Content Protection for Recordable Media and Pre-Recorded Media (CPRM / CPPM) is a mechanism for controlling the copying, moving, and deletion of digital media on a host device, such as a personal computer, or other player. It is a form of

digital rights management Digital rights management (DRM) is the management of legal access to digital content. Various tools or technological protection measures (TPM) such as access control technologies can restrict the use of proprietary hardware and copyrighted works. ...

(DRM) developed by The

4C Entity The 4C Entity is a digital rights management (DRM) consortium formed by IBM, Intel, Panasonic and Toshiba that has established and licensed interoperable cryptographic protection mechanisms for removable media technologies. 4C Entity was founded i ...

, LLC (consisting of IBM, Intel, Matsushita and Toshiba). The CPRM / CPPM specification defines a renewable

cryptographic Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or '' -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adve ...

method for restricting content when recorded on physical media. The currently implemented method utilizes the

Cryptomeria cipher The Cryptomeria cipher, also called C2, is a proprietary block cipher defined and licensed by the 4C Entity. It is the successor to CSS algorithm (used for DVD-Video) and was designed for the CPRM/CPPM digital rights management scheme which are ...

(C2) algorithm for symmetric encryption. The types of physical media supported include, but are not limited to, recordable DVD media and

flash memory Flash memory is an electronic non-volatile computer memory storage medium that can be electrically erased and reprogrammed. The two main types of flash memory, NOR flash and NAND flash, are named for the NOR and NAND logic gates. Both us ...

. The most widespread use of CPRM is arguably in Secure Digital cards such as the SD-Audio standard. Note that the available 0.9 revision includes only the portions of the specification covering DVD media. The CPRM / CPPM specification was designed to meet the requirements of intellectual property owners while balancing the implementation requirements of manufacturers. 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." The use of the CPRM specification and access to the cryptographic materials required to implement it requires a license from

, LLC. The license includes a facsimile key for the product which uses CPRM / CPPM technology. 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. CPRM is widely deployed in the popular Secure Digital card consumer-electronics flash memory format.{{cn, date=July 2021

Notes and references

External links

2001 The Register article on CPRM in ATA drives
Digital rights management standards Compact Disc and DVD copy protection