A communication apparatus has a communication part and authenticates a communication partner by using a digital certificate, wherein the communication apparatus includes an authentication part carrying out authentication of the communication partner by using a common certificate, the common certificate being a digital certificate not including identification information of an apparatus, and an individualized certificate transmission part acquiring, in the case the authentication by the authentication part has been made successfully, individualized certificate and transmitting the individualized certificate to said communication partner, the individualized certificate being a digital certificate including identification information of the communication partner.
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