A communication terminal device comprising: an assigning unit for generating a password for received data and assigning the generated password to the received data; a storage unit for storing the received data to which the password is assigned; an extracting unit for extracting information for identifying a notification destination of the received data; a notification unit for notifying the notification destination of the password, by using the information extracted by the extracting unit; and an output unit for outputting the received data to which the password is assigned responsive to input of the password, characterized in that: the storage unit further is adapted to store the notification destination of the received data and a password generation time at which the assigning unit generates the password for the received data; the notification unit is adapted to check, when new data is received, if the storage unit stores the received data whose notification destination is identical to a notification destination of the new data; when the notification unit determines that the storage unit stores the received data whose notification destination is identical to the notification destination of the new data, the notification unit obtains the password generation time of the received data stored in the storage unit, and checks if the password generation time of the received data stored in the storage unit is within a given period of time preceding reception of the new data, when the notification unit determines that the password generation time is within the period of time, the notification unit is adapted to assign the same password as that of the received data stored in the storage unit to the new data, and when the notification unit determines that the password generation time is not within the period of time, the assigning unit is adapted to generate a new password to the new data. an assigning unit for generating a password for received data and assigning the generated password to the received data; a storage unit for storing the received data to which the password is assigned; an extracting unit for extracting information for identifying a notification destination of the received data; a notification unit for notifying the notification destination of the password, by using the information extracted by the extracting unit; and an output unit for outputting the received data to which the password is assigned responsive to input of the password, characterized in that: the storage unit further is adapted to store the notification destination of the received data and a password generation time at which the assigning unit generates the password for the received data; the notification unit is adapted to check, when new data is received, if the storage unit stores the received data whose notification destination is identical to a notification destination of the new data; when the notification unit determines that the storage unit stores the received data whose notification destination is identical to the notification destination of the new data, the notification unit obtains the password generation time of the received data stored in the storage unit, and checks if the password generation time of the received data stored in the storage unit is within a given period of time preceding reception of the new data, when the notification unit determines that the password generation time is within the period of time, the notification unit is adapted to assign the same password as that of the received data stored in the storage unit to the new data, and when the notification unit determines that the password generation time is not within the period of time, the assigning unit is adapted to generate a new password to the new data. the storage unit further is adapted to store the notification destination of the received data and a password generation time at which the assigning unit generates the password for the received data; the notification unit is adapted to check, when new data is received, if the storage unit stores the received data whose notification destination is identical to a notification destination of the new data; when the notification unit determines that the storage unit stores the received data whose notification destination is identical to the notification destination of the new data, the notification unit obtains the password generation time of the received data stored in the storage unit, and checks if the password generation time of the received data stored in the storage unit is within a given period of time preceding reception of the new data, when the notification unit determines that the password generation time is within the period of time, the notification unit is adapted to assign the same password as that of the received data stored in the storage unit to the new data, and when the notification unit determines that the password generation time is not within the period of time, the assigning unit is adapted to generate a new password to the new data.