To prevent copyright infringement due to illegal copies of digital content by charging for use of copies of the digital content and to control copying by content purchasers beyond the scope of private use.

For encryption and decryption, encryption keys making a combination of encryption and decryption keys that are different are created in advance by a manager of the right of digital content as encryption and decryption keys for copying. To copy the digital content, a person who makes copies is caused to re-encrypt the content using the encryption key for copying. In this way, even the person who makes the copies is not allowed to use the copies unless he/she is given the decryption key for copying from the manager of the content. At the time when the decryption key for copying is delivered, the charge for using the copies is collected, whereby the charge for even the copies of the content is paid to the manager of the content.