The invention enables a provider and a retailer of digital contents to issue an electronic license to a consumer without wasting its own resources. A retailer sells digital contents to a consumer via the Internet. The retailer requests a license-issuing center to issue an electronic license corresponding to the digital contents and the user of the contents and receives the generated license. The user receives the license from the retailer via the Internet. The terminal used by the user certifies that he/she is a legitimate user using his/her license when he/she uses the digital contents provided from the provider. When the license is verified, the user can use the digital contents.