A mobile device comprising: a display; a camera; a motion sensor; one or more processors; and a memory storing one or more programs including instructions which, when executed by the one or more processors, cause the one or more processors to: detect, via the motion sensor, if the mobile device is lifted, while the mobile device is in a locked state; in response to detecting that the mobile device is lifted while the mobile device is in the locked state: activate the display; obtain an image from the camera; display the obtained image on the display; detect a face included in the obtained image; and perform an authentication of a user based on the face being detected in the obtained image by determining the detected face as an already registered face; based on performing the authentication of the user, control the display to superimpose on the obtained image a message indicating that the identity of the user is being checked; and based on a result of the authentication being successful, switch a state of the mobile device from the locked state to an unlocked state. a display; a camera; a motion sensor; one or more processors; and a memory storing one or more programs including instructions which, when executed by the one or more processors, cause the one or more processors to: detect, via the motion sensor, if the mobile device is lifted, while the mobile device is in a locked state; in response to detecting that the mobile device is lifted while the mobile device is in the locked state: activate the display; obtain an image from the camera; display the obtained image on the display; detect a face included in the obtained image; and perform an authentication of a user based on the face being detected in the obtained image by determining the detected face as an already registered face; based on performing the authentication of the user, control the display to superimpose on the obtained image a message indicating that the identity of the user is being checked; and based on a result of the authentication being successful, switch a state of the mobile device from the locked state to an unlocked state. detect, via the motion sensor, if the mobile device is lifted, while the mobile device is in a locked state; in response to detecting that the mobile device is lifted while the mobile device is in the locked state: activate the display; obtain an image from the camera; display the obtained image on the display; detect a face included in the obtained image; and perform an authentication of a user based on the face being detected in the obtained image by determining the detected face as an already registered face; based on performing the authentication of the user, control the display to superimpose on the obtained image a message indicating that the identity of the user is being checked; and activate the display; obtain an image from the camera; display the obtained image on the display; detect a face included in the obtained image; and perform an authentication of a user based on the face being detected in the obtained image by determining the detected face as an already registered face; based on performing the authentication of the user, control the display to superimpose on the obtained image a message indicating that the identity of the user is being checked; and based on a result of the authentication being successful, switch a state of the mobile device from the locked state to an unlocked state.