A secure biometric discretization scheme for face template protection

In this paper, a dynamic biometric discretization scheme based on Linnartz and Tuyls’s quantization index modulation scheme (LT-QIM) [Linnartz and Tuyls, 2003] is proposed. LT-QIM extracts one bit per feature element and takes care of the intra-class variation of the biometric features. Nevertheless, LT-QIM does not consider statistical distinctiveness between users, and thus lacks the capability of preserving the discriminative power of the original biometric features. We put forward a generalized LT-QIM scheme in such a way that it allocates multiple bits to each feature element according to a statistical distinctiveness measure of the feature. Hence, more bits are assigned to high distinctive features and fewer bits to low distinctive features. With provision for intra-class variation compensation and dynamic bit allocation by means of the statistical distinctiveness measure, the generalized scheme enhances the verification performance compared to the original scheme. Several comparative studies are conducted on two popular face data sets to justify the efficiency and feasibility of our proposed scheme. The security aspect is also considered by including a stolen-token scenario.

Research highlights
► A bits length per feature element is determined according to distinctiveness.
► An alignment component is generated to compensate intra-class variation.
► A perturbation is added to the helper in order to revoke a registered template.
► Bit string decoding is done by using a binary reflected gray code (BRGC).