Embedding Local Quality Measures in Minutiae-Based Biometric Recognition

Degradation in data quality is still a main source of errors in the modern biometric recognition systems. However, the data quality can be embedded in the recognition methods at global and local levels to build more accurate biometric systems. Local quality measures represent the quality of local parts within a biometric sample. They are either combined into a global quality measure or directly embedded into the recognition techniques. Minutiae-based comparison is the main and the most common technique used for fingerprint recognition and high-resolution palmprint recognition in various security and forensic applications. The focus of this thesis is mainly on direct incorporation of the local quality measures into the state-of-the-art minutiae-based recognition methods, particularly those based on Minutiae Cylinder-Code (MCC). Firstly, we introduce cylinder quality measures as a new type of local quality measures associated with the local minutiae descriptors. Then, we propose several methods for incorporating such local quality measures into the biometric systems, in order to improve their recognition performance. Among them is a novel and efficient quality-based consolidation method for embedding minutiae quality and cylinder quality measures in MCC based comparison methods. We also propose a supervised embedding method based on a binary classification model, which requires labeled minutiae for training. Finally, we apply a variant of the proposed consolidation method for the challenging case of latent fingerprint and palmprint identification with embedded subjective and objective minutiae quality

Estimation of cylinder quality measures from quality maps for Minutia-Cylinder Code based latent fingerprint matching

Poor quality of fingerprint data is one of the major problems concerning latent fingerprint matching in forensic applications. Local quality of fingerprint plays a very important role in this application field to ensure high recognition performance. Al- though big progress has been made in matching of fingerprints using local minutiae descriptors, in particular Minutia Cylinder- Code (MCC), automatic latent fingerprint matching continues to be a challenge. Previously we proposed a matching algo- rithm that uses minutiae information encoded by MCC with in- tegrated local quality measures associated to each MCC called cylinder quality measures. In our previous work, cylinder qual- ity measures for latent case have been proposed by combining the subjective qualities of individual minutiae involved. In this paper, we propose an alternative method to estimate the cylin- der quality measures directly from fingerprint quality maps, in particular ridge clarity maps, by taking into account the num- ber of involving minutiae as well. Integration of MCC with the proposed cylinder quality measures was evaluated through ex- periments on the latent fingerprint database NIST SD27, which show clear improvements in the identification performance of latent fingerprints of ugly quality

Privacy-Preserving Biometric Authentication

Biometric-based authentication provides a highly accurate means of authentication without requiring the user to memorize or possess anything. However, there are three disadvantages to the use of biometrics in authentication; any compromise is permanent as it is impossible to revoke biometrics; there are significant privacy concerns with the loss of biometric data; and humans possess only a limited number of biometrics, which limits how many services can use or reuse the same form of authentication. As such, enhancing biometric template security is of significant research interest. One of the methodologies is called cancellable biometric template which applies an irreversible transformation on the features of the biometric sample and performs the matching in the transformed domain. Yet, this is itself susceptible to specific classes of attacks, including hill-climb, pre-image, and attacks via records multiplicity. This work has several outcomes and contributions to the knowledge of privacy-preserving biometric authentication. The first of these is a taxonomy structuring the current state-of-the-art and provisions for future research. The next of these is a multi-filter framework for developing a robust and secure cancellable biometric template, designed specifically for fingerprint biometrics. This framework is comprised of two modules, each of which is a separate cancellable fingerprint template that has its own matching and measures. The matching for this is based on multiple thresholds. Importantly, these methods show strong resistance to the above-mentioned attacks. Another of these outcomes is a method that achieves a stable performance and can be used to be embedded into a Zero-Knowledge-Proof protocol. In this novel method, a new strategy was proposed to improve the recognition error rates which is privacy-preserving in the untrusted environment. The results show promising performance when evaluated on current datasets

On the use of convolutional neural networks for robust classification of multiple fingerprint captures

Fingerprint classification is one of the most common approaches to accelerate the identification in large databases of fingerprints. Fingerprints are grouped into disjoint classes, so that an input fingerprint is compared only with those belonging to the predicted class, reducing the penetration rate of the search. The classification procedure usually starts by the extraction of features from the fingerprint image, frequently based on visual characteristics. In this work, we propose an approach to fingerprint classification using convolutional neural networks, which avoid the necessity of an explicit feature extraction process by incorporating the image processing within the training of the classifier. Furthermore, such an approach is able to predict a class even for low-quality fingerprints that are rejected by commonly used algorithms, such as FingerCode. The study gives special importance to the robustness of the classification for different impressions of the same fingerprint, aiming to minimize the penetration in the database. In our experiments, convolutional neural networks yielded better accuracy and penetration rate than state-of-the-art classifiers based on explicit feature extraction. The tested networks also improved on the runtime, as a result of the joint optimization of both feature extraction and classification

BioTwist - overcoming severe distortions in ridge-based biometrics for successful identication

Biometrics rely on a physical trait's permanence and stability over time, as well as its individuality, robustness and ease to be captured. Challenges arise when working with newborns or infants because of the tininess and fragility of an infant's features, their uncooperative nature and their rapid growth. The last of these is particularly relevant when one tries to verify an infant's identity based on captures of a biometric taken at an earlier age. Finding a physical trait that is feasible for infants is often referred to as the infant biometric problem. This thesis explores the quality aspect of adult fingermarks and the correlation between image quality and the mark’s usefulness for an ongoing forensic investigation, and researches various aspects of the “ballprint” as an infant biometric. The ballprint, the friction ridge skin area of the foot pad under the big toe, exhibits similar properties to fingerprint but the ball possesses larger physical structures and a greater number of features. We collected a longitudinal ballprint database from 54 infants within 3 days of birth, at two months old, at 6 months and at 2 years. It has been observed that the skin of a newborn's foot dries and cracks so the ridge lines are often not visible to the naked eye and an adult fingerprint scanner cannot capture them. This thesis presents the physiological discovery that the ballprint grows isotropically during infancy and can be well approximated by a linear function of the infant's age. Fingerprint technology developed for adult fingerprints can match ballprints if they are adjusted by a physical feature (the inter-ridge spacing) to be of a similar size to adult fingerprints. The growth in ballprint inter-ridge spacing mirrors infant growth in terms of length/height. When growth is compensated for by isotropic rescaling, impressive verification scores are achieved even for captures taken 22 months apart. The scores improve even further when low-quality prints are rejected; the removal of the bottom third improves the Equal Error Rate from 1-2% to 0%. In conclusion, this thesis demonstrates that the ballprint is a feasible solution to the infant biometric problem

Embedding cylinder quality measures into Minutia Cylinder-Code based latent fingerprint matching

One of the major problems concerning latent fingerprint matching in forensic applications is the poor quality of fingerprint data. Therefore, local quality assessment of fingerprint images is necessary to ensure high biometric performance in this application field. While big progress has been made in matching of fingerprints by using local minutiae descriptors invariant to rotation and translation, in particular minutia cylinder-code (MCC), automatic latent fingerprint matching continues to be a challenge. The goal of our research is to develop a matching algorithm that uses minutiae information encoded by MCC with integrated local quality measures. In this paper, firstly, we associate a new local quality measure, called cylinder quality, to each MCC descriptor by combining the qualities of individual minutiae involved. Then, we propose a method for incorporating the cylinder qualities in latent fingerprint matching through a quality-based relaxation procedure in order to cope with challenges originating from poor-quality regions. Experimental results on NIST SD27 show that integrating the cylinder qualities through the proposed method improves the identification performance for latent fingerprints of ugly quality

Criticism in the absence of criticism

English abstract: Criticism is defined as the examination and judgment about someone or something. This definition includes, at first, an analytical task -with a particular methodology related to it- and, at second, a synthetic activity, translated into a value judgment on what is previously analyzed. Criticism can be done in different ways and depths: from the basic critical thinking -essentially descriptive- to the most truthful one –the poetic criticism-, that transcends pure description or analysis and refers itself to the internal coherence of the object. Any criticism that seeks to reduce the distance to the truth will address both to the intrinsic object relationships -or own laws- and to the extrinsic ones. Furthermore, an objective criticism provides a knowledge of the object regardless of the observer or frame of reference. This provides an effective method and a guaranteed way to approach to the knowledge of the object. Does this mean that without a regular critical method no criticism is undertaken? The proposal of this paper is to explain how a critical thought can be undertaken in the absence of criticism, in which there is no explicit value judgment. Taking the hypothesis that there is criticism in the absence of criticism, an architectural work –either being a building, a writing on architecture, etc.- that implies a tacit criticism could work on two levels: as a practical result –built, literary, etc.- and as a critical thought. The hypothesis proposes that such duality, criticism and practice, may come together in a single work. Although not in any. The existence of criticism in the absence of criticism will depend on the nature of the object and, with no doubt, on the speaker and receiver. At first glance, the guarantees provided by this criticism in the absence of criticism seem less tan through the orthodox one, in which the subject is the weakest part of the chain. However, the absence of explicit value judgment can lead to a series of stimuli –coherency, aesthetic, recreational or other- that, in certain contexts, do more viable the approach to the knowledge than through the conventional method. Spanish abstract: La crítica se define como el examen y juicio acerca de alguien o algo. Esta definición comprende, por un lado, una tarea analítica -con una determinada metodología asociada- y, por otro, una actividad sintética, traducida en un juicio de valor acerca de lo previamente analizado. La crítica puede hacerse de distinta forma y con distinto grado de profundidad: desde la más básica –fundamentalmente, la crítica descriptiva- hasta la más veraz -la crítica poética-, que trasciende la descripción o el análi sis puro y se refiere a la coherencia interna del objeto de estudio. Toda crítica que pretenda reducir la distancia de aproximación a la verdad se ocupará tanto de las relaciones intrínsecas o leyes propias del objeto como de las eelaciones extrínsecas al mismo. Por otro lado, una crítica objetiva facilita el conocimiento del objeto de estudio independientemente del observador o del marco de referencia, lo que la convierte en un método eficaz y con garantías para la aproximación al conocimiento del objeto. Pero ¿significa esto que sin crítica ortodoxa no puede existir crítica?. La propuesta de esta comunicación es dilucidar hasta qué punto puede emprenderse una crítica en ausencia de crítica, es decir, una crítica en la que no sea explícito el juicio de valor. Tomando como hipótesis el hecho de que exista crítica en ausencia de crítica, una obra arquitectónica –ya sea un edificio construido, un escrito sobre arquitectura, etc.- que implique una crítica tácita podría funcionar a dos niveles: como producto práctico -edificado, literario, etc.- y como reflexión crítica. La hipótesis planteada propone que tal dualidad, la crítica y la práctica, pueda confluir en una misma obra. Aunque no en cualquiera. La existencia de crítica en ausencia de crítica dependerá de la naturaleza de la obra y, sin lugar a dudas, del emisor y el receptor del mensaje crítico. A primera vista, las garantías que ofrece la crítica en ausencia de crítica parecen menores que mediante la crítica ortodoxa, para la que el sujeto es la parte más débil de la cadena. Sin embargo, la ausencia de juicio de valor explícito puede comportar una serie de estímulos – de coherencia, estéticos, lúdicos, prácticos o de otra índole- que, en determinados contextos, hagan más viable y clara la comprensión de la obra que a través del método convencional