Recording apparatus recording medium, playback apparatus, recording method and playback method

The present invention provides a recording method and a recording apparatus whereby digital data is recorded onto a disc as run-length limited code used for modulating marks or spaces on the disc and, at the same time, the recorded digital data is encrypted by using key data which is also recorded onto the same disc by variation of the shape of marks or spaces with timing having no effect on the edges of the marks or the spaces. The present invention also provides a playback method and a playback apparatus for reproducing the digital data and the key data recorded on the disc by the recording method and/or the recording apparatus from the disc with the key data used for decrypting the reproduced digital data.