Abstract: A data copyright management apparatus for handling data copyrights and data of digital cash, and for use in video conference systems is provided. The data copyright management apparatus is connected to a user terminal, and is used for performing decryption of encrypted digital data to be copied and edited, and also performing encryption of decrypted digital data to be stored, copied and transferred. The data copyright management apparatus may comprise one central processing unit so that either one of a microprosser of the user terminal and the microprocessor of the data copyright management apparatus performs decryption of the encrypted data and the other performs re-encryption of decrypted data at the same time. The data copyright management apparatus may also comprise two central processing units so that one central processing unit performs decryption of the encrypted data and the other central processing unit performs re-encryption of the decrypted data at the same time.

Abstract: A crypt key system for decrypting encrypted data for use, by a permit key including a decryption key, comprising a database/charging center, a broadcasting station, a receiving device and a communication device. The permit key is supplied to the broadcasting station in advance from the database/charging center. The permit key is broadcast from the broadcasting station. The receiving device receives the permit key via the broadcast. A request for use is executed to the database/charging center via the communication device. The database/charging center transmits the encrypted data via a communication line to the communication device and charges a fee. The communication device decrypts the encrypted data with the permit key received by the receiving device.

Abstract: A data copyright management system comprises a database for storing original data, a key control center for managing crypt keys, copyright management center for managing data copyrights, and a communication network for connecting these sections. Data supplied from the database to users is encrypted and distributed. The users decrypts the encrypted data by crypt keys obtained from the key control center or copyright management center. To supply data to users, there are the following two methods: a one-way supplying of encrypted data to users by means of broadcasting or the like; and two-way supplying of encrypted data to users corresponding to users' requests. A crypt key system used for encrypting data uses a secret-key cryptosystem, a public-key cryptosystem or a cryptosystem combining a secret-key and a public-key and further uses a copyright control program to control data copyrights.