In the present invention, copyrights of digital data in a database system including real time transmission of a digital picture are controlled. Permit keys including a crypt key, are used when data which is encrypted and supplied is displayed, edited, stored, copied and transferred. As necessary, one or more of a copyright control program, copyright information or copyright control message are used, in addition to the permit key. The copyright control program, the copyright information and the copyright control message are supplied together with the permit key, or together with the data, or a part of them is supplied together with the permit key and the other part of them is supplied together with the data. The permit key, the copyright control message, the copyright information and the copyright control program are supplied with encryption or without encryption. The data is transmitted with encryption and is decrypted to be used, and may be encrypted again when stored, copied or transferred.