I found this from http://www.theregister.co.uk/2001/0...ou_ever_wanted/
don't know if this is what you mentioned?

1. What is CPRM?

CPRM or Content Protection for Recordable Media is a mechanism for controlling the copying, moving and deletion of digital media on a host device, such as a personal computer, or other digital player. It's already used in specific removable media, and is now being proposed for inclusion in the ATA specification, for hard drives.

Each CPRM-compatible ATA hard drive is individually signed, and authenticates the playback and movement of files on the device against a central server using CPRM-compliant software.