The present invention provides a method for controlling copyrights of digital data in a database system including real time transmission of a digital picture. Copyrights are controlled using one or more of the following, as necessary, in addition to a permit key: a copyright control program, copyright information or copyright control message. The copyright control program, the copyright information and the copyright control message are supplied together with the permit key, or they are supplied together with the data. Otherwise, a part of them is supplied together with the permit key and the other part of them is supplied together with the data. The data, the permit key, the copyright control message, the copyright information and the copyright control program are (1) transmitted while encrypted, but are decrypted when used, or (2) they are transmitted while encrypted and decrypted for display only, otherwise remaining encrypted, or (3) they may not be encrypted at all.