A technology of detecting an act of spoofing in a security system (face authentication system) using face authentication is widely known. The act of spoofing is an act of pretending to be another person to fraudulently utilize a system. The act of spoofing is hereinafter also simply referred to as spoofing.
Spoofing against a face authentication system is performed by an impersonator presenting another person's face different from that of the impersonator to a camera for face imaging. The method of presenting another person's face includes a method of presenting a photograph of another person's face to a camera in the system. Further, the method includes a method of presenting a video image of another person's face displayed on a display of a smartphone or the like to a camera in the system. Examples of related arts relating to such spoofing are described in PTLs 1 to 8 below.
For example, a related art described in PTL 1 detects a line-of-sight of a user from an image captured from a camera, while presenting an image for drawing the user's attention on a display device. Then, the related art (liveness detection) determines that the user is a living body when the line-of-sight of the user points in a direction of the display device, otherwise determines that spoofing exists.
Further, a related art described in PTL 2 acquires a plurality of facial images of a user respectively captured from a plurality of different lines of sight. Then, the related art extracts feature points in the user's face from the respective plurality of facial images and determines whether or not the feature points are on a same plane. Then, the related art determines whether or not spoofing exists, in accordance with whether or not the feature points are on a same plane.
Further, a related art described in PTL 3 measures distances and angles to a plurality of measured points in a user's face by a distance sensor to specify positions of the plurality of measured points. Then, the related art determines whether or not spoofing exists, in accordance with whether or not the plurality of measured points are on a same plane.
Further, a related art described in PTL 4 guides a user to move a line-of-sight by randomly moving a mark displayed on a display device. Then, the related art determines whether or not spoofing exists, in accordance with whether or not the line-of-sight movement of the user agrees with a track of the mark.
Further, a related art described in PTL 5 causes a user to move his or her face in a direction instructed on a display screen and captures the movement with a camera. Then, the related art determines whether or not spoofing exists, in accordance with whether or not a movement of a feature point can be detected in time-series images capturing the user.
Further, a related art described in PTL 6 instructs a user on a way to move a predetermined part of his or her face (e.g. opening and closing of an eye) and captures the user's face. Then, the related art determines whether or not spoofing exists, in accordance with whether or not the predetermined part of the face in an obtained dynamic image changes in accordance with the instruction.
Further, a related art described in PTL 7 captures a line-of-sight movement of a user moving in a presented image as a dynamic line-of-sight pattern including time-series data of a moving speed and a moved position. Then, the related art registers the movement associated with a user identifier. Then, the related art checks the user's dynamic line-of-sight pattern being an authentication target against a registered dynamic line-of-sight pattern to evaluate a degree of matching. By use of the related art, whether or not spoofing exists can be determined in accordance with the degree of matching of the dynamic line-of-sight patterns.
Further, PTL 8 describes a line-of-sight detection technology that can be employed in the respective related arts described in PTLs 1, 4, and 7. The technology specifies a pupil included in a facial image and detects a line-of-sight from a position of the pupil and a direction of the face.
Thus, as a spoofing detection technology, a method of determination by whether or not a line-of-sight points in a direction of a display device is proposed. A method of determination by whether or not a subject of imaging is a three-dimensional object, and a method of determination by whether or not a line-of-sight and a movement of a face, as instructed or as registered, can be detected, are also proposed.