A Semiautomated Multilayer Picking Algorithm for Ice-sheet Radar Echograms Applied to Ground-Based Near-Surface Data

Snow accumulation over an ice sheet is the sole mass input, making it a primary measurement for understanding the past, present, and future mass balance. Near-surface frequency-modulated continuous-wave (FMCW) radars image isochronous firn layers recording accumulation histories. The Semiautomated Multilayer Picking Algorithm (SAMPA) was designed and developed to trace annual accumulation layers in polar firn from both airborne and ground-based radars. The SAMPA algorithm is based on the Radon transform (RT) computed by blocks and angular orientations over a radar echogram. For each echogram's block, the RT maps firn segmented-layer features into peaks, which are picked using amplitude and width threshold parameters of peaks. A backward RT is then computed for each corresponding block, mapping the peaks back into picked segmented-layers. The segmented layers are then connected and smoothed to achieve a final layer pick across the echogram. Once input parameters are trained, SAMPA operates autonomously and can process hundreds of kilometers of radar data picking more than 40 layers. SAMPA final pick results and layer numbering still require a cursory manual adjustment to correct noncontinuous picks, which are likely not annual, and to correct for inconsistency in layer numbering. Despite the manual effort to train and check SAMPA results, it is an efficient tool for picking multiple accumulation layers in polar firn, reducing time over manual digitizing efforts. The trackability of good detected layers is greater than 90%

Statistical Physics Analysis of Maximum a Posteriori Estimation for Multi-channel Hidden Markov Models

The performance of Maximum a posteriori (MAP) estimation is studied analytically for binary symmetric multi-channel Hidden Markov processes. We reduce the estimation problem to a 1D Ising spin model and define order parameters that correspond to different characteristics of the MAP-estimated sequence. The solution to the MAP estimation problem has different operational regimes separated by first order phase transitions. The transition points for $L$-channel system with identical noise levels, are uniquely determined by $L$ being odd or even, irrespective of the actual number of channels. We demonstrate that for lower noise intensities, the number of solutions is uniquely determined for odd $L$, whereas for even $L$ there are exponentially many solutions. We also develop a semi analytical approach to calculate the estimation error without resorting to brute force simulations. Finally, we examine the tradeoff between a system with single low-noise channel and one with multiple noisy channels.Comment: The paper has been submitted to Journal of Statistical Physics with submission number JOSS-S-12-0039

Vuforia v1.5 SDK: Analysis and evaluation of capabilities

This thesis goes into the augmented reality world and, being more specific in Vuforia uses, searching as an achievement the analysis of its characteristics. The first objective of this thesis is make a short explanation of what is understood by augmented reality and the actual different varieties of AR applications, and then the SDK’s features and its architecture and elements. In other hand, to understand the basis of the detection process realized by the Vuforia’s library is important to explain the approach to the considerations of image recognition, because it is the way in which Vuforia recognizes the different patterns. Another objective has been the exposition of the possible fields of applications using this library and a brief of the main steps to create an implementation always using Unity3D, due to Vuforia is only a SDK not an IDE. The reason to choose this way is due to the facilities that are provided by Unity3D when creating the application itself, because it already has implemented all necessary to access the hardware of the smartphone, as well as those that control the Vuforia’s elements. In other way, the Vuforia’s version used during the thesis has been the 1.5, but two months ago Qualcomm was launched the new 2.0 version, that it is not intended to form part of this study, although some of the most significant new capabilities are explained. Finally, the last and perhaps the most important objective have been the test and the results, where they have used three different smartphones to compare the values. Following this methodology has been possible to conclude which part of the results are due to the features and capabilities of the different smartphones and which part depends only of the Vuforia’s library.Català: Aquest projecte s’endinsa al món de la realitat augmentada, més concretament a l’anàlisi de les característiques y funcionalitats del SDK Vuforia. En primer objectiu serà posar en perspectiva el que s’entén per realitat augmentada i de les variants existents avui dia d’aplicacions que fan ús de la RA. A continuació es mencionen les característiques d’aquest SDK, la seva arquitectura i els seus elements. En aquesta part també s’han tingut en compte les consideracions de reconeixement d’imatge, ja que es la manera en la qual Vuforia realitza el reconeixement dels diferents patrons. El següent pas es tractar d’exposar els possibles camps d’aplicació d’aquesta llibreria, i una breu explicació dels principals passos per crear una aplicació sota Unity3D, tenint en compte sempre que Vuforia es només un SDK i no un IDE. La raó per escollir aquest entorn es degut a les ventatges que ofereix Unity3D a l’hora de crear l’aplicació, degut a que ja disposa de tot el necessari per accedir tant al hardware del propi dispositiu mòbil com a els propis elements que integren Vuforia. D’altra banda, la versió de Vuforia utilitzada durant el projecte ha sigut la 1.5, encara que fa poc més de dos mesos Qualcomm va alliberar la nova versió 2.0, la qual no forma part dels objectius d’aquest projecte, encara que una part de les noves funcionalitats més significatives s’exposen breument. Finalment, es conclourà amb els tests i resultats obtinguts. Per realitzar totes aquestes proves s’han utilitzat tres terminals diferents per poder comparar valors. A més, utilitzant aquest mètode, ha sigut possible concloure quina part dels resultats obtinguts es deuen a les característiques i capacitats dels diferents terminals i quina part depèn exclusivament de la pròpia llibreria Vuforia

Integrating Digital Data into Greenway Planning with Augmented Reality

Digital technologies, such as geographic information systems, are an integral part of the greenway planning process. A wealth of new technologies is evolving that provide improved data for planning and methods for evaluating the temporal and spatial qualities of a place. Augmented reality is a technology that can improve and enrich the user’s greenway experience. Augmented reality (AR) systems merge computer-generated graphics with a view of the physical world by aligning or registering computer graphics with a place. (Azuma, 1997) AR systems do not create a simulation of the physical world; rather augmented reality takes a real object or space as the foundation and incorporates computer graphics that add contextual data, information and meaning to a real object or place to deepen a person’s understanding. The paper will provide a clear background of augmented reality (AR), how it is being applied today, and describes the potential AR applications for greenway users. The goal is to provide greenway planners’ with a vision for how greenways will be used and interpreted in the future by users of AR technology

Distribution efficace des contenus dans les réseaux : partage de ressources sans fil, planification et sécurité

In recent years, the amount of traffic requests that Internet users generate on a daily basis has increased exponentially, mostly due to the worldwide success of video streaming services, such as Netflix and YouTube. While Content-Delivery Networks (CDNs) are the de-facto standard used nowadays to serve the ever increasing users’ demands, the scientific community has formulated proposals known under the name of Content-Centric Networks (CCN) to change the network protocol stack in order to turn the network into a content distribution infrastructure. In this context this Ph.D. thesis studies efficient techniques to foster content distribution taking into account three complementary problems:1) We consider the scenario of a wireless heterogeneous network, and we formulate a novel mechanism to motivate wireless access point owners to lease their unexploited bandwidth and cache storage, in exchange for an economic incentive.2) We study the centralized network planning problem and (I) we analyze the migration to CCN; (II) we compare the performance bounds for a CDN with those of a CCN, and (III) we take into account a virtualized CDN and study the stochastic planning problem for one such architecture.3) We investigate the security properties on access control and trackability and formulate ConfTrack-CCN: a CCN extension to enforce confidentiality, trackability and access policy evolution in the presence of distributed caches.Au cours de ces dernières années, la quantité de trafic que les utilisateurs Internet produisent sur une base quotidienne a augmenté de façon exponentielle, principalement en raison du succès des services de streaming vidéo, tels que Netflix et YouTube. Alors que les réseaux de diffusion de contenu (Content-Delivery Networks, CDN) sont la technique standard utilisée actuellement pour servir les demandes des utilisateurs, la communauté scientifique a formulé des propositions connues sous le nom de Content-Centric Networks (CCN) pour changer la pile de protocoles réseau afin de transformer Internet en une infrastructure de distribution de contenu. Dans ce contexte, cette thèse de doctorat étudie des techniques efficaces pour la distribution de contenu numérique en tenant compte de trois problèmes complémentaires : 1) Nous considérons le scénario d’un réseau hétérogène sans fil, et nous formulons un mécanisme pour motiver les propriétaires des points d’accès à partager leur capacité WiFi et stockage cache inutilisés, en échange d’une contribution économique.2) Nous étudions le problème centralisé de planification du réseau en présence de caches distribuées et (I) nous analysons la migration optimale du réseau à CCN; (II) nous comparons les bornes de performance d’un réseau CDN avec ceux d’un CCN, et (III) nous considérons un réseau CDN virtualisé et étudions le problème stochastique de planification d’une telle infrastructure.3) Nous considérons les implications de sécurité sur le contrôle d’accès et la traçabilité, et nous formulons ConfTrack-CCN, une extension deCCN utilisée pour garantir la confidentialité, traçabilité et l’évolution de la politique d’accès, en présence de caches distribuées

Online Privacy in Mobile and Web Platforms: Risk Quantification and Obfuscation Techniques

The wide-spread use of the web and mobile platforms and their high engagement in human lives pose serious threats to the privacy and confidentiality of users. It has been demonstrated in a number of research works that devices, such as desktops, mobile, and web browsers contain subtle information and measurable variation, which allow them to be fingerprinted. Moreover, behavioural tracking is another form of privacy threat that is induced by the collection and monitoring of users gestures such as touch, motion, GPS, search queries, writing pattern, and more. The success of these methods is a clear indication that obfuscation techniques to protect the privacy of individuals, in reality, are not successful if the collected data contains potentially unique combinations of attributes relating to specific individuals. With this in view, this thesis focuses on understanding the privacy risks across the web and mobile platforms by identifying and quantifying the privacy leakages and then designing privacy preserving frameworks against identified threats. We first investigate the potential of using touch-based gestures to track mobile device users. For this purpose, we propose and develop an analytical framework that quantifies the amount of information carried by the user touch gestures. We then quantify users privacy risk in the web data using probabilistic method that incorporates all key privacy aspects, which are uniqueness, uniformity, and linkability of the web data. We also perform a large-scale study of dependency chains in the web and find that a large proportion of websites under-study load resources from suspicious third-parties that are known to mishandle user data and risk privacy leaks. The second half of the thesis addresses the abovementioned identified privacy risks by designing and developing privacy preserving frameworks for the web and mobile platforms. We propose an on-device privacy preserving framework that minimizes privacy leakages by bringing down the risk of trackability and distinguishability of mobile users while preserving the functionality of the existing apps/services. We finally propose a privacy-aware obfuscation framework for the web data having high predicted risk. Using differentially-private noise addition, our proposed framework is resilient against adversary who has knowledge about the obfuscation mechanism, HMM probabilities and the training dataset

Omniring: Scaling Up Private Payments Without Trusted Setup - Formal Foundations and Constructions of Ring Confidential Transactions with Log-size Proofs

Monero is the largest cryptocurrency with built-in cryptographic privacy features. The transactions are authenticated using spend proofs, which provide a certain level of anonymity by hiding the source accounts from which the funds are sent among a set (known as a ring) of other accounts. Due to its similarities to ring signatures, this core cryptographic component is called Ring Confidential Transactions (RingCT). Because of its practical relevance, several works attempt to analyze the security of RingCT. However, due to the complexity of RingCT they are either informal, miss fundamental functionalities, or introduce undesirable trusted setup assumptions. Regarding efficiency, Monero currently deploys a scheme in which the size of the spend proof is linear in the ring size. This limits the ring size to only a few accounts, which in turn limits the acquired anonymity significantly and facilitates de-anonymization attacks. As a solution to these problems, we present the first complete rigorous formalization of RingCT as a cryptographic primitive. We then propose a generic construction of RingCT and prove it secure in our formal security model. By instantiating our generic construction with new efficient zero-knowledge proofs we obtain Omniring, a fully-fledged RingCT scheme in the discrete logarithm setting that provides the highest concrete and asymptotic efficiency as of today. Omniring is the first RingCT scheme which 1) does not require a trusted setup or pairing-friendly elliptic curves, 2) has a proof size logarithmic in the size of the ring, and 3) allows to share the same ring between all source accounts in a transaction, thereby enabling significantly improved privacy level without sacrificing performance. Our zero-knowledge proofs rely on novel enhancements to the Bulletproofs framework (S&P 2018), which we believe are of independent interest