Patent ID: 6889327

Claim:
A copyrighted digital data management method for a network system in which first and second user terminals are connected to a contents provider via a network and are connected to each other via the network or a leased line, the method comprising the steps of: transmitting a request for using copyrighted digital data from said first user terminal to said contents provider; executing a data usage accounting procedure between said first user terminal and said contents provider; transmitting enciphered copyrighted digital data generated by enciphering the copyrighted digital data using encryption key data, decryption key data for deciphering the enciphered copyrighted digital data, digital sample preview data which is generated from an outline of the copyrighted digital data at a non-chargeable level without enciphering and is reproducible without the decryption key data, and additional data required for accounting from said contents provider to said first user terminal; receiving those data by said first user terminal and recording those data on a data recording medium, therein; and transmitting the enciphered copyrighted digital data, the digital sample preview data, and the additional data without transmitting the decryption key data from said first user terminal to said second user terminal.