When the recording mode of an information recording/playback device is a cognizant mode which analyzes embedded copy control information, the information recording/playback device performs content encryption using a content-encryption key generated by using a cognizant key as a content-encryption-key generating key in the cognizant mode. When the recording mode of the information recording/playback device is a non-cognizant mode which does not analyze the embedded copy control information, the information recording/playback device performs content encryption using a content-encryption key generated by using a cognizant key as a content-encryption-key generating key in the non-cognizant mode. By using these techniques, the above two recording modes are clearly distinguished and separately executed. This prevents an encryption mode indicator as copy control information and embedded copy control information from being mismatched.