information to the server W 1 . 
     After receiving the first encryption information, in Step ST 1120 , the second communication terminal side decryption key information transmission unit  562  causes the radio communication unit  200 B to transmit the second decryption key information stored in the second communication terminal side decryption key information storage unit  572  to the server W 1 . 
     In Step ST 1121 , in a case in which the server side communication unit  960  receives the first request information, the server side determination unit  1012  determines whether the decryption key information is stored in the server side decryption key information storage unit  1041 . In a case in which the server side determination unit  1012  determines that the first decryption key information and the second decryption key information are stored in the server side decryption key information storage unit  1041  (YES), the processing advances to Step ST 1122 . In a case in which the server side determination unit  1012  determines that the decryption key information is not stored in the server side decryption key information storage unit  1041  (NO), the server side erasing unit  1013  erases information stored in the server side decryption key information storage unit  1041  in a predetermined period of time. 
     In a case in which the server side determination unit  1012  determines that the first decryption key information and the second decryption key information are stored in the server side decryption key information storage unit  1041  (YES), in Step ST 1122 , the server side decryption key information transmission unit  1011  causes the server side communication unit  960  to transmit the first decryption key information stored in the server side decryption key information storage unit  1041  to the second cellular telephone device B 6 . 
     After transmitting the first decryption key information stored in the server side decryption key information storage unit  1041  to the second cellular telephone device B 6 , in Step ST 1123 , the server side decryption key information transmission unit  1011  causes the server side communication unit  960  to transmit the second decryption key information stored in the server side decryption key information storage unit  1041  to the first cellular telephone device A 6 . 
     When the second cellular telephone device B 6  receives the first decryption key information, in Step ST 1124 , the second communication terminal side decryption processing unit  561  decrypts the first encryption information based on the first decryption key information to generate the first identification information. As a result, the first identification information is obtained in the second cellular telephone device B 6  (the user Z). 
     When the first cellular telephone device A 6  receives the second decryption key information, in Step ST 1125 , the first communication terminal side decryption processing unit  544  decrypts the second encryption information based on the second decryption key information to generate the second associated information. As a result, the second associated information is obtained in the first cellular telephone device A 6  (the user X). 
     In this way, in the sixth embodiment, after transmitting the second encryption information and the first decryption key information to the first cellular telephone device A 6  (the user X), and transmitting the first encryption information and the second decryption key information to the second cellular telephone device B 6  (the user Z), the transactions of the first decryption key information and the second decryption key information can be performed through transactions between the first cellular telephone device A 6  (the user X) and the second cellular telephone device B 6  (the user Z) via the server W 1  without involving the main cellular telephone device  1 F (the user Y). Therefore, the load on the main cellular telephone device  1 F (the user Y) is reduced. 
     Moreover, in the sixth embodiment, since the identification information of the first cellular telephone device A 6  (the user X) and the associated information of the second cellular telephone device B 6  (the user Z) are encrypted, the information transactions can be performed in a state of ensuring the security of each of the first cellular telephone device A 6  (the user X) and the second cellular telephone device B 6  (the user Z). 
     It should be noted that each embodiment described above can be configured such that the address book information of the sender is added to (or associated with) information (for example, the identification information, the reply request information, the encryption information, etc.) to be transmitted. In this case, the address book information to be added is preferably the identification/associated information obtained by the sender from another cellular telephone device, and is preferably configured as information that cannot be browsed by operation of the cellular telephone device of the user. 
     With such a configuration, in the communication system S, for example, if the address book information of the main cellular telephone device  1  (the user Y) is added to the transmission permission information or the like from the main cellular telephone device  1  (the user Y) when the main cellular telephone device  1  (user Y) attempts to transmit the identification information of the first cellular telephone device A (the user X) to the second cellular telephone device B (the user Z), it is possible to implement a configuration in which, based on the address book information thus added, the first cellular telephone device A (the user X) searches for information (for example, the associated information such as a name) of the second cellular telephone device B (the user Z) included in the transmission permission information. Accordingly, in the communication system S, it is possible to provide the user X of the first cellular telephone device A with considerations for determining whether to permit transmission by using the results of searching the address book information. 
     In addition, the identification/associated information configuring the address book information is associated with information on the time when the identification/associated information was obtained (received), thereby making it possible to provide considerations for further determining the relationship between the sender (for example, the main cellular telephone device  1  (the user Y)) and the cellular telephone device corresponding to the identification/associated information of the address book information (for example, the second cellular telephone device (the user Z)). 
     Furthermore, in the communication system S, each cellular telephone device may be configured such that the address book information of the sender is added to the identification/associated information when the identification/associated information is obtained (received). With the communication system S configured in this way, for example, in a case in which the main cellular telephone device  1  (the user Y) transmits the identification/associated information of the first cellular telephone device A (user X) to the second cellular telephone device B (the user Z), as shown in  FIG. 44 , it is possible to implement a configuration such that the main cellular telephone device  1  (the user Y) causes the first cellular telephone device A (the user X) to add the address book information of the second cellular telephone device B (the user Z), which was obtained when receiving the identification/associated information from the second cellular telephone device B (the user Z), to the information for permitting transmission, in addition to the information of the second cellular telephone device B (user Z) and the main cellular telephone device  1  (the user Y). In this case, it is preferable to implement a configuration such that the address book information is updated by comparing the already obtained address book information (for example, the address book information obtained when receiving the identification/associated information) and the newly obtained address book information (for example, the address book information obtained when receiving the transmission permission information). 
     In a case of configuring in this way, further to the address book of the main cellular telephone device  1  (the user Y), in the address book information of the second cellular telephone device B (the user Z), the first cellular telephone device A can be configured to search information (for example, information such as a name) of the main cellular telephone device  1  (the user Y) and the second cellular telephone device B (the user Z) for the address book information of the main cellular telephone device  1  (the user Y) and the second cellular telephone device B (the user Z). Accordingly, in the communication system S, using a search result thereof, it is possible to provide the user X with considerations for determining the relationship of the main cellular telephone device  1  (the user Y) and the second cellular telephone device B (the user Z). Although preferred embodiments have been described above, the present invention is not limited to the aforementioned embodiments, and can be implemented in various modes. For example, the cellular telephone device  1  is described as a communication terminal in the present embodiment; however, the present invention is not limited thereto, and the communication terminal may be a PHS (Personal Handyphone System), a PDA (Personal Digital Assistant), a portable navigation device, a notebook PC, or the like. 
     Moreover, in the present embodiment, the cellular telephone device  1  is described as being foldable via the connecting portion  4 ; however, instead of such a folder type, the cellular telephone device may be of: a slider type in which one of the bodies slides in one direction in a state in which the operation unit side body  2  and the display unit side body  3  are mutually superimposed; a rotating (turning) type in which one of the bodies is rotated around an axis line along the direction in which the operation unit side body  2  and the display unit side body  3  are superimposed; and a type (straight type) in which the operation unit side body  2  and the display unit side body  3  are disposed in one body without having a connecting portion. In addition, the cellular telephone device  1  may be of a so-called 2-axis hinge type that is openable and closable as well as rotatable. 
     In the aforementioned embodiments, the second communication unit (the radio communication unit  200 ) that performs communication by way of the second communication method communicating via the communication network is used for communication between the main cellular telephone device and the first cellular telephone device, and the first communication unit (the infrared communication unit  20 ) that performs communication by way of the first communication method communicating without the communication network is used for communication between the main cellular telephone device and the second cellular telephone device; however, it is not limited thereto. 
     APPENDICES 
     Appendix 1 
     A communication terminal, comprising: 
     a communication unit, 
     a first storage unit that stores first information related to a first communication terminal; 
     an information creation unit that creates information to be transmitted to a second communication terminal different from the first communication terminal via the communication unit; and 
     a control unit, 
     wherein the control unit includes: 
     a reply request unit that transmits, from the communication unit to the first communication terminal, information for requesting a reply regarding whether transmission of the created information is permitted, in a case in which the information created by the information creation unit includes a part or all of the first information; and 
     a first communication permission unit that transmits the created information from the communication unit to the second communication terminal, in a case in which a permission reply for permitting the created information to be transmitted from the first communication terminal is received via the communication unit. 
     Appendix 2 
     The communication terminal according to appendix 1, wherein the first information includes: first identification information corresponding to the first communication terminal; and first associated information associated with the first identification information. 
     Appendix 3 
     The communication terminal according to appendix 1 or 2, 
     wherein the communication unit includes: a first communication unit that performs communication by way of a first communication method for communicating with communication terminals without a communication network; and a second communication unit that performs communication by way of a second communication method for communicating with the communication terminals via the communication network, 
     wherein the control unit performs control such that the second communication unit is used preferentially to the first communication unit for communication with the first communication terminal. 
     Appendix 4 
     The communication terminal according to any one of appendices 1 to 3, wherein the information creation unit creates information to be transmitted to the second communication terminal, based on the first information stored in the first storage unit. 
     Appendix 5 
     A communication terminal, comprising: 
     a first communication unit that performs communication by way of a first communication method; 
     a second communication unit that performs communication by way of a second communication method different from the first communication method; 
     a first storage unit that stores first identification information corresponding to a first communication terminal, and first associated information associated with the first identification information; 
     a selection unit that selects information to be transmitted to a second communication terminal different from the first communication terminal via the first communication unit; 
     a reply request unit that causes the second communication unit to transmit information for requesting a reply regarding whether transmission of a part or all of the first identification information and the first associated information is permitted, to the first communication terminal identified by way of the first identification information, in a case in which the information selected by the selection unit is a part or all of the first identification information and the first associated information; and 
     a first communication permission unit that permits the first communication unit to transmit a part or all of the first identification information and the first associated information selected by the selection unit to the second communication terminal, in a case in which the second communication unit receives a permission reply from the first communication terminal for permitting transmission of the part or all of the first identification information and the first associated information. 
     Appendix 6 
     The communication terminal according to appendix 5, further comprising a timing unit that measures a period of time since the second communication unit transmitted the information for requesting a reply; 
     wherein, in a case in which the period of time measured by the timing unit exceeds a predetermined period of time, the first communication permission unit does not permit transmission of a part or all of the first identification information and the first associated information to the second communication terminal. 
     Appendix 7 
     The communication terminal according to appendix 6, further comprising a notification unit that causes, 
     in a case in which the period of time measured by the timing unit exceeds the predetermined period of time and the first communication permission unit does not permit transmission of a part or all of the first identification information and the first associated information to the second communication terminal, the second communication unit to transmit non-permission notification information for notifying of the fact that the first communication permission unit does not permit transmission of a part or all of the first identification information and the first associated information to the second communication terminal, to the first communication terminal identified by way of the first identification information. 
     Appendix 8 
     The communication terminal according to any one of appendices 5 to 7, 
     wherein, in a case in which the first communication permission unit does not permit transmission of a part or all of the first identification information and the first associated information, and subsequently the permission reply is received via the second communication unit, when the part or all of the first identification information and the first associated information is selected again, the first communication permission unit permits transmission of the part or all of the first identification information and the first associated information to the second communication terminal. 
     Appendix 9 
     A communication terminal, comprising: 
     a first communication unit that performs communication by way of a first communication method; 
     a second communication unit that performs communication by way of a second communication method different from the first communication method; 
     a first storage unit that stores first identification information corresponding to a first communication terminal, and first associated information associated with the first identification information; 
     a second storage unit that stores second identification information corresponding to a second communication terminal, and second associated information associated with the second identification information; 
     a selection unit that selects information to be transmitted to the second communication terminal via the first communication unit; 
     a reply request unit that causes the second communication unit to transmit information for requesting a reply regarding whether transmission of a part or all of the first identification information and the first associated information is permitted, to the first communication terminal identified by way of the first identification information, in a case in which the information selected by the selection unit is the part or all of the first identification information and the first associated information; 
     a timing unit that measures a period of time since the second communication unit transmitted the information for requesting a reply; 
     a first communication permission unit that does not permit the first communication unit to transmit a part or all of the first identification information and the first associated information to the second communication terminal in a case in which the period of time measured by the timing unit exceeds the predetermined period of time, and permits the first communication unit to transmit the part or all of the first identification information and the first associated information to the second communication terminal in a case in which the second communication unit receives a permission reply for permitting transmission of the part or all of the first identification information and the first associated information from the first communication terminal before the period of time measured by the timing unit exceeds the predetermined period of time; 
     an encryption processing unit that encrypts a part or all of the first identification information and the first associated information to generate encryption information, in a case in which the first communication permission unit does not permit transmission of the part or all of the first identification information and the first associated information due to the fact that the period of time measured by the timing unit exceeds the predetermined period of time; and 
     a second communication permission unit that permits the first communication unit to transmit the encryption information generated by the encryption processing unit to the second communication terminal identified by way of the second identification information. 
     Appendix 10 
     The communication terminal according to appendix 9, further comprising a third communication permission unit that permits the second communication unit to transmit decryption key information including a decryption key for decrypting the encryption information, in a case in which the encryption information is transmitted to the second communication terminal, and the second communication unit subsequently receives a permission reply from the first communication terminal. 
     Appendix 11 
     The communication terminal according to appendix 10, wherein the decryption key information includes usable number-of-times restriction information for restricting the number of times the decryption key can be utilized for decryption processing of the encryption information. 
     Appendix 12 
     A communication terminal, comprising: 
     a communication unit, 
     a first storage unit that stores first identification information corresponding to a first communication terminal, and first associated information associated with the first identification information; 
     a second storage unit that stores second identification information corresponding to a second communication terminal, and second associated information associated with the second identification information; 
     a selection unit that selects information to be transmitted to the second communication terminal via the communication unit; 
     a reply request unit that causes the communication unit to transmit information for requesting a reply regarding whether transmission of a part or all of the first identification information and the first associated information is permitted, to the first communication terminal identified by way of the first identification information, in a case in which the information selected by the selection unit is the part or all of the first identification information and the first associated information; 
     a timing unit that measures a period of time since the second communication unit transmitted the information for requesting a reply; 
     a first communication permission unit that permits the first communication unit to transmit a part or all of the first identification information and the first associated information selected by the selection unit, in a case in which the second communication unit receives a permission reply from the first communication terminal for permitting transmission of the part or all of the first identification information and the first associated information; and 
     a fourth communication permission unit that permits the first communication unit to transmit a part or all of the first identification information and the first associated information to the second communication terminal, and permits the communication unit to transmit the part or all of the second identification information and the second associated information to the first communication terminal identified by way of the first identification information, in a case in which the period of time measured by the timing unit exceeds the predetermined period of time. 
     Appendix 13 
     A communication terminal, comprising: 
     a first communication unit that performs communication by way of a first communication method; 
     a second communication unit that performs communication by way of a second communication method different from the first communication method; 
     a first storage unit that stores first identification information corresponding to a first communication terminal, and first associated information associated with the first identification information; 
     a second storage unit that stores second identification information corresponding to a second communication terminal, and second associated information associated with the second identification information; 
     a selection unit that selects information to be transmitted to the second communication terminal via the first communication unit; 
     a reply request unit that causes the second communication unit to transmit information for requesting a reply regarding whether transmission of a part or all of the first identification information and the first associated information is permitted, to the first communication terminal identified by way of the first identification information, in a case in which the information selected by the selection unit is the part or all of the first identification information and the first associated information; 
     a timing unit that measures a period of time since the second communication unit transmitted the information for requesting a reply; 
     a first communication permission unit that permits the first communication unit to transmit a part or all of the first identification information and the first associated information selected by the selection unit, in a case in which the second communication unit receives a permission reply from the first communication terminal for permitting transmission of the part or all of the first identification information and the first associated information; and 
     a fourth communication permission unit that permits the first communication unit to transmit a part or all of the first identification information and the first associated information to the second communication terminal, and permits the second communication unit to transmit the part or all of the second identification information and the second associated information to the first communication terminal identified by way of the first identification information, in a case in which the period of time measured by the timing unit exceeds the predetermined period of time. 
     Appendix 14 
     A communication terminal, comprising: 
     a communication unit, 
     a first storage unit that stores first identification information corresponding to a first communication terminal, and first associated information associated with the first identification information; 
     a second storage unit that stores second identification information corresponding to a second communication terminal, and second associated information associated with the second identification information; 
     a selection unit that selects information to be transmitted to the second communication terminal via the communication unit; 
     a reply request unit that causes the communication unit to transmit information for requesting a reply regarding whether transmission of a part or all of the first identification information and the first associated information is permitted, to the first communication terminal identified by way of the first identification information, in a case in which the information selected by the selection unit is the part or all of the first identification information and the first associated information; 
     a timing unit that measures a period of time since the communication unit transmitted the information for requesting a reply; 
     a first communication permission unit that permits the communication unit to transmit a part or all of the first identification information and the first associated information selected by the selection unit, in a case in which the communication unit receives a permission reply from the first communication terminal for permitting transmission of the part or all of the first identification information and the first associated information; and 
     a fifth communication permission unit that permits the communication unit to transmit a part or all of the second identification information and the second associated information to the first communication terminal identified by way of the first identification information, in a case in which the period of time measured by the timing unit exceeds the predetermined period of time. 
     Appendix 15 
     A communication terminal, comprising: 
     a first communication unit that performs communication by way of a first communication method; 
     a second communication unit that performs communication by way of a second communication method different from the first communication method; 
     a first storage unit that stores first identification information corresponding to a first communication terminal, and first associated information associated with the first identification information; 
     a second storage unit that stores second identification information corresponding to a second communication terminal, and second associated information associated with the second identification information; 
     a selection unit that selects information to be transmitted to the second communication terminal via the first communication unit; 
     a reply request unit that causes the second communication unit to transmit information for requesting a reply regarding whether transmission of a part or all of the first identification information and the first associated information is permitted, to the first communication terminal identified by way of the first identification information, in a case in which the information selected by the selection unit is the part or all of the first identification information and the first associated information; 
     a timing unit that measures a period of time since the second communication unit transmitted the information for requesting a reply; 
     a first communication permission unit that permits the first communication unit to transmit a part or all of the first identification information and the first associated information selected by the selection unit, in a case in which the second communication unit receives a permission reply from the first communication terminal for permitting transmission of the part or all of the first identification information and the first associated information; and 
     a fifth communication permission unit that permits the second communication unit to transmit a part or all of the second identification information and the second associated information to the first communication terminal identified by way of the first identification information, in a case in which the period of time measured by the timing unit exceeds the predetermined period of time. 
     Appendix 16 
     The communication terminal according to any one of appendices 3, 5, 6, 7, 8, 9, 10, 11, 13 or 15,
         wherein the first associated information includes transmission number-of-times information related to a number of times of transmission, and restricted number-of-times information including information related to a restricted number of times of transmission, and       

     wherein the first communication unit and/or the second communication unit do not transmit a part or all of the first identification information and the first associated information, in a case in which the transmission number of times included in the transmission number-of-times information is no more than the restricted number of times of transmission included in the restricted number-of-times information. 
     Appendix 17 
     A communication system, comprising: 
     a first communication terminal that can transmit predetermined decryption key information; 
     a main communication terminal that can transmit first identification information and first associated information associated with the first communication terminal, or encryption information encrypted from the first associated information, to a second communication terminal different from the first communication terminal; and 
     the second communication terminal that can receive the first identification information and the first associated information or the encryption information transmitted from the main communication terminal, 
     wherein the main communication terminal includes: 
     a first communication unit that performs communication by way of a first communication method; 
     a second communication unit that performs communication by way of a second communication method different from the first communication method; 
     a first storage unit that stores the first identification information corresponding to the first communication terminal, and the first associated information associated with the first identification information; 
     a second storage unit that stores second identification information corresponding to the second communication terminal, and second associated information associated with the second identification information; 
     a selection unit that selects information to be transmitted to the second communication terminal via the first communication unit; 
     a reply request unit that causes the second communication unit to transmit information for requesting a reply regarding whether transmission of a part or all of the first identification information and the first associated information is permitted, to the first communication terminal identified by way of the first identification information, in a case in which the information selected by the selection unit is the part or all of the first identification information and the first associated information; 
     a timing unit that measures a period of time since the second communication unit transmitted the information for requesting a reply; 
     a first communication permission unit that does not permit the first communication unit to transmit a part or all of the first identification information and the first associated information to the second communication terminal in a case in which the period of time measured by the timing unit exceeds the predetermined period of time, and permits the first communication unit to transmit the part or all of the first identification information and the first associated information to the second communication terminal in a case in which the second communication unit receives a permission reply for permitting transmission of the part or all of the first identification information and the first associated information from the first communication terminal before the period of time measured by the timing unit exceeds the predetermined period of time; 
     an encryption processing unit that encrypts a part or all of the first identification information and the first associated information to generate encryption information, in a case in which the first communication permission unit does not permit transmission of the part or all of the first identification information and the first associated information; and 
     a second communication permission unit that permits the first communication unit to transmit the encryption information generated by the encryption processing unit to the second communication terminal identified by way of the second identification information. 
     Appendix 18 
     The communication system according to appendix 17, further comprising: 
     wherein the second communication terminal includes: 
     a second communication terminal side first communication unit that can perform communication by way of the first communication method; 
     a second communication terminal side second communication unit that can communicate by way of the second communication method; and 
     a decryption key request unit that causes the second communication terminal side second communication unit to transmit request information for requesting transmission of decryption key information including a decryption key for decrypting the encryption information to the first communication terminal, in a case in which the second communication terminal side first communication unit receives the encryption information transmitted from the main communication terminal, 
     wherein the first communication terminal includes: 
     a first communication terminal side second communication unit that can communicate by way of the second communication method; 
     a decryption key information storage unit that stores the decryption key information including the decryption key for decrypting the encryption information; and 
     a first communication terminal side third communication permission unit that can permit the first communication terminal side second communication unit to transmit the decryption key information stored in the decryption key information storage unit to the second communication terminal, in a case in which the first communication terminal side second communication unit receives the information for requesting transmission of the decryption key information transmitted from the second communication terminal. 
     Appendix 19 
     The communication system according to appendix 18, 
     wherein the first communication terminal includes a first communication terminal side notification unit that causes the first communication terminal side second communication unit to transmit, to the main communication terminal, information for notifying of the fact that the decryption key information has been transmitted to the second communication terminal, in a case in which the first communication terminal side third communication permission unit transmits the decryption key information to the second communication terminal. 
     Appendix 20 
     The communication system according to appendix 18 or 19, 
     wherein the second communication terminal includes: 
     a second communication terminal side timing unit that measures a period of time since the second communication terminal side first communication unit received the encryption information transmitted from the main communication terminal; and 
     an erasing unit that erases the encryption information in a case in which the period of time measured by the second communication terminal side timing unit has passed a predetermined period of time. 
     Appendix 21 
     A communication system, comprising: 
     a first communication terminal; 
     a main communication terminal that can transmit first identification information and first associated information associated with the first communication terminal to a second communication terminal different from the first communication terminal; and 
     a second communication terminal that can receive the first identification information and the first associated information transmitted from the main communication terminal, 
     wherein the main communication terminal includes: 
     a communication unit, 
     a first storage unit that stores the first identification information corresponding to the first communication terminal, and the first associated information associated with the first identification information; 
     a second storage unit that stores second identification information corresponding to the second communication terminal, and second associated information associated with the second identification information; 
     a selection unit that selects information to be transmitted to the second communication terminal via the communication unit; 
     a reply request unit that causes the communication unit to transmit information for requesting a reply regarding whether transmission of a part or all of the first identification information and the first associated information is permitted, to the first communication terminal identified by way of the first identification information, in a case in which the information selected by the selection unit is a part or all of the first identification information and the first associated information; 
     a timing unit that measures a period of time since the communication unit transmitted the information for requesting a reply; 
     a first communication permission unit that permits the communication unit to transmit a part or all of the first identification information and the first associated information selected by the selection unit, in a case in which the communication unit receives a permission reply from the first communication terminal for permitting transmission of the part or all of the first identification information and the first associated information; and 
     a fourth communication permission unit that permits the communication unit to transmit a part or all of the first identification information and the first associated information to the second communication terminal, and permits the communication unit to transmit the part or all of the second identification information and the second associated information to the first communication terminal identified by way of the first identification information, in a case in which the period of time measured by the timing unit exceeds the predetermined period of time. 
     Appendix 22 
     A communication system, comprising: 
     a first communication terminal; 
     a main communication terminal that can transmit first identification information and first associated information associated with the first communication terminal to a second communication terminal different from the first communication terminal; and 
     a second communication terminal that can receive the first identification information and the first associated information transmitted from the main communication terminal, 
     wherein the main communication terminal includes: 
     a first communication unit that performs communication by way of a first communication method; 
     a second communication unit that performs communication by way of a second communication method different from the first communication method; 
     a first storage unit that stores the first identification information corresponding to the first communication terminal, and the first associated information associated with the first identification information; 
     a second storage unit that stores second identification information corresponding to the second communication terminal, and second associated information associated with the second identification information; 
     a selection unit that selects information to be transmitted to the second communication terminal via the first communication unit; 
     a reply request unit that causes the second communication unit to transmit information for requesting a reply regarding whether transmission of a part or all of the first identification information and the first associated information is permitted, to the first communication terminal identified by way of the first identification information, in a case in which the information selected by the selection unit is a part or all of the first identification information and the first associated information; 
     a timing unit that measures a period of time since the second communication unit transmitted the information for requesting a reply; 
     a first communication permission unit that permits the first communication unit to transmit a part or all of the first identification information and the first associated information selected by the selection unit, in a case in which the second communication unit receives a permission reply from the first communication terminal for permitting transmission of the part or all of the first identification information and the first associated information; and 
     a fourth communication permission unit that permits the first communication unit to transmit a part or all of the first identification information and the first associated information to the second communication terminal, and permits the second communication unit to transmit the part or all of the second identification information and the second associated information to the first communication terminal identified by way of the first identification information, in a case in which the period of time measured by the timing unit exceeds the predetermined period of time. 
     Appendix 23 
     A communication system, comprising: 
     a first communication terminal; 
     a main communication terminal that can transmit first identification information and first associated information associated with the first communication terminal to a second communication terminal different from the first communication terminal; and 
     a second communication terminal that can receive the first identification information and the first associated information transmitted from the main communication terminal, 
     wherein the main communication terminal includes: 
     a communication unit, 
     a first storage unit that stores the first identification information corresponding to the first communication terminal, and the first associated information associated with the first identification information; 
     a second storage unit that stores second identification information corresponding to the second communication terminal, and second associated information associated with the second identification information; 
     a selection unit that selects information to be transmitted to the second communication terminal via the communication unit; 
     a reply request unit that causes the communication unit to transmit information for requesting a reply regarding whether transmission of a part or all of the first identification information and the first associated information is permitted, to the first communication terminal identified by way of the first identification information, in a case in which the information selected by the selection unit is a part or all of the first identification information and the first associated information; 
     a timing unit that measures a period of time since the communication unit transmitted the information for requesting a reply; 
     a first communication permission unit that permits the communication unit to transmit a part or all of the first identification information and the first associated information selected by the selection unit, in a case in which the communication unit receives a permission reply from the first communication terminal for permitting transmission of the part or all of the first identification information and the first associated information; and 
     a fifth communication permission unit that permits the communication unit to transmit a part or all of the second identification information and the second associated information to the first communication terminal identified by way of the first identification information, in a case in which the period of time measured by the timing unit exceeds the predetermined period of time. 
     Appendix 24 
     A communication system, comprising: 
     a first communication terminal; 
     a main communication terminal that can transmit first identification information and first associated information associated with the first communication terminal to a second communication terminal different from the first communication terminal; and 
     a second communication terminal that can receive the first identification information and the first associated information transmitted from the main communication terminal, 
     wherein the main communication terminal includes: 
     a first communication unit that performs communication by way of a first communication method; 
     a second communication unit that performs communication by way of a second communication method different from the first communication method; 
     a first storage unit that stores the first identification information corresponding to the first communication terminal, and the first associated information associated with the first identification information; 
     a second storage unit that stores second identification information corresponding to the second communication terminal, and second associated information associated with the second identification information; 
     a selection unit that selects information to be transmitted to the second communication terminal via the first communication unit; 
     a reply request unit that causes the second communication unit to transmit information for requesting a reply regarding whether transmission of a part or all of the first identification information and the first associated information is permitted, to the first communication terminal identified by way of the first identification information, in a case in which the information selected by the selection unit is a part or all of the first identification information and the first associated information; 
     a timing unit that measures a period of time since the second communication unit transmitted the information for requesting a reply; 
     a first communication permission unit that permits the first communication unit to transmit a part or all of the first identification information and the first associated information selected by the selection unit, in a case in which the second communication unit receives a permission reply from the first communication terminal for permitting transmission of the part or all of the first identification information and the first associated information; and 
     a fifth communication permission unit that permits the second communication unit to transmit a part or all of the second identification information and the second associated information to the first communication terminal identified by way of the first identification information, in a case in which the period of time measured by the timing unit exceeds the predetermined period of time. 
     Appendix 25 
     The communication system according to appendix 22 or 24, 
     wherein the first communication terminal includes: 
     a display unit that can display predetermined information; 
     a first communication terminal side second communication unit that performs communication by way of the second communication method; 
     a third storage unit that stores a plurality of pieces of third identification information corresponding to a plurality of communication terminals, respectively, and a plurality of pieces of third associated information that are associated with the plurality of pieces of third identification information, respectively; 
     a comparing unit that compares a part or all of the second identification information and the second associated information with the third identification information and the third associated information stored in the third storage unit, in a case in which the first communication terminal side second communication unit receives the part or all of the second identification information and the second associated information; 
     an extracting unit that extracts a predetermined portion of the third identification information and the third associated information, which is determined by the comparing unit to include common contents with a part or all of the second identification information and the second associated information, from among the plurality of pieces of third identification information and the plurality of pieces of third associated information stored in the third storage unit; and 
     a display control unit that causes the display unit to display the predetermined portion of the third identification information and the third associated information extracted by the extracting unit. 
     Appendix 26 
     A communication system, comprising: 
     a first communication terminal that can transmit decryption key information; 
     a main communication terminal that can transmit encryption information encrypted from a part or all of first identification information and first associated information associated with the first communication terminal to a second communication terminal different from the first communication terminal; 
     the second communication terminal that can receive the encryption information transmitted from the main communication terminal; and 
     a server that can receive the decryption key information transmitted from the first communication terminal, and can transmit the decryption key information to the second communication terminal, 
     wherein the main communication terminal includes: 
     a first communication unit that performs communication by way of a first communication method; 
     a second communication unit that performs communication by way of a second communication method different from the first communication method; 
     a first storage unit that stores first identification information corresponding to the first communication terminal, and first associated information associated with the first identification information; 
     a second storage unit that stores second identification information corresponding to the second communication terminal, and second associated information associated with the second identification information; 
     a selection unit that selects information to be transmitted to the second communication terminal via the first communication unit; 
     an encryption processing unit that encrypts a part or all of the first identification information and the first associated information to generate encryption information, in a case in which the selection unit selects the part or all of the first identification information and the first associated information; 
     an encryption information transmission permission unit that permits the first communication unit to transmit the encryption information to the second communication terminal; and 
     a first notification information transmission unit that causes the second communication unit to transmit first notification information to the server, the first notification information including notification information for notifying of the fact that a part or all of the first identification information and the first associated information has been transmitted to the second communication terminal, the first identification information, and the second identification information, 
     wherein the server includes: 
     a server side second communication unit that can communicate by way of the second communication method; 
     a server side first storage unit that stores the first identification information and the second identification information included in the first notification information received by the server side second communication unit; 
     a server side decryption key information storage unit that can store the decryption key information transmitted from the first communication terminal; and 
     a second notification information transmission unit that causes the server side second communication unit to transmit second notification information, which includes notification information for notifying of the fact that a part or all of the first identification information and the first associated information has been transmitted from the main communication terminal to the second communication terminal, and the second identification information stored in the server side first storage unit, to the first communication terminal identified by way of the first identification information stored in the server side first storage unit, in a case in which the server side second communication unit receives the first notification information, 
     wherein the first communication terminal includes: 
     a first communication terminal side second communication unit that can communicate by way of the second communication method; and 
     a first communication terminal side first storage unit that stores the first identification information; 
     a first communication terminal side second storage unit that stores the second identification information included in the second notification information received by the first communication terminal side second communication unit; and 
     a first communication terminal side decryption key information storage unit that stores the decryption key information. 
     Appendix 27 
     The communication system according to appendix 26, 
     wherein the first communication terminal includes: 
     a first communication terminal side decryption key information transmission unit that causes the first communication terminal side second communication unit to transmit the decryption key information stored in the first communication terminal side decryption key information storage unit to the server, in a case in which the first communication terminal side second communication unit receives the second notification information, 
     wherein the second communication terminal includes: 
     a second communication terminal side first communication unit that performs communication by way of the first communication method; 
     a second communication terminal side second communication unit that performs communication by way of the second communication method different from the first communication method; 
     a second communication terminal side encryption information storage unit that stores the encryption information received by the second communication terminal side first communication unit; 
     a second communication terminal side decryption key information request unit that causes the second communication terminal side second communication unit to transmit first request information for requesting the decryption key information to the server; and 
     a decryption processing unit that decrypts the encryption information stored in the second communication terminal side encryption information storage unit, based on a decryption key included in the decryption key information transmitted from the server, and 
     wherein the server includes a server side decryption key information transmission unit that causes the server side second communication unit to transmit the decryption key information stored in the server side decryption key information storage unit to the second communication terminal identified by way of the second identification information stored in the server side first storage unit, in a case in which the server side second communication unit receives the first request information. 
     Appendix 28 
     The communication system according to appendix 27, 
     wherein the server includes: 
     a server side determination unit that determines whether the decryption key information is stored in the server side decryption key information storage unit, in a case in which the server side second communication unit receives the first request information; and 
     a server side decryption key information request unit that causes the server side second communication unit to transmit second request information for requesting transmission of the encryption information to the first communication terminal, in a case in which the server side determination unit determines that the encryption information is not stored in the server side decryption key information storage unit. 
     Appendix 29 
     The communication system according to appendix 28, 
     wherein the server includes a third notification information transmission unit that causes the server side second communication unit to transmit third notification information for notifying of the fact that the decryption key information is stored in the server side decryption key information storage unit, to the second communication terminal identified by way of the second identification information stored in the server side first storage unit, in a case in which the server side communication unit receives the decryption key information. 
     Appendix 30 
     The communication system according to appendix 28 or 29, 
     wherein the server includes a fourth notification information transmission unit that causes the server side second communication unit to transmit fourth notification information for notifying of the fact that the decryption key information is not stored in the server side decryption key information storage unit, to the second communication terminal identified by way of the second identification information stored in the server side first storage unit, in a case in which the server side determination unit determines that the decryption key information is not stored in the server side decryption key information storage unit.