Data coypright management method

A data copyright management method used for producing new data by editing original data, the method comprising the steps of:

• a database supplies a plurality of original data encrypted respectively by using each first secret-key thereof, to a primary user;
• said primary user makes a request for use to a copyright management center by presenting a public-key of said primary user;
• said copyright management center sends said first secret-key of each of said original data and a second secret-key of each said original data to said primary user;
• said primary user decrypts said plurality of original data encrypted, by using said first secret-key of each said original data;
• said primary user produces new data which is produced from a plurality of edited data by editing said plurality of original data using an edit program;
• said primary user encrypts said plurality of edited data respectively by said second secret-key of each said original data and performs a digital signature on editing process data of said edit program by using a private-key of said primary user, and supplies both said plurality of edited data and said editing process data with said digital signature to a secondary user;
• said secondary user requests use of said new data by presenting said editing process data with said digital signature to said copyright management center;
• said copyright management center confirms an editor as said primary user from said digital signature using said public-key of said primary user, and provides said secondary user with said second secret-key of each said original data;
• and
• said secondary user decrypts said plurality of edited data which have been encrypted, respectively by using said second secret-key of each said original data, and obtains said new data using said edit program and said editing process data.