Content Protection for Removable Media (CPRM) is a hardware-based technology designed to enforce copy protection restrictions through built-in mechanisms in storage media that would prevent unauthorized file copying.
Based on a technology called broadcast encryption that was developed by Amos Fiat and Moni Naar in 1993, the CPRM system would be used to incorporate digital tags into storage media, such as recordable CDs (CD-R, CD-RW) and flash memory cards for MP3 players.
CPRM was developed by 4C Entity, an industry consortium originally made up of Intel, IBM, Matsushita, and Toshiba. The system has been highly controversial, because it could be used not only with removable media, but as a part of every new hard drive produced as well. Technical Committee T13 (a coalition of companies that produce both flash memory and hard drives) considered adopting CPRM as an industry standard, but has since given approval to an alternative plan in development at Phoenix Technologies that would be used for other purposes - such as security mechanisms on removable media - in addition to copy protection.