# A Survey on Consensus Protocols and Attacks on Blockchain Technology
## 1 Introduction

Table 3: _Cont._The paper is arranged as follows. Section 2 describes blockchain, how it works, and its structure. Section 3 describes the types of blockchains. Section 4 describes the literature on consensus protocols. Section 5 includes the classification of attacks on blockchain. Section 6 discusses the DDoS attacks and ARP spoofing attacks. Section 7 describes other recent important attacks. Section 8 includes some of the preventive measures from past works and research. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Authors** & **Attack** & **Targeted Area** & **Effect of Attack** \\ \hline [PERSON] et al. 2013 [55] & Brute Force & Computing Power & Data Encryption \\ \hline [PERSON] et al. 2017 [56] & Refund & Payment Protocol & Lose Reputation \\ \hline [PERSON] et al. [57] & Wallet & Private key & Loss of Bitcoin \\ \hline [PERSON] et al. 2014 [58] & Time Hijacking & Network & Fake Peers \\ \hline [PERSON] et al., 2016 [59] & Long Range & Database & Changes the Transaction History \\ \hline [PERSON] et al. 2010 [60] & BGP Hijacking & Database Protocol & Fake Transaction \\ \hline [PERSON] et al. 2017 [61] & Sybil & Network & Pseudonymous Identities \\ \hline  & DDoS & Network & Unnecessary messages about transaction \\ \hline [PERSON] et al. 2018 [50] & Eclipse Attack & Network & Different view of the network \\ [PERSON] 2018 [62] & & & \\ \hline [PERSON] 2018 [63] & DAO & Computing Power & Fake Transaction \\ \hline Hackernoon 2018 [64] & Nothing at Stack & Block & Slow Consensus \\ \hline [PERSON] et al. 2020 [65] & Pool Mining & Block & Slow Verification Time \\ \hline [PERSON], [PERSON] et al. 2018 [66] & Double Spending & Bitcoin Transactions, Pow & Lose Products \\ \hline [PERSON] and [PERSON] 2018 [67] & Selfish Mining & Computing Power & Enhance Personal Share on Transaction \\ \hline [PERSON] 2018 [68] & Spam & Network & Slow Transaction Network \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Attacks and their targeted areas and effect. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Authors** & **Consensus Protocols** & **Outcome** \\ \hline  & Stellar consensus protocol (SCP), & They focused on analyzing the feasibility and efficiency of these \\ [PERSON] et al. [29], 2017 & Byzantine fault tolerance (BFT) & consensus protocols. \\ \cline{2-3}  & Survey of consensus protocols on & They had surveyed previously proposed consensus protocols \\  & blockchain applications & and analyzed their efficiency characteristics. \\ \hline  & & Surveyed consensus protocols for IoT networks where they \\ [PERSON]. et al. [69], 2018 & PoW, PoS, PoC, PoET, DPoS & reviewed existing consensus methods that have been \\  & & implemented to realize a blockchain-based IoT network and \\  & & also discussed open research challenges in blockchain and \\  & & IoT networks. \\ \hline  & & Surveyed some popular consensus protocols and identified that \\ [PERSON] et al. [70], 2018 & PoW, PoS, PoL & each protocol has its own strengths and weaknesses. They \\  & & conclude that many researchers are working to develop a \\  & & scalable, secure, and efficient consensus protocol for the growth \\ \hline [PERSON], [PERSON] et al. [71], 2020 & Classical fault tolerance consensus and & They conducted this survey on the basis of fault tolerance, \\  & general blockchain consensus protocols & performance, and vulnerabilities. \\ \hline  & & \\ [PERSON] et al. [72], 2022 & Consensus algorithms which are based on & Analyzed all six variants of PoW on the basis of the scalability \\  & PoW (proof of work) & maintenance cost, pros, cons, and block generation time, \\  & transaction cost, energy consumptions, etc. \\ \hline [PERSON], et al. [73],2021 & General consensus protocols & Conducted a comprehensive survey of consensus algorithms \\  & & on the basis of their transaction, performance, and architecture. \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Previous surveys and their outcome.