A communication apparatus connected to a wireless network for directly communicating with another terminal, said apparatus comprising: unicast-key generating means for generating a unicast key with a terminal (102,103) of a communication partner; and setting means for setting an encryption key for a communication with the terminal (102,103) of the communication partner, characterized in that said apparatus further comprises: determination means for determining if the communication apparatus and the terminal (102,103) of the communication partner can concurrently use different encryption keys in correspondence with a plurality of communication destinations, wherein said setting means are operable, when said determination means determines that at least one of the communication apparatus and the terminal of the communication partner cannot concurrently use different encryption keys in correspondence with the plurality of communication destinations, to set as the encryption key for the communication with the terminal of the communication partner an encryption key uniquely set in the wireless network for a communication in a terminal group that includes the communication apparatus and the terminal of the communication partner, and wherein said setting means are further operable, when said determination means determines that the communication apparatus and the terminal of the communication partner can concurrently use different encryption keys in correspondence with the plurality of communication destinations, to set the unicast key generated by said unicast-key generating means as the encryption key for the communication with the terminal of the communication partner. unicast-key generating means for generating a unicast key with a terminal (102,103) of a communication partner; and setting means for setting an encryption key for a communication with the terminal (102,103) of the communication partner, characterized in that said apparatus further comprises: determination means for determining if the communication apparatus and the terminal (102,103) of the communication partner can concurrently use different encryption keys in correspondence with a plurality of communication destinations, wherein said setting means are operable, when said determination means determines that at least one of the communication apparatus and the terminal of the communication partner cannot concurrently use different encryption keys in correspondence with the plurality of communication destinations, to set as the encryption key for the communication with the terminal of the communication partner an encryption key uniquely set in the wireless network for a communication in a terminal group that includes the communication apparatus and the terminal of the communication partner, and wherein said setting means are further operable, when said determination means determines that the communication apparatus and the terminal of the communication partner can concurrently use different encryption keys in correspondence with the plurality of communication destinations, to set the unicast key generated by said unicast-key generating means as the encryption key for the communication with the terminal of the communication partner. determination means for determining if the communication apparatus and the terminal (102,103) of the communication partner can concurrently use different encryption keys in correspondence with a plurality of communication destinations, wherein said setting means are operable, when said determination means determines that at least one of the communication apparatus and the terminal of the communication partner cannot concurrently use different encryption keys in correspondence with the plurality of communication destinations, to set as the encryption key for the communication with the terminal of the communication partner an encryption key uniquely set in the wireless network for a communication in a terminal group that includes the communication apparatus and the terminal of the communication partner, and wherein said setting means are further operable, when said determination means determines that the communication apparatus and the terminal of the communication partner can concurrently use different encryption keys in correspondence with the plurality of communication destinations, to set the unicast key generated by said unicast-key generating means as the encryption key for the communication with the terminal of the communication partner.