Content on a storage medium is protected from unauthorized use, such as excessive copying or expired playback. A storage medium contains encrypted content and an encrypted content key with rules such as usage and copy rules. An interface between a record/playback device and the storage medium has enhanced security by not passing unprotected encryption keys that might be intercepted by external hackers. A content key is combined with usage and copy rules and then encrypted with a unique key, and may be doubly-encrypted with a control key before transmission over the interface. The unique key is generated from a key matrix on the record/playback device using row and columns received from the storage medium. The storage medium stores a pre-loaded copy of the unique key. The control key is generated from a random number on the record/playback device and storage medium avoiding transmission over the interface.