It is a form of digital rights management (DRM) developed by The 4C Entity, LLC (consisting of IBM, Intel, Matsushita and Toshiba).
The CPRM / CPPM specification defines a renewable cryptographic method for restricting content when recorded on physical media.
To accomplish these requirements, the system defined by the specification relies on public-key cryptography's key management for interchangeable media, content encryption, and "media-based renewability."
A controversial proposal to add generic key exchange commands (that could be utilized by CPRM and other content restriction technologies) to ATA specifications for removable hard drives was abandoned after outcry in 2001.
[2] CPRM is widely deployed in the popular Secure Digital card consumer-electronics flash memory format.