Biometrics in a data stream context

• Ano de defesa: 2017
• Autor(a) principal: Pisani, Paulo Henrique
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Accelerometer biometrics; Adaptive biometric systems; Atualização de template; Biometria por acelerômetro; Data streams; Dinâmica da digitação; Fluxos de dados; Keystroke dynamics; Sistemas biométricos adaptativos; Template update
• Link de acesso: http://www.teses.usp.br/teses/disponiveis/55/55134/tde-08052017-141153/

The growing presence of the Internet in day-to-day tasks, along with the evolution of computational systems, contributed to increase data exposure. This scenario highlights the need for safer user authentication systems. An alternative to deal with this is by the use of biometric systems. However, biometric features may change over time, an issue that can affect the recognition performance due to an outdated biometric reference. This effect can be called as template ageing in the area of biometrics and as concept drift in machine learning. It raises the need to automatically adapt the biometric reference over time, a task performed by adaptive biometric systems. This thesis studied adaptive biometric systems considering biometrics in a data stream context. In this context, the test is performed on a biometric data stream, in which the query samples are presented one after another to the biometric system. An adaptive biometric system then has to classify each query and adapt the biometric reference. The decision to perform the adaptation is taken by the biometric system. Among the biometric modalities, this thesis focused on behavioural biometrics, particularly on keystroke dynamics and on accelerometer biometrics. Behavioural modalities tend to be subject to faster changes over time than physical modalities. Nevertheless, there were few studies dealing with adaptive biometric systems for behavioural modalities, highlighting a gap to be explored. Throughout the thesis, several aspects to enhance the design of adaptive biometric systems for behavioural modalities in a data stream context were discussed: proposal of adaptation strategies for the immune-based classification algorithm Self-Detector, combination of genuine and impostor models in the Enhanced Template Update framework and application of score normalization to adaptive biometric systems. Based on the investigation of these aspects, it was observed that the best choice for each studied aspect of the adaptive biometric systems can be different depending on the dataset and, furthermore, depending on the users in the dataset. The different user characteristics, including the way that the biometric features change over time, suggests that adaptation strategies should be chosen per user. This motivated the proposal of a modular adaptive biometric system, named ModBioS, which can choose each of these aspects per user. ModBioS is capable of generalizing several baselines and proposals into a single modular framework, along with the possibility of assigning different adaptation strategies per user. Experimental results showed that the modular adaptive biometric system can outperform several baseline systems, while opening a number of new opportunities for future work.