The utilization of various distributed contents is restricted by a simple method, its restriction can be released, and an accurate collection of fees for the contents is made possible. A client terminal 30 sends a request of contents (musical scores) and a key file to a server 10 via a communication line 20. In response to the request of these, a WEB server 11 transmits the contents stored in a database 13, and a key issuing server 12 transmits the key file. The WEB server 11 charges a fee when the key file is requested. A viewer 32 can only display the musical scores in the absence of the key file. With the use of the key file, however, the viewer 32 can print the musical scores as well. The key file is formed in accordance with a random value that is synchronized with the timing of an instruction for purchasing the contents.