Detection of Contact-Lens-Based Iris Biometric Spoofs Using Stereo Imaging

Abstract

Cosmetic contact lenses can be used to spoof an iris biometric system, either to evade being matched to a watch list or in principle even to masquerade as a selected other person. Existing approaches to detecting whether or not a person is wearing cosmetic contact lenses either are limited to detecting lenses created by a particular manufacturing technology, assume knowledge of the particular pattern printed in/on the lens, or require a sequence of images. We present proof-of-concept results for a method of detecting cosmetic contact lenses that is general, in the sense that it assumes nothing about the manufacturing technique or texture pattern of the lens, and that requires only a "snapshot" instance of imaging. The "snapshot" is a stereo pair of images, from which the shape of the surface of the iris texture region is estimated. In the absence of contacts or the presence of clear contacts, the iris region presents a coarse planar surface. In the presence of cosmetic contacts, the iris region presents a convex surface. Thus the problem of determining if a person is wearing a cosmetic contact lens is transformed into the problem of classifying the estimated surface shape for the iris region. This is the first approach to analyze iris biometric images in the context of 3D shape.

Contact lens detection in iris images

“…The presence of cosmetic contact lenses is quite easy to reveal by manual visual inspection especially if the lens is not properly inserted or if the pure lens and original iris texture are otherwise separately observed [32]. However, detection of well-aligned cosmetic lenses of some printing patterns can be difficult using only the human eye.…”

“…However, soft contact lenses can be designed to maintain a specific orientation after eye blinking or any other movement by making it to be heavier at the bottom [5]. In theory, there exist no technical limitations of printing fully opaque cosmetic contact lenses with iris texture of a targeted person and wearing the customized lenses to successfully masquerade as someone else and thereby gaining illegitimate access and advantages [5,8,32]. However, there are no known real-world examples of successful presentation attack of this kind [8].…”

“…when enrolling a person to national ID system, the same does not hold for practical applications like automated border control. Automatic contact lens detection would be not only faster but potentially also more accurate than manual inspection [32]. The commercial iris recognition systems by IrisGuard are promoted to have a cosmetic contact lens detection feature 2 but no objective security evaluation on their robustness has been conducted [20].…”

“…time-consuming data acquisition, additional interaction demands or unpleasant sudden active lighting stimuli. Furthermore, these kinds of techniques have been usually evaluated on limited datasets just to demonstrate a proof of concept, like in [12,32,44], or, in the worst case, have not been experimentally validated at all, like in [7,47].…”

“…Two proof-of-concept studies have suggested that 3D shape analysis of the observed iris can be indeed utilised for cosmetic contact lens detection. Connell et al [12] applied structured light projection to measure the curvature of the observed iris, while Hughes and Bowyer [32] used a stereo camera setup for recovering the 3D structure of the iris surface for cosmetic contact lens detection.…”