SW-V: modelo de streaming de software baseado em técnicas de virtualização e transporte peer-to-peer

Pós-graduação em Ciência da Computação - IBILCE

Modelo estrutural para compartilhamento de arquivos peer-to-peer

Pós-graduação em Ciência da Computação - IBILCE

Evolutionary methods for self-organizing cooperation in peer-to-peer networks

The Peer-to-Peer network paradigm is drawing the attention of both final users and researchers for its features. P2P networks shift from the classic client-server approach to a high level of decentralization where there is no central control and all the nodes should be able not only to require services, but to provide them to other peers as well. While on one hand such high level of decentralization might lead to interesting properties like scalability and fault tolerance, on the other hand it implies many new problems to deal with. A key feature of many P2P systems is openness, meaning that everybody is potentially able to join a network with no need for subscription or payment systems. The combination of openness and lack of central control makes it feasible for a user to free-ride, that is to increase its own benefit by using services without allocating resources to satisfy other peers’ requests. One of the main goals when designing a P2P system is therefore to achieve cooperation between users. Given the nature of P2P systems based on simple local interactions of many peers having partial knowledge of the whole system, an interesting way to achieve desired properties on a system scale might consist in obtaining them as emergent properties of the many interactions occurring at local node level. Two methods are typically used to face the problem of cooperation in P2P networks: 1) engineering emergent properties when designing the protocol; 2) study the system as a game and apply Game Theory techniques, especially to find Nash Equilibria in the game and to reach them making the system stable against possible deviant behaviors. In this work we present an evolutionary framework to enforce cooperative behaviour in P2P networks that is alternative to both the methods mentioned above. Our approach is based on an evolutionary algorithm inspired by computational sociology and evolutionary game theory, consisting in having each peer periodically trying to copy another peer which is performing better. The proposed algorithms, called SLAC and SLACER, draw inspiration from tag systems originated in computational sociology, the main idea behind the algorithm consists in having low performance nodes copying high performance ones. The algorithm is run locally by every node and leads to an evolution of the network both from the topology and from the nodes’ strategy point of view. Initial tests with a simple Prisoners’ Dilemma application show how SLAC is able to bring the network to a state of high cooperation independently from the initial network conditions. Interesting results are obtained when studying the effect of cheating nodes on SLAC algorithm. In fact in some cases selfish nodes rationally exploiting the system for their own benefit can actually improve system performance from the cooperation formation point of view. The final step is to apply our results to more realistic scenarios. We put our efforts in studying and improving the BitTorrent protocol. BitTorrent was chosen not only for its popularity but because it has many points in common with SLAC and SLACER algorithms, ranging from the game theoretical inspiration (tit-for-tat-like mechanism) to the swarms topology. We discovered fairness, meant as ratio between uploaded and downloaded data, to be a weakness of the original BitTorrent protocol and we drew inspiration from the knowledge of cooperation formation and maintenance mechanism derived from the development and analysis of SLAC and SLACER, to improve fairness and tackle freeriding and cheating in BitTorrent. We produced an extension of BitTorrent called BitFair that has been evaluated through simulation and has shown the abilities of enforcing fairness and tackling free-riding and cheating nodes.

Streaming audio e video nei sistemi Peer-To-Peer TV: il caso Sopcast P2PTV

La tesi si propone di affrontare il tema del Live Streaming in sistemi P2P con particolare riferimento a Sopcast, un applicativo di P2PTV. Viene fatto un ricorso storico riguardo alla nascita dello streaming e al suo sviluppo, vengono descritte le caratteristiche, il protocollo di comunicazione e i modelli più diffusi per il live streaming P2P. Inoltre si tratterà come viene garantita la qualità del servizio e valutate le performance di un servizio P2PTV.

Composizione musicale e streaming peer-to-peer con web audio e webrtc

La tesi descrive lo sviluppo di un'applicazione web per comporre musica tramite la tecnica del "live looping" che fornisce anche la possibilità di effettuare lo streaming di ciò che si crea in tempo reale e in maniera peer-to-peer. L'applicazione in oggetto (chiamata WebLooper) fa uso di due tecnologie web emergenti in ambito multimediale: Web Audio e WebRTC, attualmente in attesa di diventare standard W3C.

Architettura di supporto al peer-to-peer gaming basata su network coding

La popolarita` dei giochi online e` in crescita, ma allo stesso tempo le architetture proposte dagli sviluppatori e le connessioni di cui sono dotati gli utenti sembrano restare non adeguate a questo. Nella tesi si descrive un'architettura peer-to-peer che riesce ad effettuare una riduzione nella perdita dei pacchetti grazie al meccanismo del Network Coding senza effetti collaterali per la latenza.

Indagini forensi in tema di scambio di file pedopornografici mediante software di file sharing a mezzo peer-to-peer

La prova informatica richiede l’adozione di precauzioni come in un qualsiasi altro accertamento scientifico. Si fornisce una panoramica sugli aspetti metodologici e applicativi dell’informatica forense alla luce del recente standard ISO/IEC 27037:2012 in tema di trattamento del reperto informatico nelle fasi di identificazione, raccolta, acquisizione e conservazione del dato digitale. Tali metodologie si attengono scrupolosamente alle esigenze di integrità e autenticità richieste dalle norme in materia di informatica forense, in particolare della Legge 48/2008 di ratifica della Convenzione di Budapest sul Cybercrime. In merito al reato di pedopornografia si offre una rassegna della normativa comunitaria e nazionale, ponendo l’enfasi sugli aspetti rilevanti ai fini dell’analisi forense. Rilevato che il file sharing su reti peer-to-peer è il canale sul quale maggiormente si concentra lo scambio di materiale illecito, si fornisce una panoramica dei protocolli e dei sistemi maggiormente diffusi, ponendo enfasi sulla rete eDonkey e il software eMule che trovano ampia diffusione tra gli utenti italiani. Si accenna alle problematiche che si incontrano nelle attività di indagine e di repressione del fenomeno, di competenza delle forze di polizia, per poi concentrarsi e fornire il contributo rilevante in tema di analisi forensi di sistemi informatici sequestrati a soggetti indagati (o imputati) di reato di pedopornografia: la progettazione e l’implementazione di eMuleForensic consente di svolgere in maniera estremamente precisa e rapida le operazioni di analisi degli eventi che si verificano utilizzando il software di file sharing eMule; il software è disponibile sia in rete all’url http://www.emuleforensic.com, sia come tool all’interno della distribuzione forense DEFT. Infine si fornisce una proposta di protocollo operativo per l’analisi forense di sistemi informatici coinvolti in indagini forensi di pedopornografia.

La crittografia nel sistema di moneta digitale Bitcoin

In questo documento si presenta lo studio degli algoritmi matematici e crittografici su cui si basa il sistema di moneta digitale Bitcoin, in circolazione dal 2009. Bitcoin è un sistema di cripto valuta elettronica peer-to-peer, ideato da un anonimo conosciuto con lo pseudonimo "Satoshi Nakamoto", i cui principi sono descritti in un documento pubblicato nel 2008 ed ora accessibile in rete. L'utilizzo di Bitcoin permette di effettuare transazioni con sicurezza da un soggetto ad un altro e, grazie a una tecnologia peer-to-peer che opera senza alcuna autorità centrale e intermediari quali banche o istituzioni governative, sia la gestione delle operazioni sia l'emissione di denaro sono svolte per mezzo di un protocollo P2P. Nel corso della trattazione si propone un analisi più tecnica del sistema di gestione e creazione dei Bitcoin e degli strumenti crittografici che hanno permesso l'avvento di questa moneta elettronica decentralizzata.

Design and implementation of an anonymous peer-to-peer iaas cloud

Cloud services are becoming ever more important for everyone's life. Cloud storage? Web mails? Yes, we don't need to be working in big IT companies to be surrounded by cloud services. Another thing that's growing in importance, or at least that should be considered ever more important, is the concept of privacy. The more we rely on services of which we know close to nothing about, the more we should be worried about our privacy. In this work, I will analyze a prototype software based on a peer to peer architecture for the offering of cloud services, to see if it's possible to make it completely anonymous, meaning that not only the users using it will be anonymous, but also the Peers composing it will not know the real identity of each others. To make it possible, I will make use of anonymizing networks like Tor. I will start by studying the state of art of Cloud Computing, by looking at some real example, followed by analyzing the architecture of the prototype, trying to expose the differences between its distributed nature and the somehow centralized solutions offered by the famous vendors. After that, I will get as deep as possible into the working principle of the anonymizing networks, because they are not something that can just be 'applied' mindlessly. Some de-anonymizing techniques are very subtle so things must be studied carefully. I will then implement the required changes, and test the new anonymized prototype to see how its performances differ from those of the standard one. The prototype will be run on many machines, orchestrated by a tester script that will automatically start, stop and do all the required API calls. As to where to find all these machines, I will make use of Amazon EC2 cloud services and their on-demand instances.

Disseminazioni in reti peer-to-peer attraverso algoritmi di gossip a due fasi

Gli algoritmi di gossip sono utilizzati per la disseminazione di messaggi in una rete peer-to-peer. La tesi tratta lo sviluppo, l'implementazione e l'analisi di quattro nuovi algoritmi di gossip "a due fasi". Gli algoritmi sono stati sviluppati e testati con il simulatore LUNES per poi essere analizzati in vari confronti con gli algoritmi classici dell'ambito, ovvero Fixed Probability e Conditional Broadcast. Le prove sono state effettuate su varie tipologie di grafi, ovvero Random, Scale-free, Small-world e K-Regular.

Bringing results to fruition through publication: An analysis of a peer-reviewed, open access and context-focused journal's editorial practice

When it comes to helping to shape sustainable development, research is most useful when it bridges the science–implementation/management gap and when it brings development specialists and researchers into a dialogue (Hurni et al. 2004); can a peer-reviewed journal contribute to this aim? In the classical system for validation and dissemination of scientific knowledge, journals focus on knowledge exchange within the academic community and do not specifically address a ‘life-world audience’. Within a North-South context, another knowledge divide is added: the peer review process excludes a large proportion of scientists from the South from participating in the production of scientific knowledge (Karlsson et al. 2007). Mountain Research and Development (MRD) is a journal whose mission is based on an editorial strategy to build the bridge between research and development and ensure that authors from the global South have access to knowledge production, ultimately with a view to supporting sustainable development in mountains. In doing so, MRD faces a number of challenges that we would like to discuss with the td-net community, after having presented our experience and strategy as editors of this journal. MRD was launched in 1981 by mountain researchers who wanted mountains to be included in the 1992 Rio process. In the late 1990s, MRD realized that the journal needed to go beyond addressing only the scientific community. It therefore launched a new section addressing a broader audience in 2000, with the aim of disseminating insights into, and recommendations for, the implementation of sustainable development in mountains. In 2006, we conducted a survey among MRD’s authors, reviewers, and readers (Wymann et al. 2007): respondents confirmed that MRD had succeeded in bridging the gap between research and development. But we realized that MRD could become an even more efficient tool for sustainability if development knowledge were validated: in 2009, we began submitting ‘development’ papers (‘transformation knowledge’) to external peer review of a kind different from the scientific-only peer review (for ‘systems knowledge’). At the same time, the journal became open access in order to increase the permeability between science and society, and ensure greater access for readers and authors in the South. We are currently rethinking our review process for development papers, with a view to creating more space for communication between science and society, and enhancing the co-production of knowledge (Roux 2008). Hopefully, these efforts will also contribute to the urgent debate on the ‘publication culture’ needed in transdisciplinary research (Kueffer et al. 2007).