Prêt entre particuliers | EPFL Graph Search

Le prêt entre particuliers, également crédit communautaire (en anglais peer-to-peer lending, P2P lending ou parfois aussi social lending) est une activité financière qui consiste en des prêts d'argent entre particuliers, sous la forme de remise de fonds avec engagement de remboursement. Ce système proche de celui du microcrédit développé par Muhammad Yunus, prix Nobel de la paix, a pour but de permettre à toute personne désireuse de prêter ou d’emprunter de le faire directement entre particuliers, avec ou sans intermédiaires bancaires. La simplicité de ce système permet à toute personne de rechercher un crédit sans passer par les établissements de crédit (les banques) ou par les organismes de crédit. Principes Ce circuit de création et de distribution de crédits repose sur le prêt direct de particulier à particulier (peer-to-peer). L'objectif consiste à réduire le coût de distribution, élevé dans la banque, et à disposer d'une analyse différente du risque. L'emprunteur

High Quality P2P Service Provisioning via Decentralized Trust Management

Hung Le Vu

Trust management is essential to fostering cooperation and high quality service provisioning in several peer-to-peer (P2P) applications. Among those applications are customer-to-customer (C2C) trading sites and markets of services implemented on top of centralized infrastructures, P2P systems, or online social networks. Under these application contexts, existing work does not adequately address the heterogeneity of the problem settings in practice. This heterogeneity includes the different approaches employed by the participants to evaluate trustworthiness of their partners, the diversity in contextual factors that influence service provisioning quality, as well as the variety of possible behavioral patterns of the participants. This thesis presents the design and usage of appropriate computational trust models to enforce cooperation and ensure high quality P2P service provisioning, considering the above heterogeneity issues. In this thesis, first I will propose a graphical probabilistic framework for peers to model and evaluate trustworthiness of the others in a highly heterogeneous setting. The framework targets many important issues in trust research literature: the multi-dimensionality of trust, the reliability of different rating sources, and the personalized modeling and computation of trust in a participant based on the quality of services it provides. Next, an analysis on the effective usage of computational trust models in environments where participants exhibit various behaviors, e.g., honest, rational, and malicious, will be presented. I provide theoretical results showing the conditions under which cooperation emerges when using trust learning models with a given detecting accuracy and how cooperation can still be sustained while reducing the cost and accuracy of those models. As another contribution, I also design and implement a general prototyping and simulation framework for reputation-based trust systems. The developed simulator can be used for many purposes, such as to discover new trust-related phenomena or to evaluate performance of a trust learning algorithm in complex settings. Two potential applications of computational trust models are then discussed: (1) the selection and ranking of (Web) services based on quality ratings from reputable users, and (2) the use of a trust model to choose reliable delegates in a key recovery scenario in a distributed online social network. Finally, I will identify a number of various issues in building next-generation, open reputation-based trust management systems as well as propose several future research directions starting from the work in this thesis.

EPFL2010

Peer-to-Peer Applications Beyond File Sharing: Overlay Network Requirements and Solutions

In this paper we analyze the functional and non-functional requirements of peer-to-peer (P2P) systems that go beyond the needs of the well explored file-sharing P2P systems. Four basic subcategories are suggested to classify the non-functional requirements: adaptability, efficiency, validity and trust. Similarly, the functional requirements are divided into user-triggered and system-triggered functions. Then, we present and discuss several existing solutions following different design approaches in order to reveal their suitability for different types of P2P applications. More particularly, we capture the characteristics of structured and unstructured overlay networks. For the structured solutions, we investigate distributed hash tables and lexicographic graph based solutions. For the unstructured approaches, we discuss both hierarchical and non-hierarchical overlay networks and emphasize on small-world and power-law networks. Finally, we provide a set of demanding application classes such as voice over IP and massive multiplayer online games that may be benefited by utilizing the P2P technology.

2006

Sampling Cluster Endurance for Peer-to-Peer based Content Distribution Networks

Several types of Content Distribution Networks are being deployed over the Internet today, based on different architectures to meet their requirements (e.g., scalability, efficiency and resiliency). Peer-to-peer (P2P) based Content Distribution Networks are promising approaches that have several advantages. Structured P2P networks, for instance, take a proactive approach and provide efficient routing mechanisms. Nevertheless, their maintenance can increase considerably in highly dynamic P2P environments. In order to address this issue, a two-tier architecture called Omicron that combines a structured overlay network with a clustering mechanism is suggested in a hybrid scheme. In this paper, we examine several sampling algorithms utilized in the aforementioned hybrid network that collect local information in order to apply a selective join procedure. Additionally, we apply the sampling algorithms on Chord in order to evaluate sampling as a general information gathering mechanism. The algorithms are based mostly on random walks inside the overlay networks. The aim of the selective join procedure is to provide a well balanced and stable overlay infrastructure that can easily overcome the unreliable behavior of the autonomous peers that constitute the network. The sampling algorithms are evaluated using simulation experiments as well as probabilistic analysis where several properties related to the graph structure are revealed.

2007

High Quality P2P Service Provisioning via Decentralized Trust Management

Hung Le Vu

EPFL2010