Distinguishing Live Faces from Flat Surfaces

One or more computer storage media having stored thereon multiple instructions that, when executed by one or more processors of a computing device, cause the one or more processors to:

• access multiple images including a face presented by a user;
• determine, based on the multiple images, whether motion is present in one or more components of the face;
• indicate that the user can be authenticated if motion is present in the one or more components of the face;
• and
• indicate that the user cannot be authenticated if motion is not present in the one or more components of the face.

One or more computer storage media having stored thereon multiple instructions that, when executed by one or more processors of a computing device, cause the one or more processors to:

• access multiple images including a face presented by a user;
• determine, based on the multiple images, whether the face included in the multiple images is a 3-dimensional structure or a flat surface by:
• accessing a first image and a second image of the multiple images,
• extracting one or more feature points from the first image and one or more feature points from the second image,
• matching feature points across the first image and the second image,
• using feature points matched across the first image and the second image to generate a homography matrix,
• generating a warped image by warping the first image using the homography matrix,
• determining an image difference between the warped image and the second image,
• identifying a first set of sub-regions in the first image,
• identifying a second set of sub-regions in the second image, and
• determining, based on a difference between color values of pixels in the first set of sub-regions and the second set of sub-regions, that the face included in the multiple images is a 3-dimensional structure if the difference between the color values of pixels in the first set of sub-regions and the second set of sub-regions meets a threshold value, and otherwise determining that the face included in the multiple images is a flat surface;
• and
• indicate that the user can be authenticated if the face included in the multiple images is a 3-dimensional structure;
• and
• indicate that the user cannot be authenticated if the face included in the multiple images is a flat surface.