Digital work protection system, recording medium apparatus, transmission apparatus, and playback apparatus

摘要

A server apparatus (200) encrypts content, based on a distribution key, and transmits the encrypted content to a PC (300) via a network (10). The PC (300), to which a memory card (400) is connected, outputs the received encrypted content to the memory card (400). The memory card (400) decrypts the encrypted content using the distribution key, converts the data format of the decrypted content, encrypts the content using a medium unique key that is unique to the memory card, and records the resulting re-encrypted content internally. A playback apparatus (500) decrypts the re-encrypted content using the medium unique key, and plays back the decrypted content.