Abstract: Systems and techniques for user authentication are described. A portable electronic device can include an imaging sensor and a motion sensor. Multiple images of a face of a user can be acquired by using an imaging sensor. Motion information can be obtained by using a motion sensor. Next, a first motion vector can be determined based on the multiple images, and a second motion vector can be determined based on the motion information. The user can then be authenticated based on (1) determining a similarity measure between the first motion vector and the second motion vector, and (2) performing facial recognition on at least one of the multiple images. Note that the similarity measure can be used to detect a virtual-camera attack. Specifically, authentication can fail if the similarity measure is less than a threshold.

Abstract: Systems and techniques for user authentication are described. A portable electronic device can include an imaging sensor and a motion sensor. Multiple images of a face of a user can be acquired by using an imaging sensor. Motion information can be obtained by using a motion sensor. Next, a first motion vector can be determined based on the multiple images, and a second motion vector can be determined based on the motion information. The user can then be authenticated based on (1) determining a similarity measure between the first motion vector and the second motion vector, and (2) performing facial recognition on at least one of the multiple images. Note that the similarity measure can be used to detect a virtual-camera attack. Specifically, authentication can fail if the similarity measure is less than a threshold.

Abstract: During a technique for authenticating a user using a portable electronic device (such as a smartphone) while preventing successful 2D media attacks and virtual-camera attacks, the portable electronic device provides an instruction to a user to move the portable electronic device relative to the user's face. Then, using an imaging sensor in the portable electronic device, the portable electronic device acquires, a series of images while the portable electronic device is at different positions or orientations relative to the user's face, where the series of images include at least two images relative to a symmetry axis of the user's face (such as the midline). Moreover, the portable electronic device determines a change in a sign of a nose angle in at least the two images. Next, the portable electronic device authenticates the user based on at least one of the series of images using a facial-recognition technique.

Abstract: During a technique for authenticating a user using a portable electronic device (such as a smartphone) while preventing successful 2D media attacks and virtual-camera attacks, the portable electronic device provides an instruction to a user to move the portable electronic device relative to the user's face. Then, using an imaging sensor in the portable electronic device, the portable electronic device acquires, a series of images while the portable electronic device is at different positions or orientations relative to the user's face, where the series of images include at least two images relative to a symmetry axis of the user's face (such as the midline). Moreover, the portable electronic device determines a change in a sign of a nose angle in at least the two images. Next, the portable electronic device authenticates the user based on at least one of the series of images using a facial-recognition technique.