Authentication system and authentication method

An authentication system for authenticating an operation direction directing remote operation of a remote controlled device connected to a communications network as transmitted by a remote control terminal which has been authorized, comprising:

• an operation data storage unit configured to store operation data including an operation item indicating a type of operation content of the remote operation and necessity of an authentication;
• an operation direction receiver configured to receive the operation direction from the remote control terminal;
• an authentication necessity decider configured to determine the necessity of the authentication based on the operation direction received by the operation direction receiver and the operation data;
• and
• an authenticator configured to authenticate the operation direction as transmitted by the remote control terminal which has been authorized when the authentication necessity decider determines that the authentication is necessary.