Effect of Smaller Fingerprint Sensors on the Security of Fingerprint Authentication

Small fingerprint sensors are necessary to be used in the small devices like smartphones, USBs, and cards. Different small devices have different sizes of fingerprint sensors. The scanned fingerprint image through a small fingerprint sensor is a partial fingerprint image instead of a whole fingerprint image, if we use a small fingerprint sensor. If the size of the partial fingerprints stored in the database decreases, the number of minutiae that are compared when matching decreases. Unfortunately, for the small number of minutiae, it is possible to construct "Masterprints". Masterprints can be used to impersonate multiple users stored in the database. If the size of a partial image is 15 % of a whole image, a Masterprint can be produced. We investigate the vulnerability of various sizes of partial images due to the Masterprint. Because sensors have different sizes, we use partial images of 9% to 48% of a whole image. Our results show that the security of partial fingerprint authentication is severely affected by the sizes of partial images and sensors. The smaller the partial image size, the larger the impostor matching rate; and the smaller the false matching rates, the steeper the impostor matching rate increases.