LAUSR

Over the last decade, Bitcoin has revolutionized the global economic and technological landscape, inspiring a new generation of blockchain-based technologies. Its protocol is today among the most influential for cryptocurrencies and distributed networks. In particular, the P2P layer represents a reference point for all permissionless blockchains, which often implement its solutions in their network layer. Unfortunately, the Bitcoin network protocol lacks a strong security model, leaving it exposed to several threats. Attacks at this level can affect the reliability and trustworthiness of the consensus layer, mining the credibility of the whole system. It is therefore of utmost importance to properly understand and address the security of the Bitcoin P2P protocol. In this paper, we give a comprehensive and detailed overview of known network-level attacks in Bitcoin, as well as the countermeasures that have been implemented in the protocol. We propose a generic network adversary model, and propose an objective-based taxonomy of the attacks. Finally, we identify the core weaknesses of the protocol and study the relationship between different types of attack. We believe our contribution can help both new and experienced researchers have a broader and deeper understanding of the Bitcoin P2P network and its threats, and allow for a better modeling of its security properties.