Method and system for authentication

An authentication service system performing user authentication by using a short message service (SMS), comprising:

• an authentication service component;
• and
• a verification component,
• wherein the authentication service component transfers use information received as basic authentication information to the verification component, confirms an IP address which is access information of a mobile device accessed for the user authentication, and transfers the confirmed IP address of the mobile device and an SMS authentication value input from the mobile device to the verification component, and
• the verification component generates the SMS authentication value to be used for authenticating the corresponding user to correspond to the transferred user information and transmits the generated SMS authentication value to a registered mobile device corresponding to the corresponding user information, confirms the IP address which a communication company allocates to the registered mobile device, and verifying whether the user authentication is appropriate according to whether the SMS authentication value transferred from the authentication service component and the generated SMS authentication value coincide with each other and whether the IP address transferred from the authentication service component and the confirmed IP address allocated by the communication company coincide with each other.