Improving Bitcoin Transaction Propagation by Leveraging Unreachable Nodes

TL;DR

This paper explores the role of unreachable nodes in Bitcoin's network, proposing protocol modifications to enhance transaction propagation, robustness, and privacy against deanonymization attacks.

Contribution

It introduces a novel protocol involving unreachable nodes to improve propagation efficiency and privacy, addressing a gap in existing Bitcoin network analyses.

Findings

Unreachable nodes can significantly improve message propagation.

Protocol modifications involving unreachable nodes enhance network robustness.

The proposed solutions are simple and provide immediate benefits.

Abstract

The Bitcoin P2P network is at the core of all communications between clients. The reachable part of this network has been explored and analyzed by numerous studies. Unreachable nodes, however, are, in most part, overlooked. Nonetheless, they are a relevant part of the network and play an essential role in the propagation of messages. In this paper, we focus on transaction propagation and show that increasing the participation of unreachable nodes can potentially improve the robustness and efficiency of the network. In order to do that, we propose a few changes to the network protocol. Additionally, we design a novel transaction propagation protocol that explicitly involves unreachable nodes to provide better protection against deanonymization attacks. Our solutions are simple to implement and can effectively bring immediate benefits to the Bitcoin network.