Le développement du transport partout dans le monde a fourni un grand nombre d'avantages pour de nombreux aspects de la vie humaine. Les systèmes de transport intelligents (ITS) sont des applications avancées qui visent à rendre les réseaux de transport plus sûrs, plus pratiques et plus intelligents. Selon leurs usages, ils peuvent être classés en deux types d'applications ITS, qui sont des applications de sûreté et des applications non-sûreté. Le réseau de véhicules ad hoc (VANET) est un élément clé des systèmes ITS, car il permet la communication entre les unités de transport. Ces communications prennent en charge différentes applications ITS avec différentes propriétés. Parmi les deux types d'applications, nous nous intéressons aux applications de sûreté qui ont des contraintes de qualité de service et des contraintes de sécurité plus strictes. Selon le scénario considéré et l'application de sûreté donnée, les informations échangées entre les véhicules doivent être diffusé localement dans une communication à un seul saut et / ou également notifiées aux véhicules à large dimension. L'objectif principal de cette thèse est d'améliorer les performances des applications de sûreté en termes de qualité de service et de sécurité, à la fois dans une communication à un saut et dans une communication multi-sauts. Nous nous intéressons à la fiabilité, la connectivité et le déni de service (DoS). Nous étudions et proposons des solutions techniques provenant de couches inférieures (Physique, Liaison et Réseaux) qui jouent un rôle fondamental dans l'atténuation des défis créés par la nature de l'environnement des véhicules. Tout d'abord, nous introduisons une nouvelle méthode efficace pour fiabiliser la radiodiffusion. Dans notre système, les messages de sécurité sont rediffusés lorsque l'expéditeur est sollicité. Cela augmente le pourcentage de véhicules qui reçoivent les messages alors que le nombre de messages dupliqués reste limité. En second lieu, en tenant compte de la fragmentation du réseau, nous étudions des solutions qui permettent de pallier la déconnexion temporaire du réseau pour apporter l'information de sécurité aux destinataires. Basé sur les propriétés sociales des réseaux de véhicules, nous proposons un protocole de transfert basé sur des relations sociales pour relayer la communication entre les véhicules et des points d'intérêt qui fournissent des services de sécurité avec des contraintes de temps plus souples, telles que la recherche et le sauvetage. Troisièmement, nous étudions l'attaque de brouillage, une sorte d'attaques DoS, qui est cruciale pour les applications de sûreté et qui et facilement réalisable au niveau des couches inférieures. Nous modélisons l'attaque de brouillage afin d'étudier la dégradation causée par l'attaque sur les performances du réseau. La dégradation à un certain niveau dans les performances du réseau est une indication de présence d'attaques de brouillage dans le réseau; donc les résultats de cette analyse nous permettent de déterminer les seuils de performance du réseau pour distinguer entre les scénarios normaux et les scénarios attaqués. Toutefois, selon cette analyse, le procédé utilisant la dégradation comme une indication pour détecter une attaque de brouillage est impossible pour des applications temps réel. Par conséquent, nous proposons des nouvelles méthodes afin de détecter les attaques de brouillage temps réel. Nos méthodes permettent la détection en temps réel avec une grande précision, non seulement chez le moniteur central mais aussi au niveau de chaque véhicule. Par conséquent, les véhicules sont avertis sur l'attaque assez tôt pour récupérer la communication et réagir à ces attaques. / The development of transportation all over the world has been providing a lot of benefits for many aspects of human life. Intelligent Transportation Systems (ITS) are advanced applications that aim to make the transport networks safer, more convenient and smarter. According to their usages, they can be classified into two types of ITS applications, which are safety applications and non-safety applications. Vehicular ad hoc network (VANET) is a key component of ITS since it enables communications among transportation units. These communications support different ITS applications with various properties. Between two types of applications, we are interested in safety applications which have tighter quality and security constraints. Depending on an applied scenario of a given safety application, the exchanged information among vehicles must be broadcast locally within one-hop communication and/or also be notified to vehicles in large range. The main objective of this thesis is to improve the performance of safety applications in term of the quality of service and security, in both one-hop communication and multi-hop communication. We focus on reliability, connectivity and Denial of Services (DoS) attack. We study and propose technical solutions coming from lower layers (Physical, MAC and network layers) which play a fundamental role in mitigation to challenges created by the nature of the vehicular environment. Firstly, we introduce a reliable scheme to achieve the reliability for broadcasting. In our scheme, the safety messages are rebroadcast when the sender is solicited. This increases the percentage of vehicles receiving the messages while duplicated messages are limited. Secondly, with consideration of the fragmentation of the network, we study solutions that overcome the temporary disconnection in the network to bring the safety information to the recipients. Based on the social properties of vehicular networks, we propose a social-based forwarding protocol to support the communication between vehicles to points of interest that provide safety services with looser time constraints, such as search and rescue. Thirdly, we investigate jamming attack, a kind of DoS attacks, which is crucial for safety applications because of the adequate condition of the attack at the lower layers. We model jamming attack on broadcasting in order to study the degradation caused by the attack on network performance. The degradation at a certain level in network performance is an indication of a jamming attack presence in the network; therefore results from this analysis will allow us to determine network performance thresholds to distinguish between normal and attacked scenarios. However, according to our analysis, the method using the degradation as an indication to detect a jamming attack is not feasible for real-time applications. Hence, we propose methods to detect jamming attacks in real-time. Our methods allow real-time detection with high accuracy, not only at the central monitor but also at each vehicle. Therefore, vehicles are noticed about the attack soon enough to recover the communication and react to these attacks.

Abstract The primary mission of the Finnish Air Force is to ensure a continuous surveillance and policing of the national airspace. The wartime mission is defensive counter-air fighter operations. Implementation of the air surveillance is carried out mainly with air surveillance radars – policing and defensive actions with fighters. A foundation to a well-executed flight operation is a situation awareness. Pilots have to have a real time air picture in their use, i.e., exact information of the own and enemy’s fighters, and instructions of the mission command. The later has to have information for example about the remaining flight time of the fighters. To keep up the situation awareness the fighters participating the flight operation and the mission command on the ground are connected via real time robust communications system. In this thesis, the system development of the experimental SIHTI (Suomen ilmavoimien hajaspektritietovuo) spread spectrum data link fulfilling the national requirements is considered from the requirement specification to the performance measurements of the airproof prototype. The SIHTI system, which has to be secure, robust and having good LPD/LPI (Low Probability of Detection/Low Probability of Interception) properties has to enable bidirectional transmission between fighters and base stations as well as the fighters themselves. The SIHTI system has to operate in the case when many of similar nets are operating simultaneously in the same region and under heavy jamming. The system concept and its implementation has to be configurable so that an end user and a maintenance of the system can affect on the performance of the system only via parameters and changes in algorithms. In this thesis, it will be shown that the experimental SIHTI prototype with minor changes can fulfil the set requirements. / Tiivistelmä Suomen ilmavoimien perustehtävä on kansallisen ilmatilan jatkuva valvonta ja vartiointi sekä sodan aikana ilmatilan puolustus. Ilmatilan valvonta hoidetaan pääasiassa ilmavalvontatutkilla – vartiointi ja puolustus sotilaskoneilla. Sotilaskoneiden tehokkaan toiminnan edellytyksenä on tilannetietoisuus. Lento-operaatioon osallistuvilla tahoilla tulee olla käytettävissä ajan tasalla oleva ilmatilannekuva eli tarkat tiedot omista ja vastapuolen koneista, taistelujohdon toimintaohjeet sekä tietoa muun muassa operaatioon osallistuvien koneiden jäljellä olevasta toiminta-ajasta. Tilannetietoisuuden ylläpitäminen edellyttää, että lento-operaatioon osallistuvia lentokoneita ja maassa olevaa taistelujohtoa yhdistää reaaliaikainen varmatoiminen tiedonsiirtoyhteys. Tässä väitöskirjassa tarkastellaan kansallisen sotilasilmailun tarpeet täyttävän lentokelpoisen SIHTI (Suomen ilmavoimien hajaspektritietovuo) -hajaspektritiedonsiirtokoejärjestelmän järjestelmäkehitystä aina vaatimusmäärittelystä lentokelpoisen koelaitteiston suorituskykymittauksiin. Turvallisen, varmatoimisen ja vaikeasti tiedusteltavan tiedonsiirtojärjestelmän tulee mahdollistaa niin lentokoneiden kuin lentokoneiden ja maa-asemien välinen kaksisuuntainen sanomansiirto useiden lähekkäin toimivien verkkojen tapauksessa hyvinkin voimakkaassa tahallisessa häirinnässä. Tiedonsiirtojärjestelmässä ja sen toteutuksessa tulee olla myös riittävä määrä muunneltavuutta, jotta järjestelmän loppukäyttäjä ja järjestelmän ylläpitäjä pystyvät parametri- ja algoritmimuutoksin vaikuttamaan järjestelmän suorituskykyyn. Väitöskirjassa osoitetaan, että FH/DS-CDMA (Frequency Hopping / Direct Sequence Code Division Multiple Access)- ja TDMA (Time Division Multiple Access) -monikäyttömenetelmiin pohjautuva SIHTI-koejärjestelmä pystyy pienin muutoksin täyttämään sille asetetut vaatimukset.

In this study, various jamming techniques and their effects on detection and tracking performance have been investigated through a radar receiver simulation that models a search radar for target acquisition and single-target tracking radar during track operation. The radar is modeled as looking at airborne targets, and hence clutter is not considered. Customized algorithms have been developed for the detection of target azimuth angle, range and Doppler velocity within the modeled geometry and chosen radar parameters. The effects of varying parameters like jamming-to-signal ratio (JSR) and jamming signal`s Doppler shift have been examined in the analysis of jamming effectiveness.

Techn. Universiẗat, Diss.--Berlin, 2006.

The fast development of wireless networks, which are intrinsically exposed to eavesdropping, has created a growing concern for confidentiality. While classical cryptographic schemes require a key provided by the end-user, physical-layer security leverages the randomness of the physical communication medium as a source of secrecy. The main benefit of physical-layer security techniques is their relatively low cost and their ability to combine with any existing security mechanisms. This dissertation provides an analysis including the theoretical study of the two-way wiretap channel to obtain a better insight into how to design coding mechanisms, practical tests with experimental systems, and the design of actual codes. From a theoretical standpoint, the study confirms the benefits of combining several multi-user coding techniques including cooperative jamming, coded cooperative jamming and secret key generation. For these different mechanisms, the trade-off between reliability, secrecy and communication rate is clarified under a stringent strong secrecy metric. Regarding the design of practical codes, spatially coupled LDPC codes, which were originally designed for reliability, are modified to develop a coded cooperative jamming code. Finally, a proof-of-principle practical wireless system is provided to show how to implement a secret key generation system on experimental programmable radios. This testbed is then used to assess the realistic performance of such systems in terms of reliability, secrecy and rate.

[pt] O culture jamming é um movimento de proliferação artística de mensagens, um processo retórico de intervenção e invenção que desafia a habilidade do discurso corporativo de fazer sentido de forma previsível. A organização canadense AdBusters Media Foundation é considerada um ícone do movimento e tem como objetivo declarado o redirecionamento do fluxo de informação, da forma como as corporações exercem o poder e da maneira como o significado é produzido em nossa sociedade. Tendo em vista a importância dos estudos de anticonsumo e resistência ao consumo nos campos do Marketing e do comportamento do consumidor, o objetivo do presente trabalho é analisar, em uma perspectiva exploratória, a configuração do discurso dos spoof ads (paródias de anúncios publicitários) veiculados no site do AdBusters Media Foundation, bem como verificar se tal discurso reflete os valores e objetivos da organização jammer. Para tal, analisou-se um corpus composto por 119 spoof ads, utilizando-se o método de análise do conteúdo. Os resultados do trabalho indicam que os spoof ads se configuram como uma estratégia jammer na luta pela proteção da transparência democrática e da liberdade de expressão, contra a poluição da mente por mensagens comerciais pró-consumistas ligadas diretamente às catástrofes sociais, ambientais, financeiras e éticas que se apresentam cotidianamente. Desse modo, os spoofs refletem diretamente os valores e objetivos declarados da AdBusters Media Foundation, bem como corroboram indiretamente as críticas feitas por diversos autores à eficácia de tal estratégia. / [en] Culture jamming is movement focused on the artistic proliferation of messages, a rhetorical process of intervention and invention that defies the ability of corporate speech to make sense in a predictable way. The Canadian organization Adbusters Media Foundation is considered an icon of the movement and has as its stated objective the redirection of the flow of information, the way corporations wield power, and the way meaning is produced in our society. Given the importance of studying anticonsumption and resistance to consumption in the fields of Marketing and consumer behavior, the aim of this work is to analyze in an exploratory perspective, the configuration of the discourse of spoof ads (parodies of advertisements) served on the website of Adbusters Media Foundation, as well as verify if such discourse reflects the values and goals of the jammer organization. To do this, we analyzed a corpus comprising 119 spoof ads, employing the method of content analysis. The results indicate that the spoof ads are configured as a jammer strategy in the fight for the protection of democratic transparency and freedom of expression, against pollution of mind by commercial pro-consumerist messages directly linked to social, environmental, financial and ethical catastrophes that present themselves daily. Thus, the spoofs directly reflect the values and stated goals of the Adbusters Media Foundation, as well as indirectly corroborate the criticisms made by various authors to the effectiveness of such a strategy.

The phenomenon of culture jamming is not so well known in the Czech Republic. So I decided to focus on defining this term, which is sometimes translated as cultural sabotage. At the beginning of this dissertation work, I try to introduce important theories that are related to the central concept. I also focus on how culture jamming most often express and what forms are most common. In the part of examples of culture jamming in the world, I try to describe the important foreign culture jamming's groups, including demonstrations of their actions and performances. In the same way I map the Czech culture jamming groups. For a better illustration and approximation of the concept, the whole of this theoretical part is supplemented with a picture attachment. Part of the dissertation work is also a research part, which focuses on the mapping of culture jamming in the Czech Republic. Above all, I try to find out what are the motivations, speeches and goals of Czech cultural saboteurs.

Cross-eye jamming is an Electronic Attack (EA) technique that induces an angular error in the radar being jammed. The main benefit of cross-eye jamming is that it is effective against monopulse tracking radars, which are largely immune to other forms of jamming. The objective of this research is to gain a complete understanding of cross-eye jamming so that systems that might be developed in future can be properly specied. The main contribution of this work is a comprehensive mathematical and experimental study of retrodirective cross-eye jamming. The mathematical analysis considers all aspects of an isolated, single-loop, retrodirective cross-eye jamming engagement, thereby avoiding the approximations inherent in other cross-eye jamming analyses. Laboratory experiments that accurately represent reality by using the radar for both transmission and reception, and simulating a true retrodirective cross-eye jammer were performed to validate the theoretical analysis. Lastly, the relationship between the angular error induced in the radar being jammed and the matching required from a cross-eye jammer system is explored. The most important conclusion of this work is that the traditional analyses of cross- eye jamming are inaccurate for the conditions under which cross-eye jammers operate. These inaccuracies mean that the traditional analyses are overly conservative, particularly at short ranges and for high cross-eye gains, suggesting that practical cross-eye jammers can be realised more easily than is generally believed. / Thesis (PhD)--University of Pretoria, 2010. / Electrical, Electronic and Computer Engineering / unrestricted

Global Navigation Satellite Systems (GNSS) have found wide adoption in various applications, be they military, civilian or commercial. The susceptibility of GNSS to radio-frequency interference can, thus, be very disruptive, even for emergency services, therefore threatening people's lives. An early prototype of a system providing relatively cheap widescale GNSS jamming detection, called J911, is explored in this thesis. J911 is smartphone-based crowdsourcing of GNSS observations, most interesting of which are carrier-to-noise-density ratio (<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Cfrac%7BC%7D%7BN_0%7D" />) and Automatic Gain Control (AGC) voltage. To implement the prototype, an Android application to provide the measurements, a backend to parse and store the measurements, and a frontend to visualize the measurements were developed. In real-world use, the thesis argues, the J911 system would best be implemented over existing Enhanced 9-1-1 (E911) infrastructure, becoming a standardized part of the Public Switched Telephone Network (PSTN). The Android application, running on a smartphone, would periodically construct messages to be sent to the backend over an Internet connection. The messages would include: current location from all location providers available in Android OS, observed satellites from all supported constellations, the satellites' <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Cfrac%7BC%7D%7BN_0%7D" />, and a timestamp. Once a message is received on the backend, the data would be extracted and stored in a database. The frontend would query the database and produce a map with the collected datapoints overlaid on top of it, whose color indicates received signal strength at that point. When a jammer gets close enough to a few smartphones, they will all be jammed, which is easily observed on the map. On top of that, if enough samples are gathered, a Power Difference of Arrival localization algorithm can be used to localize the jammer. The smartphones that the system was planned to be tested with did not support AGC level readings, therefore in order to obtain AGC levels over time, a few SiGe GN3S Samplers, which are radio-frequency frontends, were used. In eastern Idaho, United States, over three nights in July 2017, an exercise, named 2017 DHS JamX, was performed with the help of the US Department of Homeland Security. Sadly, the approval for the publication of the test results did not come in time to be included in this thesis.

Les éthers de cellulose (EC) sont des agents rétenteurs d'eau très utilisés dans les matériaux de construction: ils limitent fortement la perte d'eau due principalement à l'absorption dans le substrat pendant la cure, favorisant ainsi les réactions d'hydratation du ciment nécessaires à la prise qui assurent de bonnes propriétés mécaniques pour le matériau final. Cependant les causes exactes de ce phénomène de rétention d'eau restent encore incomprises à ce jour. Dans ce travail de thèse, afin d'analyser les mécanismes de la rétention, nous tentons de mieux comprendre pourquoi et comment les transferts hydriques sont modifiés en présence d'EC. Dans un premier temps, nous montrons, grâce à des tests de filtration et par les méthodes usuelles de caractérisation (microscopie, diffusion de la lumière) que les EC en solution forment des agrégats polydisperses de plusieurs dizaines de microns de diamètre. Nous montrons ensuite qu'une solution d'EC passant à travers un matériau poreux modèle (tamis) bouche progressivement ce tamis, même si la taille de maille est nettement supérieure à celle des agrégats, du fait d'un effet de blocage statistique. Cet effet de coincement se produit également lors de l'écoulement à travers un milieu poreux 3D (empilements de billes de verre), ce qui conduit à l'arrêt du fluide après une certaine hauteur de pénétration dans le milieu. Enfin, en revenant aux tests standards de rétention avec le matériau réel (mortier) puis en les comparant au test de filtration à travers un tamis nous montrons que ce dernier est un bon test alternatif qui permet de caractériser la capacité de rétention des EC / In building materials, such as mortars, cellulose ethers (CE) are used as water-retention agents. They prevent the loss of water due to absorption into the substrate during curing stage. They maintain wet conditions for proper hardening and final properties. However, the cause of retention remains unknown. First, we show through filtration tests and usual characterization methods (microscopy, light scattering) that CE solutions are composed of polydisperse aggregates of several tens of microns in diameter. We then show that a CE solution passing through a model porous medium (sieve) progressively block the sieve, even if the mesh size is much larger than the aggregates diameter, due to a statistical effect of blocking. This jamming effect also occurs during the flow through a 3D porous medium (stacks of glass beads), which led to the stopping of the fluid after a certain penetration depth of the medium. Finally, coming back to the retention standard tests with the real material (mortar) and comparing them to the filtration test we show that the latter is a good alternative test to characterize the CE retention capacity