Mobile terminal, mutual authentication system, method of controlling a mobile terminal and a mobile terminal control program

From a state where the security functions by operation of the user is temporarily disabled, the mobile terminal capable of improving convenience by automatically re enable security features in certain conditions, the mutual authentication system, control of the mobile terminal providing a control program of a method and a mobile terminal. Mobile phone 20 has a first state in which the effective operation of the user is to the operation key 24 when the mutual authentication is established between the authentication key 30, the user to the operation key 24 when the mutual authentication is not established a second state in which the operation becomes invalid, if the second state is a predetermined release operation, and a third state in which the operation of the operation key 24 is valid. If the mutual authentication is established in the third state, it shifts to the first state.