Patent ID: 7694333

Claim:
A communication apparatus that authenticates a communication partner by using a first digital certificate, the apparatus comprising: an authentication part configured to authenticate said communication partner by using a common certificate, said common certificate being a digital certificate that excludes identification information of an apparatus; an individualized certificate transmission part configured to acquire, in the case said authentication by said authentication part has been made successfully, an individualized certificate and transmit said individualized certificate to said communication partner, said individualized certificate being a digital certificate including identification information of said communication partner; the authentication part further configured to determine that a cause of an authentication failure includes an anomaly in the first digital certificate or a failure to store the first digital certificate in the communication partner, and determine that a cause of the authentication failure excludes a failure in a process of communicating with said communication partner or a failure in authentication processing; and a certificate request unit including a memory and configured to transmit a request for issue of said individualized certificate, and transmit a machine number, an Internet Protocol (IP) address, and a Media Access Control (MAC) address of said communication partner based on the determination of the authentication part, wherein said authentication part carries out said authentication when communicating with said communication partner first by using said first digital certificate including an individualized certificate, and said authentication part is further configured to carry out an authentication by using said common certificate when said authentication of said communication partner using said individualized certificate has failed.