US 12,323,459 B2
Video replay attack detection
Björn Völcker, Lund (SE); and Stefan Lundberg, Lund (SE)
Assigned to AXIS AB, Lund (SE)
Filed by Axis AB, Lund (SE)
Filed on Sep. 30, 2022, as Appl. No. 17/957,775.
Claims priority of application No. 21201417 (EP), filed on Oct. 7, 2021.
Prior Publication US 2023/0114200 A1, Apr. 13, 2023
Int. Cl. H04L 9/40 (2022.01); G08B 13/196 (2006.01)
CPC H04L 63/1466 (2013.01) [G08B 13/19634 (2013.01); G08B 13/19667 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A method of detecting a video replay attack where a camera captures images of video played on a display screen instead of a live scene, the method comprising:
receiving image data at a first bit-depth, the image data having a first intensity range;
mapping the image data, using a mapping operation, from the first bit-depth to a second, reduced bit-depth, to produce a representation of the image data having a second intensity range;
generating metadata characterizing the mapping operation;
associating the metadata with the representation of the image data;
determining the first intensity range from the representation of the image data;
determining the second intensity range from the representation of the image data;
determining an expected mapping operation on basis of the second intensity range and the first intensity range;
comparing the mapping operation and the expected mapping operation; and
determining that the image data results from a video replay attack if a measure of the difference between the mapping operation and the expected mapping operation exceeds a threshold level.