A communication apparatus, a communication system, a communication apparatus control method and a recording medium for storing an implementation program thereof are disclosed. The communication apparatus includes a communication part providing a communicating party with an individual certificate with identification information thereof as via a first address and a common certificate without the identification information via a second address; a request execution part executing a process corresponding to a request received from the communicating party; and a denial part denying any process corresponding to requests other than a request to set the individual certificate in communication via the second address. According to the invention, it is possible to easily maintain a condition where authentication can be properly performed while maintaining security of communication.