Template update algorithms and their application to face recognition systems in the deep learning era

Biometric technologies and facial recognition systems are reaching a very high diffusion for authentication in personal devices and public and private security systems, thanks to their intrinsic reliability and user-friendliness. However, although deep learning-based facial features reached a significant level of compactness and expressive power, the facial recognition performance still suffers from intra-class variations such as ageing, different facial expressions, different poses and lighting changes. In the last decade, several "adaptive" biometric systems have been proposed to deal with this problem. Unfortunately, adaptive methods usually lead to a growth of the system in terms of memory and computational complexity and involve the risk of inserting impostors among the templates. The first goal of this PhD thesis is the presentation of a novel template-based self-update algorithm, able to keep over time the expressive power of a limited set of templates. This classification-selection approach overcomes the problem of manual updating and stringent computational requirements. In the second part of the thesis, we analyzed if and to what extent this "optimized" self-updating strategy improves the facial recognition performance, especially in application contexts where the facial biometric trait undergoes great changes due to the passage of time. In contexts of long-term use, in fact, the high representativeness of the deep features may not be enough and this is usually overcome with a re-enrollment phase. For this reason, one of our goals was to evaluate how much an automatic template updating system could compete with human-in-the-loop in terms of performance. To simulate situations of long-term use in which the temporal variability of biometric data is high, we acquired a new dataset collected by using frames of some videos in YouTube related to Daily Photo Projects: people take a picture every day for a certain period of time, usually to show how their appearance is changing. The temporal information present in this new dataset allowed us to evaluate how long a facial feature can remain representative depending on the context and the recognition system. Extensive experiments on different datasets and using different facial features are conducted to define the contexts of applicability and the usefulness of adaptive systems in the deep learning era

Preliminary Results on a "Real" Iris Recognition System under Challenging Operational Conditions

Iris recognition algorithms have recently demonstrated excellent performance in the authentication task. In this paper, we present a technology transfer project for the development and testing of a biometric recognition system under challenging operational conditions. Due to the stringent operational requirements, the design and implementation of the system included a phase of selecting technologically advanced hardware. The lack of corresponding data sets implied a novel acquisition step. The evaluation phase is preliminary as the data set is being expanded for the acquisition of new samples capable of highlighting the system’s critical issues. Current samples were acquired in very different lighting conditions and in the presence of glasses, which was not yet done in the literature. In addition to the selected hardware, such data allowed us to simulate a realistic environmental context for the project’s final prototype

Efficacy of Spectral Signatures for the Automatic Classification of Abnormal Ventricular Potentials in Substrate-Guided Mapping Procedures

Several peculiar spectral signatures of post-ischaemic ventricular tachycardia (VT) electrograms (EGMs) have been recently published in the scientific literature. However, despite they were claimed as potentially useful for the automatic identification of arrhythmogenic targets for the VT treatment by trans-catheter ablation, their exploitation in machine learning (ML) applications has been not assessed yet. The aim of this work is to investigate the impact of the information retrieved from these frequency-domain signatures in modelling supervised ML tools for the identification of physiological and abnormal ventricular potentials (AVPs). As such, 1504 bipolar intracardiac EGMs from nine electroanatomic mapping procedures of post-ischaemic VT patients were retrospectively labelled as AVPs or physiological by an expert electrophysiologist. In order to assess the efficacy of the proposed spectral features for AVPs recognition, two different classifiers were adopted in a 10-time 10-fold cross-validation scheme. In both classifiers, the adoption of spectral signatures led to recognition accuracy values above 81%, suggesting that the use of the frequency-domain characteristics of these signals can be successfully considered for the computer-aided recognition of AVPs in substrate-guided mapping procedures

3D Face Reconstruction for Forensic Recognition - A Survey

3D face reconstruction algorithms from images and videos are applied to many fields, from plastic surgery to the entertainment sector, thanks to their advantageous features. However, when looking at forensic applications, 3D face reconstruction must observe strict requirements that still make unclear its possible role in bringing evidence to a lawsuit. Shedding some light on this matter is the goal of the present survey, where we start by clarifying the relation between forensic applications and biometrics. To our knowledge, no previous work adopted this relation to make the point on the state of the art. Therefore, we analyzed the achievements of 3D face reconstruction algorithms from surveillance videos and mugshot images and discussed the current obstacles that separate 3D face reconstruction from an active role in forensic applications

3D Face Reconstruction: the Road to Forensics

3D face reconstruction algorithms from images and videos are applied to many fields, from plastic surgery to the entertainment sector, thanks to their advantageous features. However, when looking at forensic applications, 3D face reconstruction must observe strict requirements that still make its possible role in bringing evidence to a lawsuit unclear. An extensive investigation of the constraints, potential, and limits of its application in forensics is still missing. Shedding some light on this matter is the goal of the present survey, which starts by clarifying the relation between forensic applications and biometrics, with a focus on face recognition. Therefore, it provides an analysis of the achievements of 3D face reconstruction algorithms from surveillance videos and mugshot images and discusses the current obstacles that separate 3D face reconstruction from an active role in forensic applications. Finally, it examines the underlying data sets, with their advantages and limitations, while proposing alternatives that could substitute or complement them

Is a Genetic Variant associated with Bipolar Disorder Frequent in People without Bipolar Disorder but with Characteristics of Hyperactivity and Novelty Seeking?

Objective: The objective is to verify whether a genetic condition associated with bipolar disorder (BD) is frequent in old adults adapted to their environment, without BD, but with aptitudes for hyperactivity and novelty seeking (H/NS). Methods: In this cross-sectional study, the study sample included healthy elderly people (40 participants, aged 60 or older) living in an urban area and recruited from a previous study on physical exercise and active aging, who were compared with 21 old adults with BD from the same area. The genetic methodology consisted of blood sampling, DNA extraction, real-time PCR jointly with FRET probes, and the SANGER sequencing method. The genetic variant RS1006737 of CACNA1C, found to be associated with bipolar disorder diagnosis, was investigated. Results: The frequency of the RS1006737 genetic variant in the study group (H/NS) is not higher than in the BD group and is statistically significantly higher than in all the control groups found in the literature. However, the familiarity for BD is higher in old adults with BD than in the H/NS sample without BD. The risk of BD in the family (also considering those without BD but with family members with BD) is not associated with the presence of the genetic variant examined. Conclusion: The study suggests that the gene examined is associated with characteristics of hyperactivity rather than just BD. Nevertheless, choosing to participate in an exercise program is an excessively general way to identify H/NS. The next step would be to identify the old adults with welldefined H/NS features with an adequate tool

Exploring Transfer Learning for Ventricular Tachycardia Electrophysiology Studies

Arrhythmogenic sites in post-ischemic ventricular tachycardia (VT) are usually identified by looking for abnormal ventricular potentials (AVPs) in intracardiac electrograms (EGMs). Unfortunately, the accurate recognition of AVPs is a challenging problem for different reasons, including the intrinsic variability in the A VP waveform. Given the high performance of deep neural networks in several scenarios, in this work, we explored the use of transfer learning (TL) for AVPs detection in intracardiac electrophysiology. A balanced set of 1504 bipolar intracardiac EGMs was collected from nine post-ischemic VT patients. The time-frequency representation was generated for each EGM by computing the synchrosqueezed wavelet transform to be used in the re-training of the convolutional neural network. The proposed approach allows obtaining high recognition results, above 90% for all the investigated performance indexes, demonstrating the effectiveness of deep learning in the recognition of AVPs in post-ischemic VT EGMs and paving the way for its use in supporting clinicians in targeting arrhythmogenic sites. In addition, this study further confirms the efficacy of the TL approach even in case of limited dataset sizes

Cybersecurity and AI: The PRALab Research Experience

We present here the main research topics and activities on the design, security, safety, and robustness of machine learning models developed at the Pattern Recognition and Applications Laboratory (PRALab) of the University of Cagliari. Our findings have significantly contributed to identifying and characterizing the vulnerability of such models to adversarial attacks in the context of real-world applications and proposing robust techniques to make these models more reliable in security-critical scenarios

Fingerprint Presentation Attacks: Tackling the Ongoing Arms Race in Biometric Authentication

The widespread use of Automated Fingerprint Identification Systems (AFIS) in consumer electronics opens for the development of advanced presentation attacks, i.e. procedures designed to bypass an AFIS using a forged fingerprint. As a consequence, AFIS are often equipped with a fingerprint presentation attack detection (FPAD) module, to recognize live fingerprints from fake replicas, in order to both minimize the risk of unauthorized access and avoid pointless computations. The ongoing arms race between attackers and detector designers demands a comprehensive understanding of both the defender’s and attacker’s perspectives to develop robust and efficient FPAD systems. This paper proposes a dual-perspective approach to FPAD, which encompasses the presentation of a new technique for carrying out presentation attacks starting from perturbed samples with adversarial techniques and the presentation of a new detection technique based on an adversarial data augmentation strategy. In this case, attack and defence are based on the same assumptions demonstrating that this dual research approach can be exploited to enhance the overall security of fingerprint recognition systems against spoofing attacks

Usefulness of salivary sampling for the molecular detection of a genetic variant associated with bipolar disorders

Under certain conditions, the hyperthymic temperament traits associated with an increased risk of developing bipolar disorders may in fact produce adaptive responses. The purpose of this study is to see if the type of biological material used for genetic analysis (saliva or blood) affects the detection of mutations in the CACNA1C (RS1006737) gene. The first experimental group consisted of Sardinian migrants (“volunteers”) in South American and European megacities. The second experimental group consisted of older healthy subjects with hyperactivity and novelty-seeking characteristics from Cagliari, Italy. The genetic procedure included DNA extraction, real-time PCR, and the Sanger method. Nonetheless, the authors believe that saliva is the most appropriate biological material, given its many advantages. In contrast to blood, saliva can be collected by any type of healthcare provider after following a few simple instructions