How to Pick Your Friends - A Game Theoretic Approach to P2P Overlay Construction

TL;DR

This paper introduces a game theoretic framework for constructing resilient P2P overlay networks, specifically addressing Sybil attacks by strategic peer selection, with practical application to Bitcoin's network.

Contribution

It develops a novel game theoretic model for P2P overlay construction that enhances attack resistance and applies it to Bitcoin, demonstrating improved security strategies.

Findings

Cost of attacks increases with strategic peer selection.

Effective strategies can guarantee high safety levels against Sybil attacks.

Application to Bitcoin shows practical security improvements.

Abstract

A major limitation of open P2P networks is the lack of strong identities. This allows any agent to attack the system by creating multiple false personas, thereby disrupting the overlay network's connectivity and sabotaging its operation. In this paper, we explore practical ways to defend P2P networks from such attacks. To do so, we employ a game theoretic approach to the management of each peer's list of known nodes and to the overlay construction mechanisms that utilize this list. We consider the interaction between defender and attacker agents as a zero-sum game. We show that the cost of attacks can be driven up substantially if the defender utilizes available information about peers it chooses to connect to, such as their IP address. In addition to theoretical analysis of the underlying game, we apply our approach to the Bitcoin P2P network and derive effective strategies that guarantee a high safety level against attacks.