Security in DHT-based peer-to-peer networks

Questa tesi riguarda il problema dell’integrazione dei meccanismi per la gestione di reputazione e dei processi di lookup nelle reti peer-to-peer basate su DHT (Distributed Hash Table) e l’applicazione di tali tecniche a scenari di reti chiuse e gerarchiche con particolare riferimento al livello di sicurezza e efficienza dello storage e del backup delle risorse. La soluzione proposta rappresenta una combinazione delle tecniche per la valutazione di reputazione e degli strumenti per i sistemi di computer distribuiti come protezione dagli specifici attacchi causati dai peer maliziosi in sistemi P2P collaborativi. Inoltre, e’ stata proposta l’applicazione dei meccanismi DHT nell’ambito delle reti di computer gerarchiche, in particolare nelle reti aziendali. L’obiettivo di questo lavoro e’ quello di offrire una soluzione ai problemi derivanti dall’utilizzo di una architettura centralizzata tramite l’introduzione del sistema di organizzazione dei dati inerente all’ambito P2P basato sugli algoritmi DHT in una rete aziendale.This thesis addresses the problem of integration of reputation management mechanisms and other instruments used in distributed computing environment with lookup processes in DHT-based peer-to-peer networks in order to improve resilience of such systems to destructive actions of malevolent or faulty components. The goal of this integration is to obtain a more efficient, less expensive (in terms of data transferred, computational resources involved and time spent) and possibly simple solution to cope with the specific problems of DHT-based environment. A particular accent has been given to DHT-based environments with a collaborative nature. Another issue considered in this work regards the application of DHT mechanisms to lookup and data retrieval processes in hierarchical collaborative environments, in particular, in enterprise networks. This approach exploits advantages of the P2P data organization system based on DHTs to avoid some problems inherent in systems with centralized architectures

Byzantine Agreement for Reputation Management in DHT-based Peer-to-Peer Networks

DHT-based peer-to-peer networks represent a particular environment with specific security problems. Some types of malicious activity in this kind of networks can cause the same problems as Byzantine failure in distributed computer systems. In this work we propose to integrate solutions for Byzantine Agreement (BA) used in distributed computing environment and reputation mechanisms designed for P2P networks based on DHTs, in order to obtain a simpler and efficient algorithm for reputation management. We present the complexity evaluation of the proposed solution compared to a previous reputation algorithm for DHT-based networks in terms of number of messages sent per node. The results of this evaluation show that the algorithm we present here is less "expensive" in both number of messages sent and computational and memory resources involved at an adequate participation level of each network node