A radio bus system, a radio communication apparatus and a registration
communication method which can ensure a minimum level of secrecy even
when radio is used during an authentication information registration
procedure. A hub station and each terminal comprises a mode switching
control circuit (10) for switching between two modes, one being a
registration mode to be used for the transmission and reception of
registration data, and the other being a normal mode to be used for the
transmission and reception of general data other than the registration
data, a scrambler (transmitter means) (22) for transmitting data after
providing the data with predetermined data processing corresponding to
the mode switched to, and a descrambler (receiver means) (27) for
performing on received data a predetermined restoration process
corresponding to the mode switched to. Restoration of the received data
is enabled only when the mode on the transmitting end and that on the
receiving end correspond with each other.