Spoof detection using illumination sequence randomization
Technology described herein includes a method that includes obtaining a set of color-coded sequences, each of which includes a sequence of colors. Each color-coded sequence has auto-correlation properties characterized by a merit factor larger than a first predetermined threshold, and cross-correlation properties among the color-coded sequences characterized by a demerit factor lower than a second predetermined threshold. A color-coded sequence is randomly selected from the set of color-coded sequences. A subject is illuminated in accordance with the sequence of colors in the selected color-coded sequence. A sequence of images of the subject are captured, and are temporally synchronized with illumination by the color-coded sequence. A filtered response image is generated from the sequence of images by a matched filtering process. Based on the filtered response image, it is determined that the subject is an alternative representation of a live person. In response, access to a secure system is prevented.
1. A computer-implemented method comprising:
obtaining a set of multiple color-coded sequences;
randomly selecting a color-coded sequence from the set of multiple color-coded sequences, the color-coded sequence associated with a matched filter in a matched filtering process;
illuminating a subject in accordance with a sequence of colors in the color-coded sequence;
capturing a sequence of images of the subject, wherein the sequence of images is temporally synchronized with illumination by the color-coded sequence;
generating, by the matched filtering process using the matched filter associated with the color-coded sequence, a filtered response image from the sequence of images of the subject; and
determining, based on the filtered response image, that the subject is a live person.
2. The method of claim 1 , wherein determining, based on the filtered response image, that the subject is the live person comprises processing the filtered response image using a machine learning process trained to discriminate between filtered response images of live persons and filtered response images of alternative representations of the live persons.
3. The method of claim 2 , wherein the alternative representations of the live persons comprise a previously captured photograph of the live person printed on paper, or an image presented on a display device.
4. The method of claim 2 , wherein the alternative representations of the live persons comprise video replay of the live person on a display device.
5. The method of claim 1 , wherein the filtered response image from the sequence of images of the subject comprises:
generating, from the sequence of images, a sequence of spatially aligned images;
calculating a sequence of filtered response images by applying the matched filter to the sequence of spatially aligned images; and
selecting the filtered response image from the sequence of filtered response images.
6. The method of claim 1 , further comprising:
responsive to determining that the subject is the live person, initiating an authentication process for determining if the live person is authorized to access a secure system.
7. The method of claim 1 , further comprising:
randomly selecting a second color-coded sequence from the set of multiple color-coded sequences;
illuminating a second subject in accordance with the sequence of colors in the second color-coded sequence;
capturing a second sequence of images of the second subject, wherein the second sequence of images are temporally synchronized with illumination by the second color-coded sequence;
generating, by a matched filtering process using the second color-coded sequence, a second filtered response image from the second sequence of images of the second subject; and
determining, based on the second filtered response image, that the second subject is an alternative representation of a live person.
8. The method of claim 7 , further comprising:
responsive to determining that the second subject is the alternative representation of the live person, preventing access to a secure system.
9. A computer-implemented system, comprising:
one or more computers; and
one or more computer memory devices interoperably coupled with the one or more computers and having tangible, non-transitory, machine-readable media storing one or more instructions that, when executed by the one or more computers, perform operations comprising:
obtaining a set of multiple color-coded sequences;
randomly selecting a color-coded sequence from the set of multiple color-coded sequences, the color-coded sequence associated with a matched filter in a matched filtering process;
illuminating a subject in accordance with a sequence of colors in the color-coded sequence;
capturing a sequence of images of the subject, wherein the sequence of images is temporally synchronized with illumination by the color-coded sequence;
generating, by the matched filtering process using the matched filter associated with the color-coded sequence, a filtered response image from the sequence of images of the subject; and
determining, based on the filtered response image, that the subject is a live person.
10. The computer-implemented system of claim 9 , wherein determining, based on the filtered response image, that the subject is the live person comprises processing the filtered response image using a machine learning process trained to discriminate between filtered response images of live persons and filtered response images of alternative representations of the live persons.
11. The computer-implemented system of claim 10 , wherein the alternative representations of the live persons comprise a previously captured photograph of the live person printed on paper, or an image presented on a display device.
12. The computer-implemented system of claim 10 , wherein the alternative representations of the live persons comprise video replay of the live person on a display device.
13. The computer-implemented system of claim 9 , wherein the filtered response image from the sequence of images of the subject comprises:
generating, from the sequence of images, a sequence of spatially aligned images;
calculating a sequence of filtered response images by applying a matched filter to the sequence of spatially aligned images; and
selecting the filtered response image from the sequence of filtered response images.
14. The computer-implemented system of claim 9 , the operations further comprise:
responsive to determining that the subject is the live person, initiating an authentication process for determining if the live person is authorized to access a secure system.
15. The computer-implemented system of claim 9 , the operations further comprise:
randomly selecting a second color-coded sequence from the set of multiple color-coded sequences;
illuminating a second subject in accordance with the sequence of colors in the second color-coded sequence;
capturing a second sequence of images of the second subject, wherein the second sequence of images are temporally synchronized with illumination by the second color-coded sequence;
generating, by a matched filtering process using the second color-coded sequence, a second filtered response image from the second sequence of images of the second subject; and
determining, based on the second filtered response image, that the second subject is an alternative representation of a live person.
16. The computer-implemented system of claim 15 , the operations further comprise:
responsive to determining that the second subject is the alternative representation of the live person, preventing access to a secure system.
17. A non-transitory, computer-readable medium storing one or more instructions executable by a computer system to perform operations comprising:
obtaining a set of multiple color-coded sequences;
randomly selecting a color-coded sequence from the set of multiple color-coded sequences, the color-coded sequence associated with a matched filter in a matched filtering process;
illuminating a subject in accordance with a sequence of colors in the color-coded sequence;
capturing a sequence of images of the subject, wherein the sequence of images is temporally synchronized with illumination by the color-coded sequence;
generating, by the matched filtering process using the matched filter associated with the color-coded sequence, a filtered response image from the sequence of images of the subject; and
determining, based on the filtered response image, that the subject is a live person.
18. The non-transitory, computer-readable medium of claim 17 , wherein determining, based on the filtered response image, that the subject is the live person comprises processing the filtered response image using a machine learning process trained to discriminate between filtered response images of live persons and filtered response images of alternative representations of the live persons.
19. The non-transitory, computer-readable medium of claim 17 , wherein the filtered response image from the sequence of images of the subject comprises:
generating, from the sequence of images, a sequence of spatially aligned images;
calculating a sequence of filtered response images by applying a matched filter to the sequence of spatially aligned images; and
selecting the filtered response image from the sequence of filtered response images.
20. The non-transitory, computer-readable medium of claim 17 , the operations further comprise:
responsive to determining that the subject is the live person, initiating an authentication process for determining if the live person is authorized to access a secure system.