Surround voting, also known as a surround attack or eclipse attack, is a type of attack that targets vulnerabilities in peer-to-peer (P2P) blockchain consensus protocols. Surround voting primarily affects decentralized blockchain networks (or P2P blockchains), such as those using consensus mechanisms like [[Proof of Stake]] (PoS) or Delegated Proof of Stake (DPoS). These types of chains are more vulnerable because they depend on reputation-based systems, where stakeholder influence determines decision-making power within the network. Such influence can make a node a target. In a surround attack, malicious nodes attempt to isolate and control a target node by surrounding it. The goal is to manipulate the target node's view of the network and influence its decision-making process. While surround voting attacks may not be common in practice, they represent real risks that developers and researchers consider when designing and securing blockchain protocols. >[!example] Example >This vulnerability was described in [Eclipse Attacks on Bitcoin's Peer-to-Peer Network](https://www.usenix.org/system/files/conference/usenixsecurity15/sec15-paper-heilman.pdf), a 2015 research paper published by researchers Ethan Heilman, Alison Kendler, Aviv Zohar, and Sharon Goldberg. The paper outlined how attackers could manipulate incoming connections to isolate targeted nodes and control their view of the network. In response to this vulnerability - and other potential attacks on Bitcoin's P2P network layer - some improvements were made to Bitcoin's protocol: 1. [[Bitcoin Proposals#BIP 150 (Encryption and Authentication for Peer Communication)|BIP 150]]: This Bitcoin Improvement Proposal introduced encryption and authentication mechanisms for peer communication using Transport Layer Security (TLS). It aimed to enhance security against various attacks targeting P2P communications. 2. [[Bitcoin Proposals#BIP 151 (Message-Level Encryption)|BIP 151]]: This proposal added message-level encryption to protect data exchanged between peers within the Bitcoin network. It helped prevent eavesdropping or tampering with messages during transmission. 3. [[Bitcoin Proposals#BIP 152 (Compact Block Relay)|BIP 152]]: Also known as Compact Block Relay (CBR), this improvement focused on optimizing block propagation efficiency across the network by reducing bandwidth requirements and maintaining security. In the Ethereum protocol, there are mechanisms in place to penalize surround voting attempts. For example: * [[Slashing]]: Ethereum's consensus mechanism includes slashing conditions for validators who engage in malicious behavior such as surround voting. Validators can have their staked funds "slashed" if they are found guilty of participating in activities that harm the network's security or integrity. The consequences of a successful surround voting attack range from minor to severe: 1. [[Double-spending]]: By isolating a target node from honest nodes, attackers can potentially execute double spending attacks where they spend their cryptocurrency twice by manipulating the victim's view of transactions. 2. Denial-of-Service (DoS): Surrounding a target node with malicious nodes can lead to a denial-of-service, preventing legitimate transactions from being processed or slowing down the network significantly. 3. Network Partitioning: If an attacker successfully surrounds multiple important nodes simultaneously, they could create network partitions leading to one or more [[Forks|forks]] in the blockchain. 4. [[Inactivity Leak]]: By controlling enough surrounding nodes, attackers may be able to manipulate PoS or DPoS consensus, creating chaos or confusion, which could delay or stall consensus.