Mario T. Schlosser

The Eigentrust algorithm for reputation management in P2P networks

Peer-to-peer file-sharing networks are currently receiving much attention as a means of sharing and distributing information. However, as recent experience shows, the anonymous, open nature of these networks offers an almost ideal environment for the spread of self-replicating inauthentic files.We describe an algorithm to decrease the number of downloads of inauthentic files in a peer-to-peer file-sharing network that assigns each peer a unique global trust value, based on the peers history of uploads. We present a distributed and secure method to compute global trust values, based on Power iteration. By having peers use these global trust values to choose the peers from whom they download, the network effectively identifies malicious peers and isolates them from the network.In simulations, this reputation system, called EigenTrust, has been shown to significantly decrease the number of inauthentic files on the network, even under a variety of conditions where malicious peers cooperate in an attempt to deliberately subvert the system.

A scalable and ontology-based P2P infrastructure for Semantic Web Services

Semantic Web Services are a promising combination of Semantic Web and Web service technology, aiming at providing means of automatically executing, discovering and composing semantically marked-up Web services. We envision peer-to-peer networks which allow for carrying out searches in real-time on permanently reconfiguring networks to be an ideal infrastructure for deploying a network of Semantic Web Service providers. However, P2P networks evolving in an unorganized manner suffer from serious scalability problems, limiting the number of nodes in the network, creating network overload and pushing search times to unacceptable limits. We address these problems by imposing a deterministic shape on P2P networks: We propose a graph topology which allows for very efficient broadcast and search, and we provide an efficient topology construction and maintenance algorithm which, crucial to symmetric peer-to-peer networks, does neither require a central server nor super nodes in the network. We show how our scheme can be made even more efficient by using a globally known ontology to determine the organization of peers in the graph topology, allowing for efficient concept-based search.

HyperCuP: hypercubes, ontologies, and efficient search on peer-to-peer networks

Peer-to-peer networks are envisioned to be deployed for a wide range of applications. However, P2P networks evolving in an unorganized manner suffer from serious scalability problems, limiting the number of nodes in the network, creating network overload and pushing search times to unacceptable limits. We address these problems by imposing a deterministic shape on P2P networks: We propose a graph topology which allows for very efficient broadcast and search, and we describe a broadcast algorithm that exploits the topology to reach all nodes in the network with the minimum number of messages possible. We provide an efficient topology construction and maintenance algorithm which, crucial to symmetric peer-to-peer networks, does neither require a central server nor super nodes in the network. Nodes can join and leave the self-organizing network at any time, and the network is resilient against failure. Moreover, we show how our scheme can be made even more efficient by using a global ontology to determine the organization of peers in the graph topology, allowing for efficient concept-based search.

Incentives for Combatting Freeriding on P2P Networks

We address the freerider problem on P2P networks. We first propose a specific participation metric, which we call a peer’s EigenTrust score. We show that EigenTrust scores accurately capture several different participation criteria. We then propose an incentive scheme that may be used in conjunction with any numerical participation metric. We show that, when these incentives are used in conjunction with EigenTrust scores, they reward participatory peers but don’t exclude less active peers.

Peer-to-peer research at Stanford

n this paper we present recent and ongoing research projects of the Peers research group at Stanford University.