A data conversion apparatus for receiving a key and data, and for performing data conversion for one of encryption and decryption of the data received using the key received, the data conversion apparatus comprising: a data scrambler adapted for performing data conversion; and a controller adapted for controlling a transfer signal indicating one of the key and the data to be transferred, wherein the controller is adapted to output the transfer signal in a case of transferring the one of the key and the data, and wherein the data scrambler includes, a sub converter adapted for performing the data conversion for the one of data encryption and data decryption by converting the data received using the key received, and for transferring at least one of the key received and the data received without data conversion upon receipt of the transfer signal outputted by the controller, wherein the sub converter includes at least one of, a data converter unit adapted for performing linear data conversion, and a data inverter unit adapted for performing a data conversion that is inverse to that of the data converter unit, characterized in that at least one of the data converter unit and the data inverter unit is adapted to perform the data conversion, and to receive the transfer signal outputted from the controller and to transfer at least one of the data and the key without data conversion according to the transfer signal received, when the controller outputs the transfer signal, wherein a) the controller is adapted to output a key transfer signal and a mask signal as the transfer signals for transferring the key received, and at least one of the data converter unit and the data inverter unit is adapted to transfer the key, upon receipt of the key transfer signal and the mask signal outputted from the controller, by nullifying the data received according to the key transfer signal received, and letting the key received pass through according to the mask signal received, or b) the controller is adapted to output a DATA TRANSFER signal that is a data transfer signal as the transfer signal for transferring the data received, and at least one of the data converter unit and the data inverter unit is adapted to transfer the data, upon receipt of the DATA TRANSFER signal outputted from the controller, by nullifying the key received and letting the data received pass through according to the DATA TRANSFER signal received. a data scrambler adapted for performing data conversion; and a controller adapted for controlling a transfer signal indicating one of the key and the data to be transferred, wherein the controller is adapted to output the transfer signal in a case of transferring the one of the key and the data, and wherein the data scrambler includes, a sub converter adapted for performing the data conversion for the one of data encryption and data decryption by converting the data received using the key received, and for transferring at least one of the key received and the data received without data conversion upon receipt of the transfer signal outputted by the controller, wherein the sub converter includes at least one of, a data converter unit adapted for performing linear data conversion, and a data inverter unit adapted for performing a data conversion that is inverse to that of the data converter unit, characterized in that at least one of the data converter unit and the data inverter unit is adapted to perform the data conversion, and to receive the transfer signal outputted from the controller and to transfer at least one of the data and the key without data conversion according to the transfer signal received, when the controller outputs the transfer signal, wherein a) the controller is adapted to output a key transfer signal and a mask signal as the transfer signals for transferring the key received, and at least one of the data converter unit and the data inverter unit is adapted to transfer the key, upon receipt of the key transfer signal and the mask signal outputted from the controller, by nullifying the data received according to the key transfer signal received, and letting the key received pass through according to the mask signal received, or b) the controller is adapted to output a DATA TRANSFER signal that is a data transfer signal as the transfer signal for transferring the data received, and at least one of the data converter unit and the data inverter unit is adapted to transfer the data, upon receipt of the DATA TRANSFER signal outputted from the controller, by nullifying the key received and letting the data received pass through according to the DATA TRANSFER signal received. a) the controller is adapted to output a key transfer signal and a mask signal as the transfer signals for transferring the key received, and at least one of the data converter unit and the data inverter unit is adapted to transfer the key, upon receipt of the key transfer signal and the mask signal outputted from the controller, by nullifying the data received according to the key transfer signal received, and letting the key received pass through according to the mask signal received, or b) the controller is adapted to output a DATA TRANSFER signal that is a data transfer signal as the transfer signal for transferring the data received, and at least one of the data converter unit and the data inverter unit is adapted to transfer the data, upon receipt of the DATA TRANSFER signal outputted from the controller, by nullifying the key received and letting the data received pass through according to the DATA TRANSFER signal received.