Copyrighted digital data management method and system

摘要

After a user terminal (200) executes a data usage accounting procedure for a contents provider (100), enciphered copyrighted digital data (K(D)) generated by enciphering chargeable copyrighted digital data (D) using encryption key data (K), digital sample preview data (S(D)) generated from an outline of the copyrighted digital data at a non-chargeable level without enciphering, decryption key data (Kd) for deciphering the enciphered copyrighted digital data, and additional data (AD) required for accounting are transmitted from the contents provider (100) to the user terminal (200) over a network.