Master's thesis deals with the security risks of current authentication methods. There are described methods which are based on user's knowledge and ownership of authentication object and biometric authentication method. The practical part of this Master's thesis deals with a specific design of authentication system based on protocol ACP, when the user proves his identity by smart card on provider assets, which is represented by ACP portal on the user's computer.

This thesis deals with the principles of network traffic obfuscation, in order to avoid its detection by the Intrusion Detection System installed in the network. At the beginning of the work, reader is familiarized with the fundamental principle of the basic types of IDS and introduced into the matter of obfuscation techniques, that serve as stepping stone in order to create our own library, whose design is described in the last part of the work. The outcome of the work is represented by a library, that provides all the implemented techniques for further use. The library can be well utilized in penetration testing of the new systems or used by the attacker.

The subject of this thesis is to study available security protocols and tools for their verification. The first part is devoted to briefly describe the concepts related to the area of security protocols and verification logics. The second part directly lists various protocols, along with attacks and errors found in design. Next chapter describes the most important tools for automatic analysis of security protocols in more detail. The main part deals with verification of security protocols selected in the chosen tool called Scyther. In conclusion, examples of multiprotocol attacks along with a summary table are displayed.

Depuis toujours, l’homme agit sur le milieu naturel pour développer son cadre de vie. Ce comportement peut avoir des effets néfastes sur l’environnement, de sorte que l’idée de le protéger a progressivement émergé dans la conscience collective. Le législateur français a ainsi développé un important arsenal législatif parmi lequel figurent des dispositions d’ordre pénal ayant vocation à sanctionner les auteurs d’atteintes à l’environnement. Mais le dispositif pénal, bien que nécessaire, ne doit pas être l’unique réponse aux atteintes à l’environnement. Il doit s’articuler avec d’autres mécanismes, tels que la responsabilité civile, et ce afin de permettre notamment la réparation du préjudice écologique. Le droit pénal de l’environnement tel qu’il est aujourd’hui mis en œuvre n’est pas satisfaisant. Il souffre d’imperfections qui affectent son efficacité. Les présents travaux tentent de remédier à cette situation. / Traditionally, the human being has acted on nature to develop its living environment. This behaviour can have bad effects on the environment, so that the idea of protecting it gradually came into the collective consciousness. The French legislature thus developed an important arsenal of laws among which we can find penal provisions made to sanction those who damage environment. But the penal system, while necessary, should not be the only answer to the environment attacks. It must be linked with other mechanisms, such as civil liability, and that in order to allow, among others, the repair of the ecological damage. Criminal law for the environment as it is implemented today is not satisfactory. It suffers from flaws that affect its efficiency. The present works try to find a remedy for this situation.

Um die ständig wachsenden Anforderungen zur Übertragung von Live Video Streams im Internet zu erfüllen werden kosteneffektive und resourceneffiziente Lösungen benötigt. Eine adäquate Lösung bietet die Peer-to-Peer (P2P) Streaming Architektur an, welche bereits heute in unterschiedlichsten Systemen zum Einsatz kommt. Solche Systeme erfordern von der Streaming Quelle nur moderate Bandbreiten, da die Nutzer (bzw. Peers) ihre eigene Bandbreite zur Verbreitung des Streams einbringen. Dazu werden die Peers oberhalb der Internetarchitektur zu einem Overlay verbunden. Das geplante Verlassen, sowie der ungewollte Absturz von Peers (genannt Churn) kann das Overlay schädigen und den Empfang einiger Peers unterbrechen. Weitaus kritischer sind Angriffe auf die Verfügbarkeit des Systems indem relevante Knoten des Overlays von Angreifern attackiert werden, um die Verteilung des Streams gezielt zu stören. Um Overlays zu konstruieren, die robust gegenüber Churn sind, nutzen so genannte pull-basierte P2P Streaming Systeme eine Mesh Topologie um jeden Peer über mehrere Pfade mit der Quelle zu verbinden. Peers fordern regelmäßig Teile des Videos, sog. Chunks, von ihren Partnern im Overlay an. Selbst wenn einige Partner plötzlich nicht mehr im System verfügbar sind kann ein Peer alle Chunks von den verbleibenden Nachbarn beziehen. Um dies zu ermöglichen tauschen Peers regelmäßig sog. Buffer Maps aus. Diese kleinen Pakete enthalten Informationen über die Verfügbarkeit von Chunks im Puffer eines Peers. Um dadurch entstehende Latenzen und den zusätzlichen Mehraufwand zu reduzieren wurden hybride Systeme entwickelt. Ein solches System beginnt pull-basiert und formt mit der Zeit einen Baum aus einer kleinen Untermenge aller Peers um Chunks ohne explizite Anfrage weiterzuleiten. Unglücklicherweise sind sowohl pull-basierte, als auch hybride Systeme anfällig gegenüber Denial-of-Service Angriffen (DoS). Insbesondere fehlen Maßnahmen zur Abschwächung von DoS Angriffen auf die Partner der Quelle. Die genannten Angriffe werden weiterhin dadurch erleichtert, dass die Identität der Quelle-nahen Knoten akkurat aus den ausgetauschten Buffer Maps extrahiert werden kann. Hybride Systeme sind außerdem anfällig für Angriffe auf den zugrundeliegenden Baum. Aufgrund der schwerwiegenden Auswirkungen von DoS Angriffen auf pull-basierte, sowie hybride Systeme stellen wir drei Gegenmaßnahmen vor. Zuerst entwickeln wir das Striping Schema zur Abschwächung von DoS Angriffen auf die Partner der Quelle. Hierbei werden Peers dazu angeregt ihre Chunk-Anfragen an unterschiedliche Partner zu senden. Als zweites entwickeln wir das SWAP Schema, welches Peers dazu bringt proaktiv ihre Partner zu wechseln um Angreifer daran zu hindern die Quellenahe zu identifizieren. Als drittes entwickeln wir RBCS, einen widerstandsfähigen Baum zur Abschwächung von DoS Angriffen auf hybride Systeme. Da bisher kein Simulator für die faire Evaluation von P2P-basierten Live Video Streaming Algorithmen verfügbar war, entwickeln wir OSSim, ein generalisiertes Simulations-Framework für P2P-basiertes Video Streaming. Des weiteren entwickeln wir etliche Angreifermodelle sowie neuartige Resilienzmetriken on OSSim. Ausgiebige Simulationsstudien zeigen, dass die entwickelten Schemata signifikant die Widerstandsfähigkeit von pull-basierten und hybriden Systemen gegenüber Churn und DoS Angriffen erhöhen. / The constantly growing demand to watch live videos over the Internet requires streaming systems to be cost-effective and resource-efficient. The Peer-to-Peer (P2P) streaming architecture has been a viable solution with various deployed systems to date. The system only requires a modest amount of bandwidth from the streaming source, since users (or peers) contribute their bandwidth to disseminate video streams. To enable this, the system interconnects peers into an overlay. However, churn–meaning the leaving and failing of peers–can break the overlay, making peers unable to receive the stream. More severely, an adversary aiming to sabotage the system can attack relevant nodes on the overlay, disrupting the stream delivery. To construct an overlay robust to churn, pull-based P2P streaming systems use a mesh topology to provide each peer with multiple paths to the source. Peers regularly request video chunks from their partners in the overlay. Therefore, even if some partners are suddenly absent, due to churn, a peer still can request chunks from its remaining partners. To enable this, peers periodically exchange buffer maps, small packets containing the availability information of peers’ video buffers. To reduce latency and overhead caused by the periodic buffer map exchange and chunk requests, hybrid systems have been proposed. A hybrid system bootstraps from a pull-based one and gradually forms a tree backbone consisting of a small subset of peers to deliver chunks without requests. Unfortunately, both pull-based and hybrid systems lack measures to mitigate Denial-of-Service (DoS) attacks on head nodes (or the source’s partners). More critically, they can be identified accurately by inferring exchanged buffer maps. Furthermore, hybrid systems are vulnerable to DoS attacks on their backbones. Since DoS attacks can badly affect both pull-based and hybrid systems, we introduce three countermeasures. First, we develop the striping scheme to mitigate DoS attacks targeting head nodes. The scheme enforces peers to diversify their chunk requests. Second, to prevent attackers from identifying head nodes, we develop the SWAP scheme, which enforces peers to proactively change their partners. Third, we develop RBCS, a resilient backbone, to mitigate DoS attacks on hybrid systems. Since a simulator for a fair evaluation is unavailable so far, we develop OSSim, a general-purpose simulation framework for P2P video streaming. Furthermore, we develop several attacker models and novel resilience metrics in OSSim. Extensive simulation studies show that the developed schemes significantly improve the resilient of pull-based and hybrid systems to both churn and DoS attacks.

This thesis is focused on the issue of violence in civil society. Using Charles Tilly's political theory, it attempts to point out that the emergence of collective violence can be well understood by tracing small scale causes (mechanisms), rather than large causes (poverty, extremism etc.). This argument is empirically studied in the context of anti-Roma riots that took place in Šluknov Hook, Czech republic, in the year 2011. The research is based on a broad concept of civil society, which doesn't assume fixed division between civil and uncivil subjects, but works with a number of actors, whose identity is unstable and their acting strategy fluently changes from nonviolent to violent and contra. The data show, that radical actors are generally more prone to use force. However, Tilly's theory provides opportunity to explain their influence on majority through the dynamics of relationships that is studied in this paper. The catalogue of events was created on the basis of news and document analysis and the incidence of theoretically defined mechanisms is identified by process tracing method: Boundary activation between us and them (mainly network-based escalation, signaling spirals), polarization, competitive display, selective retaliation, containment, monitoring, certification/decertification and...

Cyber attacks can target any nodes of the space infrastructure, and while these attacks are called non-violent, there is a credible capability to use cyber attacks to cause direct or indirect physical damage, injury or death. However, the vulnerability of satellites and other space assets to cyber attack is often overlooked, which is a significant failing given society's substantial and ever increasing reliance on satellite technologies. Through a policy analysis, this dissertation assess the set of political provisions provided by the European Union to address the cyber security issue of the space infrastructure. Such study aims at exploring the geopolitical consequences linked to space cyber security risks, and at assessing the political preparedness of the European Union to address these challenges. The perspective of transatlantic cooperation to further support both American and European effort to tackle this security risk is also addressed. The overarching value of the study is to contribute to future European cyber security for space and transatlantic debates by providing useful perspectives and key takeaways on these two domains. Ultimately, he existing set of policies are not sufficient to address the cyber security issue in Outer Space, a unified approach by the European Union and the United...

Ce travail s’appuie sur les études culturelles et historiques, la géopolitique, la narratologie, et la sémiologie de l’image pour étudier la guerre contre le terrorisme et ses représentations dans les séries télévisées américaines "24 heures chrono" et "Homeland". Produites à dix ans d’intervalle, ces deux fictions majeures de l’après-11 Septembre ont souvent été mises en opposition du fait de leur idéologie supposée, dans la lignée de la présidence républicaine de George W. Bush pour la première, de la présidence démocrate de Barack Obama pour la seconde. Cependant, l’on trouve de nombreuses ressemblances qui tendent non seulement à rapprocher "24" et "Homeland", mais également les présidences Bush et Obama. Notre travail consistera ainsi à mettre au jour l’ambivalence politique des deux programmes afin de s’interroger plus généralement sur les ruptures et les continuités de cette guerre mondiale contre le terrorisme que les États-Unis mènent depuis bientôt deux décennies. / This work uses cultural and historical studies, geopolitics, narratology, and visual semiotics to analyse the representations of the War on Terror in "24" and "Homeland", two emblematic post-9/11 American television series. These shows, which started airing almost a decade apart, have often been opposed to each other because of their presumed ideologies. Both dealing with the War on Terror, "24" has been said to reflect the conservatism of the Bush years, while "Homeland" would correspond to Obama’s liberal presidency. However, upon closer examination, many similarities can be found – which would not only bridge "24" and "Homeland", but also George W. Bush and Barack Obama’s presidencies. This work thus aims to deconstruct the preconceptions surrounding the two series by exploring their political ambivalence in order to question the ruptures and continuities in the global War on Terror which the United States has been conducting for almost twenty years now.

The aim of this thesis is to look for paralels in reactions and attitudes of Czech and American media towards offensive statements of presidents of the Czech Republic and USA with the focus on mainstream media. In a theoretical part of the thesis the role and function of media in liberal democracies are defined. Following part describes an actual media landscapes of USA and the Czech Republic. The main part - research, is based on the description of the media landscapes in both countries and analyzes the media reactions and attitudes towards one specific presidential statement (one by US president Donald Trump, one by Czech president Milos Zeman). Each statement had to be at most critical, attacking the media and had to raise high media response. Media reactions were afterwards analyzed using qualitative content analysis according to the principles of grounded theory. In the conclusion the categories given by the analysis are being compared and analyzed.

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