Universal Fingerprint Alignment for Biometric Cryptosystems

Stouch, D.

The 3rd Boston University Student Conference on Information Assurance and Cyber Security, Boston, MA (December)

The goal of biometric cryptosystems is to encrypt some critical data using a biometric template such as the user’s fingerprint as a key. In this manner the data can only be recovered using the same biometric from the same person. Nearly all cryptosystems that use fingerprint biometrics to secure information require the query fingerprint to be pre-aligned with the reference fingerprint before the biometric features are extracted in order for the biometric representation to be used successfully as a cryptographic key during the decoding process. This is not the case in traditional biometric use for identification or verification, since in these cases the query and reference templates can be compared directly to determine the best alignment for minimizing the distance between features to determine if a match exists. This pre-alignment is a critical limitation of many biometric cryptosystems, and a novel approach to solving this problem is proposed in this paper.

In this paper, we explore an algorithm which provides a method for aligning multiple fingerprints from the same person without explicitly having the companion fingerprints to compare them with. The technique involves locating the centroid of the fingerprint using focal points of individual ridge lines. A primary radial is then identified based on the class of fingerprint (whorl, loop, arch, etc.). This radial originates at the centroid and serves as reference angle for specifying the location of the minutiae features in polar coordinates. A scaling factor is computed based on the average inter-ridge distance throughout the image. Using these three alignment techniques, the minutiae can be described as a set of feature vectors in the form (r, θ, t), where r is the scalar distance form the centroid, θ is the radial angle of the minutiae, and t is a hash value for the specific minutiae type.

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