PURPOSE: An authentication system is provided to improve security reliability by disabling the fabrication of an authentication result by external software manipulation. CONSTITUTION: A storage device(200) is connected with a host device(100) through a first interface(310) and stores content. An authentication device(300) is connected to a module composing the storage device and stores copy prevention information about the content. The copy prevention information includes an encoding key related to the encoding of the content. The storage device stores the content encoded by the encoding key. When the encoded content is provided to a host device, the authentication device decodes the encoded content. The copy prevention information includes DRM(Digital Right Management) rules about the content. [Reference numerals] (100) Host device; (110) Authentication device verification module; (200) Storage device; (240) First interface; (300) Authentication device; (302) Interface unit; (304) Authentication processing unit; (306) Storage unit; (310) Second interface
