The level of the spectrally spread anti-duplication control signal to be superimposed on an information signal such as a video signal is changed by using a random number RD generated by a random number generation unit 163. Since it is difficult to follow after the change of the level of the spectrally spread anti-duplication control signal, elimination of the anti-duplication control signal from the information signal is made further difficult. This can reliably provide the anti-duplication control signal to the receiving side.