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Dissertations / Theses on the topic 'Giant magnetoresistance (GMR) sensor'
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1
Chalastaras, Athanasios. "Giant magnetoresistance in magnetic multilayers using a new embossed surface." ScholarWorks@UNO, 2004. http://louisdl.louislibraries.org/u?/NOD,137.
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Thesis (M.S.)--University of New Orleans, 2004.<br>Title from electronic submission form. "A thesis ... in partial fulfillment of the requirements for the degree of Master of Science in the Department of Physics."--Thesis t.p. Vita. Includes bibliographical references.
2
Östling, Johan. "High Accuracy Speed and Angular Position Detection by Dual Sensor." Thesis, Uppsala universitet, Fasta tillståndets fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-365726.
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For many decades there has been a need in many industries to measure speed and position of ferrous gears. This is commonly done by converting passing gear teeth from trigger wheels to electrical impulses to calculate speed and angular position. By using Hall effect sensors or Giant Magnetoresistance sensors (GMR), a zero speed detection of gear teeth is possible while at the same time be cheap to produce and durable for harsh environments. A specially designed trigger-wheel (cogwheel created for measurements) with gear teeth in a specific pattern, exact position can be detected by using a dual sensor, even when no earlier information is available. The new design of trigger-wheel also makes this new method more accurate and universal compared to previous solutions. This thesis demonstrates and argues for the advantages of using a dual sensor for speed and angular position detection on gear wheels. Were one sensor do quantitative measurements for pattern detection in the teeth arrangements and the other sensor do qualitative measurements for position detection.
3
Hadadeh, Fawaz. "3D Probe for Magnetic Imaging and Non-destructive Testing." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS421/document.
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La thèse est dédiée au développement des sondes à base de capteurs magnétorésistifs capable de détecter les trois composantes du champ simultanément pour le contrôle non destructif par courants de Foucault et pour l’imagerie magnétique. Une première partie donne un aperçu de l’état de l’art des capteurs et des méthodes d’imagerie et du contrôle. Dans une seconde partie, la réalisation des sondes trois axes est donnée. Cela a inclus la micro fabrication, la réalisation de l’électronique de lecture, la conception et la réalisation de la partie mécanique et d’émission. Pour cela un travail important de simulation a été nécessaire. L’application de ces sondes sur des cas modèle pour l’imagerie magnétique avec une résolution submillimétrique est ensuite décrite. La sonde proposée dans cette thèse a été aussi utilisée avec succès pour détecter des défauts dans des échantillons d'aluminium et de titane avec un bon rapport signal sur bruit<br>The thesis is dedicated to the development of probes based on magnetoresistive sensors capable of detecting the three components of the field simultaneously for eddy current non-destructive testing and for magnetic imaging. A first part provides an overview of the state of the art of sensors, and imaging and control methods. In a second part, the realization of the three-axis probes is given. This included the micro-fabrication, the realization of the reading electronics, the design and realization of the mechanical part and emission. For this, an important simulation work was necessary. The application of these probes to model cases for magnetic imaging with submillimeter resolution is then described. The probe proposed in this thesis has also been used successfully to detect defects in aluminum and titanium samples with a good signal-to-noise ratio
4
Binder, Jörg. "Giant Magnetoresistance - eine ab-initio Beschreibung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2001. http://nbn-resolving.de/urn:nbn:de:swb:14-997704395015-96808.
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Die vorliegende Arbeit ist ein Beitrag zur Theorie des spinabhängigen Transports in magnetischen Vielfachschichten. Es wird erstmalig eine parameterfreie Beschreibung des Giant Magnetoresistance (GMR) vorgelegt, welche detaillierte Einsichten in die mikroskopischen Vorgänge gestattet. Die ab-initio Berechnung der Elektronenstruktur der magnetischen Vielfachschichten basiert auf der Spindichtefunktionaltheorie unter Verwendung eines Screened Korringa-Kohn-Rostoker-Verfahrens. Die Streueigenschaften von Punktdefekten werden über die Greensche Funktion des gestörten Systems selbstkonsistent bestimmt. Die Transporteigenschaften werden durch Lösung der quasiklassischen Boltzmann-Gleichung unter Berücksichtigung der Elektronenstruktur der Vielfachschicht und der Anisotropie der Streuung an Fremdatomen berechnet. Die Boltzmann-Gleichung wird iterativ unter Einbeziehung der Vertex-Korrekturen gelöst. Der Formalismus wird auf Co/Cu- und Fe/Cr-Vielfachschichten, die Standardsysteme der Magnetoelektronik, angewandt. Es werden die Abhängigkeit der Streuquerschnitte, der spezifischen Restwiderstände und des GMR von der Art und der Lage der Übergangsmetalldefekte in Co/Cu- und Fe/Cr-Vielfachschichten diskutiert. Darüber hinaus wird der Einfluß des Quantum Confinements auf den GMR eingehend untersucht. Vorteile und Grenzen der vorliegenden theoretischen Beschreibung werden aufgezeigt<br>A new theoretical concept to study the microscopic origin of Giant Magnetoresistance (GMR) from first principles is presented. The method is based on ab-initio electronic structure calculations within the spin density functional theory using a Screened Korringa-Kohn-Rostoker method. Scattering at impurity atoms in the multilayers is described by means of a Green's-function method. The scattering potentials are calculated self-consistently. The transport properties are treated quasi-classically solving the Boltzmann equation including the electronic structure of the layered system and the anisotropic scattering. The solution of the Boltzmann equation is performed iteratively taking into account both scattering out and scattering in terms (vertex corrections). The method is applied to Co/Cu and Fe/Cr multilayers. Trends of scattering cross sections, residual resistivities and GMR ratios are discussed for various transition metal impurities at different positions in the Co/Cu or Fe/Cr multilayers. Furthermore the relation between spin dependence of the electronic structure and GMR as well as the role of quantum confinement effects for GMR are investigated. Advantages and limits of the approach are discussed in detail
5
Binder, Jörg. "Giant Magnetoresistance - eine ab-initio Beschreibung." Doctoral thesis, Technische Universität Dresden, 2000. https://tud.qucosa.de/id/qucosa%3A24782.
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Die vorliegende Arbeit ist ein Beitrag zur Theorie des spinabhängigen Transports in magnetischen Vielfachschichten. Es wird erstmalig eine parameterfreie Beschreibung des Giant Magnetoresistance (GMR) vorgelegt, welche detaillierte Einsichten in die mikroskopischen Vorgänge gestattet. Die ab-initio Berechnung der Elektronenstruktur der magnetischen Vielfachschichten basiert auf der Spindichtefunktionaltheorie unter Verwendung eines Screened Korringa-Kohn-Rostoker-Verfahrens. Die Streueigenschaften von Punktdefekten werden über die Greensche Funktion des gestörten Systems selbstkonsistent bestimmt. Die Transporteigenschaften werden durch Lösung der quasiklassischen Boltzmann-Gleichung unter Berücksichtigung der Elektronenstruktur der Vielfachschicht und der Anisotropie der Streuung an Fremdatomen berechnet. Die Boltzmann-Gleichung wird iterativ unter Einbeziehung der Vertex-Korrekturen gelöst. Der Formalismus wird auf Co/Cu- und Fe/Cr-Vielfachschichten, die Standardsysteme der Magnetoelektronik, angewandt. Es werden die Abhängigkeit der Streuquerschnitte, der spezifischen Restwiderstände und des GMR von der Art und der Lage der Übergangsmetalldefekte in Co/Cu- und Fe/Cr-Vielfachschichten diskutiert. Darüber hinaus wird der Einfluß des Quantum Confinements auf den GMR eingehend untersucht. Vorteile und Grenzen der vorliegenden theoretischen Beschreibung werden aufgezeigt.<br>A new theoretical concept to study the microscopic origin of Giant Magnetoresistance (GMR) from first principles is presented. The method is based on ab-initio electronic structure calculations within the spin density functional theory using a Screened Korringa-Kohn-Rostoker method. Scattering at impurity atoms in the multilayers is described by means of a Green's-function method. The scattering potentials are calculated self-consistently. The transport properties are treated quasi-classically solving the Boltzmann equation including the electronic structure of the layered system and the anisotropic scattering. The solution of the Boltzmann equation is performed iteratively taking into account both scattering out and scattering in terms (vertex corrections). The method is applied to Co/Cu and Fe/Cr multilayers. Trends of scattering cross sections, residual resistivities and GMR ratios are discussed for various transition metal impurities at different positions in the Co/Cu or Fe/Cr multilayers. Furthermore the relation between spin dependence of the electronic structure and GMR as well as the role of quantum confinement effects for GMR are investigated. Advantages and limits of the approach are discussed in detail.
6
Theodoropoulou, Nikoleta. "Experimental studies of spin dependent phenomena in Giant Magnetoresistance (GMR) and Dilute Magnetic Semiconductor (DMS) systems." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE0000615.
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Stirk, Stewart. "Emissivity - a remote sensor of giant magnetoresistance with spatial resolution." Thesis, University of York, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442364.
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Wang, G. A., S. Nakashima, S. Arai, T. Kato, and S. Iwata. "High sensitivity giant magnetoresistance magnetic sensor using oscillatory domain wall displacement." American Institute of Physics, 2010. http://hdl.handle.net/2237/14167.
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Carroll, Turhan Kendall. "Radiation Damage in GMR Spin Valves." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1281633368.
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Kim, Woochan. "Integrated Current Sensor using Giant Magneto Resistive (GMR) Field Detector for Planar Power Module." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/46064.
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Conventional wire bond power modules have limited application for high-current operation, mainly because of their poor thermal management capability. Planar power modules have excellent thermal management capability and lower parasitic inductance, which means that the planar packaging method is desirable for high-power applications. For these reasons, a planar power module for an automotive motor drive system was developed, and a gate-driver circuit with an over-current protection was planned to integrate into the module. This thesis discusses a current-sensing method for the planar module, and the integrated gate driver circuit with an over-current protection. After reviewing several current-sensing methods, it becomes clear that most popular current-sensing methods, such as the Hall-Effect sensor, the current transformer, the Shunt resistor, and Rogowski coils, exhibit limitations for the planar module integration. For these reasons, a giant magneto resistive (GMR) magnetic-field detector was chosen as a current-sensing method.
The GMR sensor utilizes the characteristics of the giant magneto resistive (GMR) effect in that it changes its resistance when it is exposed to the magnetic-flux. Because the GMR resistor can be fabricated at the wafer level, a packaged GMR sensor is very compact when compared with conventional current sensors. In addition, the sensor detects magnetic-fields, which does not require direct contact to the current-carrying conductor, and the bandwidth of the sensor can be up to 1 MHz, which is wide enough for the switching frequencies of most of motor drive applications. However, there are some limiting factors that need to be considered for accurate current measurement:
â ¢ Operating temperature
â ¢ Magnetic-flux density seen by a GMR resistor
â ¢ Measurement noise
If the GMR sensor is integrated into the power module, the ambient temperature of the sensor will be highly influenced by the junction temperature of the power devices. Having a consistent measurement for varying temperature is important for module-integrated current sensors. An experiment was performed to see the temperature characteristics of a GMR sensor. The measurement error caused by temperature variation was quantified by measurement conditions. This thesis also proposes an active temperature error compensation method for the best use of the GMR sensor.
The wide current trace of the planar power module helps to reduce the electrical/thermal resistance, but it hinders having a strong and constant magnetic-field-density seen by the GMR sensor. In addition, the eddy-current effect will change the distribution of the current density and the magnetic-flux-density. These changes directly influence the accurate measurement of the GMR sensor. Therefore, analyzing the magnetic-flux distribution in the planar power module is critical for integrating the GMR sensor.
A GMR sensor is very sensitive to noise, especially when it is sensing current flowing in a wide trace and exposed to external fields, neither of which can be avoided for the operation of power modules. Post-signal processing is required, and the signal-conditioning circuit was designed to attenuate noise. The signal-conditioning circuit was designed using an instrumentation amplifier, and the circuit attenuated most of the noise that hindered accurate measurement. The over-current protection circuit along with the gate driver circuit was designed, and the concept was verified by experiments. The main achievements of this study can be summarized as:
â ¢ Characterization of conventional current-sensing methods
â ¢ Temperature characterization of the GMR resistor
â ¢ Magnetic-flux distribution of the planar power module
â ¢ Design of the signal-conditioning circuit and over-current protection circuit<br>Master of Science
11
Guenther, Justin. "Magnetoresistance in Permalloy/GaMnAs Circular Microstructures." Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1407772238.
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Herreros, Quentin. "Very low field magnetic resonance imaging." Phd thesis, Université René Descartes - Paris V, 2013. http://tel.archives-ouvertes.fr/tel-01064053.
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The aim of this thesis is to perform Magnetic Resonance Imaging at very low field (from 1 mT to 10 mT). A new kind of sensor called "mixed sensor" has been used to achieve a good detectivity at low frequencies. Combining a superconducting loop and a giant magnetoresistance, those detectors have a competitive equivalent field noise compared to existing devices (Tuned coils, SQUIDs and Atomic Magnetometers). They have been combined with flux transformers to increase the coupling between the sample and the sensor. A complete study has been performed to adapt it to mixed sensors and then maximize the gain. This set has been incorporated in an existing small MRI device to test its robustness in real conditions. In parallel, several MRI sequences (GE, SE, FLASH, EPI, ...) have been integrated and adapted to very low field requirements. They have been used to perform in-vivo three dimensional imaging and relaxometry studies on well known products to test their reliability. Finally, a larger setup adapted for full-head imaging has been designed and built to perform images on a larger working volume.
13
Ickitidze, L. P., and A. N. Mironyuk. "Planar Superconducting Magnetic Flux Transformer with Micro- and Nanosized Branches." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35455.
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The object of the study is a superconducting film magnetic flux transformer comprising two square
shaped loops with the tapering active strips and a magnetosensitive film element between them. It is
shown that splitting of the active strips into parallel micro- and nanosized superconducting branches and
slits increases the gain factor of the transformer, i. е., the concentration of an external magnetic field on
the magnetosensitive element, by a factor of more than six.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35455
14
REDON, OLIVIER. "Comportements magnetiques dans les systemes multicouches et granulaires ag/feni et ag/feco pour le developpement de capteurs magnetoresistifs." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10094.
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L'analyse des comportements magnetiques et de transport dans les systemes multicouches necessite l'introduction, en sus du couplage bilineaire, d'un terme de couplage biquadratique, favorisant l'apparition de structures magnetiques non colineaires. Les implications de ce terme supplementaire sont tres importantes, notamment au niveau des caracteristiques de transport puisqu'il agit sur des criteres aussi divers que l'amplitude de gmr, la linearite ou la tenue thermique. Nous avons pu quantifier son intensite et trouver ses origines, qui sont principalement liees a des imperfections structurales (ponts ferromagnetiques ou impuretes dans la couche non magnetique). Par une etude systematique de couches a gradient d'epaisseur, nous avons pu optimiser la sensibilite de capteurs de champs. L'etude des systemes granulaires, formes par co-deposition de materiaux magnetiques et non magnetiques, s'est averee autrement plus complexe etant donnee la structure fortement desordonnee. Neanmoins nous avons pu mettre en evidence 4 regimes de transport distincts associes aux divers comportements des aimantations dans les grains. Nous avons correle les proprietes structurales et de transport dans ces alliages granulaires par un modele prenant en compte la topologie reelle des grains et les couplages entre clusters. Enfin nous avons pu degager les parametres importants pour des applications potentielles dans le domaine de l'electrotechnique
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Váňa, Dominik. "Využití uměle vytvořeného slabého magnetického pole pro navigaci ve 3D prostoru." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2020. http://www.nusl.cz/ntk/nusl-413205.
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This master's thesis focuses on the utilization of an artificially created weak magnetic field for navigation in 3D space. The theoretical part of this work deals with the general properties of the magnetic field and with its description. The next section of the theoretical part contains an overview of measuring principles for magnetic field measurements. Based on various types of measuring principles, the thesis elaborates on commercially available miniature sensors for magnetic field measurement with a measuring range up to 10 mT. The work focuses mainly on the magnetoresistive principle and fluxgate sensors. Furthermore, the theoretical part contains descriptions of methods for modeling the magnetic field of simple permanent magnets and various magnet assemblies. Lastly, the theoretical part involves a patent search of devices used for locating magnets that are installed in an intramedullary nail, which is used in intramedullary stabilization used on fractures of human bones. By locating the magnet in the nail, it is possible to precisely determine the position of the mounting holes. The practical part of the thesis deals with the analysis of magnetic field behavior in the vicinity of various magnetic assemblies, which were modeled in COMSOL Multiphysics using the finite element method. The models were created with the aim of analysing the behaviour of the magnetic field in the vicinity of the magnets and at the same time to find possible analytical functions that could be used to determine the position of the magnet in space relative to the probe. The result of this work is an analysis of various assemblies, which contains graphs of different dependencies and prescription of polynomial functions that approximate these dependencies. Another part of the thesis is the design of a probe that serves to locate the magnetic target. The work describes two possible methods of localization. For the differential method, a user interface in LabVIEW was created. The probe based on this method is fully capable of locating the magnet in the 2D plane. The state space search method is described only in theory.
16
Melzer, Michael. "Stretchable Magnetoelectronics." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-191026.
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In this work, stretchable magnetic sensorics is successfully established by combining metallic thin films revealing a giant magnetoresistance effect with elastomeric materials. Stretchability of the magnetic nanomembranes is achieved by specific morphologic features (e.g. wrinkles), which accommodate the applied tensile deformation while maintaining the electrical and magnetic integrity of the sensor device. The entire development, from the demonstration of the world-wide first elastically stretchable magnetic sensor to the realization of a technology platform for robust, ready-to-use elastic magnetoelectronics with fully strain invariant properties, is described. The prepared soft giant magnetoresistive devices exhibit the same sensing performance as on conventional rigid supports, but can be stretched uniaxially or biaxially reaching strains of up to 270% and endure over 1,000 stretching cycles without fatigue. The comprehensive magnetoelectrical characterization upon tensile deformation is correlated with in-depth structural investigations of the sensor morphology transitions during stretching.
With their unique mechanical properties, the elastic magnetoresistive sensor elements readily conform to ubiquitous objects of arbitrary shapes including the human skin. This feature leads electronic skin systems beyond imitating the characteristics of its natural archetype and extends their cognition to static and dynamic magnetic fields that by no means can be perceived by human beings naturally. Various application fields of stretchable magnetoelectronics are proposed and realized throughout this work. The developed sensor platform can equip soft electronic systems with navigation, orientation, motion tracking and touchless control capabilities. A variety of novel technologies, like smart textiles, soft robotics and actuators, active medical implants and soft consumer electronics will benefit from these new magnetic functionalities.
17
Vovk, Vitaliy [Verfasser]. "Thermal stability of Py/Cu and Co/Cu giant magnetoresistance (GMR) multilayer systems / von Vitaly Vovk." 2007. http://d-nb.info/990687384/34.
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洪惠君. "Improvement of sensitivity of giant magnetoresistance sensor under small magnetic field." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/23010546306035574807.
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Mahesh, R. "Solid State Chemistry Of Transition Metal Oxides With Fascinating Properties." Thesis, 1996. https://etd.iisc.ac.in/handle/2005/1947.
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O'Gorman, Brian Curtin. "Spin-polarized transport in magnetic nanostructures." Thesis, 2009. http://hdl.handle.net/2152/ETD-UT-2009-12-550.
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Two of the principal phenomena observed and exploited in the field of spintronics are giant magnetoresistance (GMR) and spin transfer torque (STT). With GMR, the resistance of a magnetic multilayer is affected by the relative orientation of its magnetic layers due to (electron) spin dependent scattering. For the STT effect, a spin-polarized electric current is used to alter the magnetic state of a ferromagnet. Together, GMR and STT are at the foundation of numerous technologies, and they hold promise for many more applications. To achieve the high current densities (~10¹² A/m²) that are necessary to observe STT effects, point contacts – constricted electrical pathways (~1–100 nm in diameter) between conducting materials – are often used because of their small cross-sectional areas. In this sense, we have explored STT in bilayer magnetic nanopillars, where an electric current was used to induce precession of a ferromagnetic layer. This precessional state was detected as an increase in resistance of the device, akin to GMR. Temperature dependent measurements of the onset of precession shed light on the activation mechanism, but raised further questions about its detailed theory. Point contacts can also be used as local sources or detectors of electrons. In this context, we have observed transverse electron focusing (TEF) in a single crystal of bismuth. TEF is a k-selective technique for studying electron scattering from within materials. Using lithographically fabricated point contacts, we have studied the temperature dependence of the relaxation time for ballistic electrons from 4.2 to 100 K. These measurements indicated a transition between electron-electron dominated scattering at low temperatures and electron-phonon scattering as the Debye temperature was approached. We present preliminary work toward a TEF experiment to measure spin dependent scattering from a non-magnet/magnet interface. We also investigated spin wave propagation in thin, magnetic waveguide structures. At the boundary between the waveguide and continuous magnetic film, spin wave rays were found to radiate into the film, or to reflect and form standing waves in the waveguide. A circular defect in the waveguide was observed to cause diffraction of spin waves, generating an interference pattern of higher modes of oscillation.<br>text
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Mahesh, R. "Solid State Chemistry Of Transition Metal Oxides With Fascinating Properties." Thesis, 1996. http://etd.iisc.ernet.in/handle/2005/1947.
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Mateos, Santillan Edgar. "Side Channel Analysis of a Java-based Contactless Smart Card." Thesis, 2012. http://hdl.handle.net/10012/6685.
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Smart cards are widely used in different areas of modern life including identification, banking, and transportation cards. Some types of cards are able to store data and process information as well. A number of them can run cryptographic algorithms to enhance the security of their transactions and it is usually believed that the information and values stored in them are completely safe. However, this is generally not the case due to the threat of the side channel. Side channel analysis is the process of obtaining additional information from the internal activity of a physical device beyond that allowed by its specifications. There exist different techniques to attempt to obtain information from a cryptosystem using other ways than the normally permitted. This thesis presents a series of experiments intended to study the side channel from a particular type of smart card, known as Java Cards. This investigation uses the well known technique, Correlation Analysis, and a new type of side channel attack called fast correlation in the frequency domain to study the side channel of Java Cards. This research presents a giant magnetoresistor (GMR) probe and for the first time, this type of sensor is used to investigate the side channel. A novel setup designed for studying the side channel of smart cards is described and two metrics used to evaluate the analysis results are presented. After testing the GMR probe and methodology on electronic devices executing the Advanced Encryption Standard (AES), such as 8 bit microcontrollers and 128 bit AES implementations on FPGAs, these techniques were applied to analyse two different models of Java Cards working in the contactless mode. The results show that successful attacks on a software implementation of AES running on both models of Java Cards are possible.