A method of authenticating a content provider and assuring content integrity by which the content provider is authenticated and the content integrity is assured upon download, exchange or transfer of a variety of multimedia contents through a wired/wireless communication network. The method of authenticating the content provider and assuring the content integrity, including downloading packaged contents with an electronic signature made thereto into a device of a user through a wired/wireless communication network, finding a URL address from which a certificate for verification of a signature of the content provider is provided, in a header of the contents, acquiring the certificate of the content provider after moving to the URL address, extracting a public key required for the verification of the electronic signature from the acquired certificate, and verifying the electronic signature by using the extracted public key.