A Survey on Routing in Anonymous Communication Protocols

The Internet has undergone dramatic changes in the past 15 years, and now forms a global communication platform that billions of users rely on for their daily activities. While this transformation has brought tremendous benefits to society, it has also created new threats to online privacy, ranging from profiling of users for monetizing personal information to nearly omnipotent governmental surveillance. As a result, public interest in systems for anonymous communication has drastically increased. Several such systems have been proposed in the literature, each of which offers anonymity guarantees in different scenarios and under different assumptions, reflecting the plurality of approaches for how messages can be anonymously routed to their destination. Understanding this space of competing approaches with their different guarantees and assumptions is vital for users to understand the consequences of different design options. In this work, we survey previous research on designing, developing, and deploying systems for anonymous communication. To this end, we provide a taxonomy for clustering all prevalently considered approaches (including Mixnets, DC-nets, onion routing, and DHT-based protocols) with respect to their unique routing characteristics, deployability, and performance. This, in particular, encompasses the topological structure of the underlying network; the routing information that has to be made available to the initiator of the conversation; the underlying communication model; and performance-related indicators such as latency and communication layer. Our taxonomy and comparative assessment provide important insights about the differences between the existing classes of anonymous communication protocols, and it also helps to clarify the relationship between the routing characteristics of these protocols, and their performance and scalability

On service optimization in community network micro-clouds

Cotutela Universitat Politècnica de Catalunya i KTH Royal Institute of TechnologyInternet coverage in the world is still weak and local communities are required to come together and build their own network infrastructures. People collaborate for the common goal of accessing the Internet and cloud services by building Community networks (CNs). The use of Internet cloud services has grown over the last decade. Community network cloud infrastructures (i.e. micro-clouds) have been introduced to run services inside the network, without the need to consume them from the Internet. CN micro-clouds aims for not only an improved service performance, but also an entry point for an alternative to Internet cloud services in CNs. However, the adaptation of the services to be used in CN micro-clouds have their own challenges since the use of low-capacity devices and wireless connections without a central management is predominant in CNs. Further, large and irregular topology of the network, high software and hardware diversity and different service requirements in CNs, makes the CN micro-clouds a challenging environment to run local services, and to achieve service performance and quality similar to Internet cloud services. In this thesis, our main objective is the optimization of services (performance, quality) in CN micro-clouds, facilitating entrance to other services and motivating members to make use of CN micro-cloud services as an alternative to Internet services. We present an approach to handle services in CN micro-cloud environments in order to improve service performance and quality that can be approximated to Internet services, while also giving to the community motivation to use CN micro-cloud services. Furthermore, we break the problem into different levels (resource, service and middleware), propose a model that provides improvements for each level and contribute with information that helps to support the improvements (in terms of service performance and quality) in the other levels. At the resource level, we facilitate the use of community devices by utilizing virtualization techniques that isolate and manage CN micro-cloud services in order to have a multi-purpose environment that fosters services in the CN micro-cloud environment. At the service level, we build a monitoring tool tailored for CN micro-clouds that helps us to analyze service behavior and performance in CN micro-clouds. Subsequently, the information gathered enables adaptation of the services to the environment in order to improve their quality and performance under CN environments. At the middleware level, we build overlay networks as the main communication system according to the social information in order to improve paths and routes of the nodes, and improve transmission of data across the network by utilizing the relationships already established in the social network or community of practices that are related to the CNs. Therefore, service performance in CN micro-clouds can become more stable with respect to resource usage, performance and user perceived quality.Acceder a Internet sigue siendo un reto en muchas partes del mundo y las comunidades locales se ven en la necesidad de colaborar para construir sus propias infraestructuras de red. Los usuarios colaboran por el objetivo común de acceder a Internet y a los servicios en la nube construyendo redes comunitarias (RC). El uso de servicios de Internet en la nube ha crecido durante la última década. Las infraestructuras de nube en redes comunitarias (i.e., micronubes) han aparecido para albergar servicios dentro de las mismas redes, sin tener que acceder a Internet para usarlos. Las micronubes de las RC no solo tienen por objetivo ofrecer un mejor rendimiento, sino también ser la puerta de entrada en las RC hacia una alternativa a los servicios de Internet en la nube. Sin embargo, la adaptación de los servicios para ser usados en micronubes de RC conlleva sus retos ya que el uso de dispositivos de recursos limitados y de conexiones inalámbricas sin una gestión centralizada predominan en las RC. Más aún, la amplia e irregular topología de la red, la diversidad en el hardware y el software y los diferentes requisitos de los servicios en RC convierten en un desafío albergar servicios locales en micronubes de RC y obtener un rendimiento y una calidad del servicio comparables a los servicios de Internet en la nube. Esta tesis tiene por objetivo la optimización de servicios (rendimiento, calidad) en micronubes de RC, facilitando la entrada a otros servicios y motivando a sus miembros a usar los servicios en la micronube de RC como una alternativa a los servicios en Internet. Presentamos una aproximación para gestionar los servicios en entornos de micronube de RC para mejorar su rendimiento y calidad comparable a los servicios en Internet, a la vez que proporcionamos a la comunidad motivación para usar los servicios de micronube en RC. Además, dividimos el problema en distintos niveles (recursos, servicios y middleware), proponemos un modelo que proporciona mejoras para cada nivel y contribuye con información que apoya las mejoras (en términos de rendimiento y calidad de los servicios) en los otros niveles. En el nivel de los recursos, facilitamos el uso de dispositivos comunitarios al emplear técnicas de virtualización que aíslan y gestionan los servicios en micronubes de RC para obtener un entorno multipropósito que fomenta los servicios en el entorno de micronube de RC. En el nivel de servicio, construimos una herramienta de monitorización a la medida de las micronubes de RC que nos ayuda a analizar el comportamiento de los servicios y su rendimiento en micronubes de RC. Luego, la información recopilada permite adaptar los servicios al entorno para mejorar su calidad y rendimiento bajo las condiciones de una RC. En el nivel de middleware, construimos redes de overlay que actúan como el sistema de comunicación principal de acuerdo a información social para mejorar los caminos y las rutas de los nodos y mejoramos la transmisión de datos a lo largo de la red al utilizar las relaciones preestablecidas en la red social o la comunidad de prácticas que están relacionadas con las RC. De este modo, el rendimiento en las micronubes de RC puede devenir más estable respecto al uso de recursos, el rendimiento y la calidad percibidas por el usuario.Postprint (published version

A Survey on Routing in Anonymous Communication Protocols

The Internet has undergone dramatic changes in the past 2 decades and now forms a global communication platform that billions of users rely on for their daily activities. While this transformation has brought tremendous benefits to society, it has also created new threats to online privacy, such as omnipotent governmental surveillance. As a result, public interest in systems for anonymous communication has drastically increased. In this work, we survey previous research on designing, developing, and deploying systems for anonymous communication. Our taxonomy and comparative assessment provide important insights about the differences between the existing classes of anonymous communication protocols

Increasing Structured P2P Protocol Resilience to Localized Attacks

The Peer-to-Peer (P2P) computing model has been applied to many application fields over the last decade. P2P protocols made their way from infamous - and frequently illicit - file sharing applications towards serious applications, e.g., in entertainment, audio/video conferencing, or critical applications like smart grid, Car-2-Car communication, or Machine-to-Machine communication. Some of the reasons for that are P2P's decentralized design that inherently provides for fault tolerance to non-malicious faults. However, the base P2P scalability and decentralization requirements often result in design choices that negatively impact their robustness to varied security threats. A prominent vulnerability are Eclipse attacks (EA) that aim at information hiding and consequently perturb a P2P overlay's reliable service delivery. This dissertation provides the necessary background to understand the different types and inherent complexity of EAs, the susceptibility of many P2P protocols to EAs, and a mitigation technique for the localized EA variant. The applicability of the proposed mitigation technique has been validated experimentally and shows for a wide range of system parameters and application scenarios good mitigation rates reaching up to 100%

Enhancing System Transparency, Trust, and Privacy with Internet Measurement

While on the Internet, users participate in many systems designed to protect their information’s security. Protection of the user’s information can depend on several technical properties, including transparency, trust, and privacy. Preserving these properties is challenging due to the scale and distributed nature of the Internet; no single actor has control over these features. Instead, the systems are designed to provide them, even in the face of attackers. However, it is possible to utilize Internet measurement to better defend transparency, trust, and privacy. Internet measurement allows observation of many behaviors of distributed, Internet-connected systems. These new observations can be used to better defend the system they measure. In this dissertation, I explore four contexts in which Internet measurement can be used to the aid of end-users in Internet-centric, adversarial settings. First, I improve transparency into Internet censorship practices by developing new Internet measurement techniques. Then, I use Internet measurement to enable the deployment of end-to-middle censorship circumvention techniques to a half-million users. Next, I evaluate transparency and improve trust in the Web public-key infrastructure by combining Internet measurement techniques and using them to augment core components of the Web public-key infrastructure. Finally, I evaluate browser extensions that provide privacy to users on the web, providing insight for designers and simple recommendations for end-users. By focusing on end-user concerns in widely deployed systems critical to end-user security and privacy, Internet measurement enables improvements to transparency, trust, and privacy.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163199/1/benvds_1.pd

Acetylcholine in Central Cardiorespiratory Regulation in Health and Depression

Circulation and breathing movements that are essential for life are regulated by neurons in the hypothalamus and lower brainstem. Activity of these neurons is regulated by peripheral afferent and higher order inputs that release a diverse array of amino acids, amines and peptides. In this thesis we investigated the role of the neurotransmitter acetylcholine (ACh) and its receptors in regulation of cardiorespiratory homeostasis. Secondly, we determined whether or not genetic disturbances in regulation of acetylcholine receptor sensitivity affect central control of circulation, body temperature or respiration. The findings presented in Chapter 3 reveal a novel functional role of ACh and G-protein coupled muscarinic receptor (mAChR) activation in the rostral ventrolateral medulla (RVLM). We showed for the first time that some non-C1 RVLM neurons express mRNA for the M2 or M3 receptor; however, both C1 and enkephalinergic RVLM neurons were closely apposed by c holinergic terminals positive for the vesicular acetylcholine transporter (vAChT). Physiological studies demonstrated that activation of mAChR within the RVLM in anaesthetised rats increases arterial pressure and sympathetic nerve activity and has differential effects on major cardiorespiratory reflexes: RVLM mAChR activation resets the sympathetic baroreflex to higher arterial pressures and increases its gain and, concomitantly, attenuates excitatory reflexes evoked by peripheral chemoreceptor or somatic afferent stimulation. Retrograde tracing from the RVLM combined with vAChT immunoreactivity showed that neurons in the pedunculopontine tegmental nucleus (PPT) are the sole source of cholinergic input to the RVLM. The PPT-RVLM pathway appears to be part of a central command circuit concerned with adjusting circulatory function appropriate to increased muscle activity. These data support the notion that activation of specific neurotransmitter receptors in the RVLM encodes fu nctional specificity in control of sympathetic outflow and r! eflex fu nction. The extent to which genetic variations in central mAChR sensitivity influence autonomic function is unknown. Flinders Sensitive Line (FSL) rats were bred from Sprague Dawley (SD) rats for exaggerated behavioural and hypothermic responses to cholinesterase inhibitors and direct-acting mAChR agonists. A control genetic counterpart, the Flinders Resistant Line (FRL), was also bred in parallel for reduced responses to cholinergic agonists. The findings of Chapter 5 showed for the first time that FSL rats exhibit an increase in M2 and reduction in M3 receptor expression in the rostral medulla, suggesting that cholinergic signalling in this region may be altered. However, alterations of mAChR expression specific to FSL rats were restricted to this area and there were no changes in cerebellar expression of mAChR in any strain. Physiological studies showed that conscious or anaesthetised FSL rats were more sensitive to thermoregulatory responses to central mAChR a ctivation (ie hypothermia and increase in cutaneous blood flow); whereas pressor responses were reduced compared to SD and FRL rats. The increase in sympathetic activity and depression of respiration evoked by central mAChR activation was unchanged and attenuated, respectively, in FSL rats compared to control strains. These findings indicate that mAChR involved in control of different autonomic functions are regulated independently at the genetic and / or post-transcriptional level. The findings of Chapters 4 and 6 reveal a novel effect of breeding for cholinergic hypersensitivity in FSL rats on control of vagal and sympathetic outflow. Spectral analysis of blood pressure recordings in conscious FSL rats showed a reduction in total and high frequency power of heart rate variability (HRV), an increase in the LF/HF ratio and reduction in baroreflex sensitivity (BRS) compared to controls. These changes reflect a reduction in reflex vagal input and relative predominan ce of sympathetic input to the sinus node in FSL rats. Under! urethan e anaesthesia, FSL rats had a higher heart rate and exhibited lower gain of baroreflex control of splanchnic sympathetic nerve activity (SNA). Moreover, FSL rats were more susceptible to ventricular arrhythmias during infusion of the cardiac glycoside ouabain under anaesthesia compared to controls. These data indicate that FSL rats exhibit impaired reflex regulation of vagal and sympathetic outflow that could underlie increased vulnerability to arrhythmia seen in this strain. The precise brain regions and neurotransmitters that underlie autonomic disturbances seen in FSL rats are unclear. As well as muscarinic hypersensitivity, FSL rats also exhibit increased sensitivity to nicotine, serotonin and dopamine. Multiple chemical sensitivities in FSL rats may arise from functional interactions with mAChR or changes in common intracellular regulatory or signalling pathways. FSL rats exhibit a number of behavioural and somatic abnormalities consistent with clinical depre ssion, including reduced motivated behaviour and sleep and psychomotor disturbances. These symptoms are also alleviated by treatment with antidepressants, suggesting that similar neurochemical abnormalities may underlie behavioural disturbances seen in FSL rats and human depression. Symptoms of depression are an emerging risk factor in the development of cardiovascular disease and are associated with increased risk of dying from a cardiac-related event. A reduction in HRV and BRS in depressed patients has been widely reported and is considered to be a key substrate predisposing to arrhythmia in this patient group. In this thesis we demonstrate for the first time that FSL rats exhibit similar autonomic abnormalities to those reported in human depression and are more vulnerable to ouabain-induced ventricular arrhythmias. These findings suggest that biological factors predisposing to autonomic dysfunction and arrhythmia in FSL rats could also operate in human depression. This m ay involve altered neurotransmission in cardiovascular brain! regions , or inappropriate regulation of cardiovascular function by arousal or motor control pathways. Overall, this thesis provides novel insights into cholinergic mechanisms that regulate cardiorespiratory homeostasis. ACh is important in physiological regulation of circulation via activation of G-protein coupled mAChR in the RVLM. Selective breeding for cholinergic hypersensitivity in FSL and FRL rats results in region- and subtype-specific changes in mAChR expression in the lower brainstem and differentially influences muscarinic control of circulation and breathing. Variations in central mAChR sensitivity may contribute to impaired reflex control of vagal and sympathetic outflow and could hence predispose to cardiac complications including arrhythmias. Future studies may aim to further understand the relationship between endogenous sensitivity of metabotropic neurotransmitter receptors in the CNS and cardiovascular disturbances associated with depression

Posters-at-the-Capitol 2017 Program Booklet

Posters-at-the-Capitol 2017 Program Booklet Contents: Welcoming Remarks Posters-at-the-Capitol Organizing Committee Welcome Letter from Mr. Robert King Schedule of Activities Mezzanine Map Participant Listings Eastern Kentucky University Kentucky State University Kentucky Community & Technical College System Morehead State University Murray State University Northern Kentucky University University of Louisville University of Kentucky Western Kentucky University Programs of Distinction Student Abstract

Defending networked resources against floods of unwelcome requests

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2008.Includes bibliographical references (p. 172-189).The Internet is afflicted by "unwelcome requests'" defined broadly as spurious claims on scarce resources. For example, the CPU and other resources at a server are targets of denial-of-service (DOS) attacks. Another example is spam (i.e., unsolicited bulk email); here, the resource is human attention. Absent any defense, a very small number of attackers can claim a very large fraction of the scarce resources. Traditional responses identify "bad" requests based on content (for example, spam filters analyze email text and embedded URLs). We argue that such approaches are inherently gameable because motivated attackers can make "bad" requests look "good". Instead, defenses should aim to allocate resources proportionally (so if lo% of the requesters are "bad", they should be limited to lo% of the scarce resources). To meet this goal, we present the design, implementation, analysis, and experimental evaluation of two systems. The first, speak-up, defends servers against application-level denial-of-service by encouraging all clients to automatically send more traffic. The "good" clients can thereby compete equally with the "bad" ones. Experiments with an implementation of speak-up indicate that it allocates a server's resources in rough proportion to clients' upload bandwidths, which is the intended result. The second system, DQE, controls spam with per-sender email quotas. Under DQE, senders attach stamps to emails. Receivers communicate with a well-known, untrusted enforcer to verify that stamps are fresh and to cancel stamps to prevent reuse. The enforcer is distributed over multiple hosts and is designed to tolerate arbitrary faults in these hosts, resist various attacks, and handle hundreds of billions of messages daily (two or three million stamp checks per second). Our experimental results suggest that our implementation can meet these goals with only a few thousand PCs.(cont) The enforcer occupies a novel design point: a set of hosts implement a simple storage abstraction but avoid neighbor maintenance, replica maintenance, and mutual trust. One connection between these systems is that DQE needs a DoS defense-and can use speak-up. We reflect on this connection, on why we apply speak-up to DoS and DQE to spam, and, more generally, on what problems call for which solutions.by Michael Walfish.Ph.D