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Reti acustiche sottomarine: progettazione di protocolli e problematiche di sicurezza
Get PDFNonostante le reti sottomarine siano ormai studiate da tempo, esistono an- cora molte difficolt`a da affrontare, causate dell’avversit`a del canale acustico, per poter stabilire una comunicazione wireless affidabile. Inoltre, lo sviluppo di nuovi modem a basso costo apre la strada a nuove applicazioni per le reti sottomarine, come, ad esempio, applicazioni per i futuri porti intelligenti. Ad oggi, comunque, i principali ambiti di utilizzo delle reti sottomarine ri- mangono quello militare e di pubblica sicurezza, la cui rilevanza pone inoltre ulteriori sfide legate anche alla sicurezza delle reti. Infatti, un’interruzione dei servizi forniti dalle reti causata da un attacco potrebbe portare a se- rie conseguenze. Tuttavia fino ad ora, gli aspetti di sicurezza delle reti sottomarine non sono stati adeguatamente studiati e l’utilizzo di contro- misure progettate per reti terrestri non sempre risulta possibile. In questa tesi ci occuperemo sia della progettazione di protocolli di comunicazione efficaci, che dell’analisi di attacchi e contromisure nelle reti sottomarine. Prima di tutto, progetteremo un protocollo MAC per la raccolta di dati da sensori sottomarini in ambiente portuale e analizzeremo le prestazioni com- plessive della rete, dalla trasmissione dei dati dai sensori fino alla ricezione sulla costa. L’analisi delle prestazioni verr`a effettuata sia attraverso sim- ulazioni che attraverso test sperimentali. Successivamente, ci dedicheremo all’analisi della sicurezza nelle reti sottomarine. Cominceremo analizzando degli scenari in cui gli attaccanti dispongono di una conoscenza limitata dei protocolli di rete, studiando gli effetti di attacchi di tipo jamming e re- play. Progetteremo, poi, contromisure basate sulla reputazione di un nodo, a protezione di attacchi piu` sofisticati in cui il nodo attaccante conosce il funzionamento e le vulnerabilit`a dei protocolli e sfrutta queste conoscenze per attaccare la rete. In entrambi i casi, ci concentreremo sulle peculiarit`a delle comunicazioni acustiche che rendono gli attacchi e le contromisure differenti rispetto a quelli in ambito terrestre.Although underwater networks have been developed for considerable time now, the harshness of the acoustic channel still poses a lot of challenges for wireless communications. In addition, the development of low cost modems paves the way for new applications in different scenarios, such as future smart ports. Nevertheless, for the time being, the use of underwater net- works is still mainly related to military and public safety applications, whose relevance arises further challenges related also to network security. Indeed, a network failure caused by an attack could lead to serious consequences. However, security problems have not been deeply investigated so far, and the implementation of terrestrial network countermeasures in the underwater field is not always feasible. In this thesis we focus on both open challenges previously described: the design of efficient communication protocols, and the analysis of attacks and countermeasures in underwater networks. First, we consider a data collection service in a smart port scenario, designing a Medium Access Control (MAC) protocol for this service and analyzing the End-To-End (E2E) transmission, from sensor nodes to the shore. We eval- uate the performance through both simulations and field tests. Afterward, we analyze security issues in underwater networks. We start by analyzing attackers with limited knowledge of the protocol stack, studying the effect of jamming and replay attacks. We then move to the design of a counter- measure based on a trust metric to be employed against more sophisticated attacks in which the malicious node can exploit the protocol’s behavior and vulnerabilities to carry out the attacks. In both cases we specifically focus on the peculiarities of the acoustic channel that differentiate attacks and countermeasures in underwater networks from their terrestrial counterpart
A Game-Theoretic and Experimental Analysis of Energy-Depleting Underwater Jamming Attacks
No full textSecurity aspects in underwater wireless networks have not been widely investigated so far, despite the critical importance of the scenarios in which these networks can be employed. For example, an attack to a military underwater network for enemy targeting or identification can lead to serious consequences. Similarly, environmental monitoring applications such as tsunami prevention are also critical from a public safety point of view. In this work, we assess a scenario in which a malicious node tries to perform a jamming attack, degrading the communication quality of battery-powered underwater nodes. The legitimate transmitter may use packet level coding to increase the chances of correctly delivering packets. Because of the energy limitation of the nodes, the jammer’s objective is twofold, namely: (i) disrupting the communication and (ii) reducing the lifetime of the victim by making it send more redundancy. We model the jammer and the transmitter as players in a multistage game, deriving the optimal strategies. We evaluate the performance both in a model-based scenario and using real experimental data, and perform a sensitivity analysis to evaluate the performance of the strategies if the real channel model is different from the one they use
Modeling the performance of optical modems in the DESERT underwater network simulator
No full textWhile in the past decades only low rate acoustic modems were employed for underwater wireless communication, nowadays also high rate optical modems can be used for short range communication, up to a few hundred meters. A key ques- tion is what is the expected performance of a modem in a given scenario, in order to predict the coverage range of the system in a network deployment. In the literature, many models have been proposed, but each of them is limited to simulating a particular device or a limited set of scenarios. However, in the last decade, many sea evaluations of optical communications performance in different water conditions have been performed, and many datasets published and presented to the research community. In this paper we collect a database of performance figures of optical modems, including it in the DESERT Underwater network simulator. In addition, we simulate optical communication in a real scenario, thanks to the water measurements retrieved during the ALOMEX'15 NATO cruise
Multi-hop range extension of a wireless remote control for underwater vehicles
No full textIn this paper, we explore the feasibility of controlling an Underwater Autonomous Vehicle (AUV) from a base station, via a multi-hop wireless control channel. As a first step, we identify which networking and data-link protocols can be employed in this system. Then, we design a simple but effective routing protocol for this scenario. Finally, we simulate the performance of the system during missions of interest, and conclude by discussing the effectiveness of wireless multi-hop control methods for AUVs
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
AUVs Telemetry Range Extension through a Multimodal Underwater Acoustic Network
No full textIn this paper, we describe an underwater multi-hop network scenario based only on acoustic modems operating at different frequencies. The idea is to remotely control an Autonomous Underwater Vehicle (AUV) and verify whether it is able to follow the path sent by a control station (CTR) in the form of consecutive waypoints. The AUV sends back packets that can be monitoring or control information. We tested by simulation different MAC layer protocols to compare their performance in terms of throughput and packet delivery delay, in particular focusing on both contention-free (TDMA-based) and contention-based (CSMA-based) protocols, to analyze which solution performs better in different network conditions varying the amount of traffic generated by the AUV during its mission
Underwater Jamming Attacks as Incomplete Information Games
No full textAutonomous Underwater Vehicles (AUVs) have several fundamental civilian and military applications, and Denial of Service (DoS) attacks against their communications are a serious threat. In this work, we analyze such an attack using game theory in an asymmetric scenario, in which the node under attack does not know the position of the jammer that blocks its signals. The jammer has a dual objective, namely, disrupting communications and forcing the legitimate transmitter to spend more energy protecting its own transmissions. Our model shows that, if both nodes act rationally, the transmitter is able to quickly reduce its disadvantage, estimating the location of the jammer and responding optimally to the attack
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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