A base-unit-side radio communication apparatus that is configured to perform communication with a handset-side radio communication apparatus (2, 3), the base-unit-side radio communication apparatus comprising: a radio communication section that is configured to establish a radio link and transmit and receive control data and speech data for a telephone call; and a limited-rewritable information storage section that is configured to store an encryption key and in which the number of rewritable times is limited, wherein: when receiving an encrypted-communication activation request including information indicating an encryption key from the handset-side radio communication apparatus after establishing a radio link with the handset-side radio communication apparatus, the radio communication section is configured to activate encrypted communication with the handset-side radio communication apparatus in case the encryption key stored in the limited-rewritable information storage section corresponds to the received information indicating the encryption key; when receiving a position registration request, said position request playing the role of an access rights procedure request, not encrypted using the encryption key transmitted from the handset-side radio communication apparatus, the radio communication section is configured to transmit a further signal to request generation of a new common encryption key and a signal of accept for the position registration request to the handset-side radio communication apparatus, using an unencrypted signal in case the received signal is not encrypted. a radio communication section that is configured to establish a radio link and transmit and receive control data and speech data for a telephone call; and a limited-rewritable information storage section that is configured to store an encryption key and in which the number of rewritable times is limited, wherein: when receiving an encrypted-communication activation request including information indicating an encryption key from the handset-side radio communication apparatus after establishing a radio link with the handset-side radio communication apparatus, the radio communication section is configured to activate encrypted communication with the handset-side radio communication apparatus in case the encryption key stored in the limited-rewritable information storage section corresponds to the received information indicating the encryption key; when receiving a position registration request, said position request playing the role of an access rights procedure request, not encrypted using the encryption key transmitted from the handset-side radio communication apparatus, the radio communication section is configured to transmit a further signal to request generation of a new common encryption key and a signal of accept for the position registration request to the handset-side radio communication apparatus, using an unencrypted signal in case the received signal is not encrypted. when receiving an encrypted-communication activation request including information indicating an encryption key from the handset-side radio communication apparatus after establishing a radio link with the handset-side radio communication apparatus, the radio communication section is configured to activate encrypted communication with the handset-side radio communication apparatus in case the encryption key stored in the limited-rewritable information storage section corresponds to the received information indicating the encryption key; when receiving a position registration request, said position request playing the role of an access rights procedure request, not encrypted using the encryption key transmitted from the handset-side radio communication apparatus, the radio communication section is configured to transmit a further signal to request generation of a new common encryption key and a signal of accept for the position registration request to the handset-side radio communication apparatus, using an unencrypted signal in case the received signal is not encrypted.