A high-density optical disc, a method for encrypting data and recording the encrypted data thereon, and a method for reproducing the encrypted data recorded thereon. A high-density optical disc such as a Blu-ray disc-read only memory (BD-ROM) has a helical track formed from the disc's outer periphery to the disc's inner periphery. An order of recording data frames on the BD-ROM is diametrically opposite to that of a rewritable optical disc such as a Blu-ray disc rewritable (BD-RE). Data can be encrypted using disc radius information or an address unit (AU) number contained in an AU and then the encrypted data is recorded on the high-density optical disc. Thus, a user holding the optical disc apparatus such as the BD-RE player can be prevented from unlawfully copying data of the BD-ROM to the BD-RE and unlawfully reproducing the copied data.