In an authentication system, a mobile communication client transmits to an authentication server a bit signal that includes an image capture bit sequence obtained by capturing an image of a self-aware two-dimensional code having authentication information embedded in a correction area, and a number bit sequence that indicates a serial number of an authentication application program being stored in storage. The authentication server authenticates the user of the mobile communication client and the self-aware two-dimensional code. Subsequently, the authentication server transmits designated information expressed by the self-aware two-dimensional code to the mobile communication client, on the condition that the user and the self-aware two-dimensional code are successfully authenticated. Consequently, the mobile communication client is able to acquire the designated information expressed by the self-aware two-dimensional code.