Content guard system for copy protection of recordable media

Abstract

A system and method for enabling broadcast programs to be copied once only by consumer recorders includes writing a unique media identification on each blank disk to which content is to copied in a read-only area of the disk before it is initially recorded. Also, a one-way key management media key block is written to the disk. A content key is derived by combining a media key, derived from the media key block, with the media identification. Additionally, to facilitate copying the content one time only, an exchange key is established between the recorder and a sender such as a satellite receiver or a disk player that is associated with the recorder, and the exchange key is modified with one or more special numbers representing control commands including copy once and copy no more. The modified exchange key is then encrypted using the content key to render an encrypted modified exchange key, and the encrypted modified exchange key is then hashed with a nonce to render a bus content key. The bus content key is then used to encrypt the data for copying the data to a disk. Unauthorized attempts to copy the data after the first authorized copy has been made cannot succeed because the media ID is different on subsequent blank media. Further, if illegal clones are manufactured that can calculate the media key, new blank media can change the media key block such that the clones can no longer calculate the correct media key. Authorized players, however, can decrypt the data to display it.