Abstract
The amount of digital content grows exponentially by the development of the internet and the change of computing environments and the target also is getting wider. The industry using this digital content has been growing greatly. However, the distribution of pirated digital content is increasing using internet because digital content is easy to store and transmit and the damage is growing. In this paper, we propose safety trading system which can conceal the author's information safely in digital content in order to block illegal distribution of digital content. ARIA encryption algorithm is used to protect the concealed information of author in digital content and it is a help to track the illegal traders by doing fingerprinting of buyer information to digital content and managing the transaction information. The technical support for copyright dispute is to allow by providing the capability to verify illegal edit to original digital contents.