# A Survey on Consensus Protocols and Attacks on Blockchain Technology
## 1 Introduction
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Authors** & **Attack** & **Description** \\
**Year** & & This sort of assault targets the architecture, components, and protocols of the blockchain. It spreads to the lower levels, including the machines that run them and the industry network protocols that those machines use to connect with one another. \\ \hline Transaction malleability & The signature secures the transaction, but nothing secures the signature. The purpose of a hacker could be to sabotage the transaction by modifying the signature in an arbitrary way, rendering it invalid. As a result, the transaction is canceled. \\ \hline Liveness attack & These attacks operate in three stages: delay, prep, and deny, and can cause a delay in the target transaction’s acknowledgment. During the preparation process, the attacker seeks to gain an advantage over honest players in order to establish an isolated blockchain. If the attacker thinks the delay is not long enough, they move on to the blockchain render step, where they try to slow down the chain transaction’s growth rate. \\ \hline Spatial partitioning and BGP hijacking & The full nodes’ ledger views and the simplified payment verification nodes’ ledger views are derived from the nodes. The entire nodes are widely dispersed over the globe. By owning one or more independent systems that perform traffic routing, ISPs control the flow of traffic on the web. A hostile AS that hosts the majority of full nodes can intercept communication from a target AS. \\ \hline Stress testing & DDoS stress testing is a service that evaluates a company’s readiness for several DDoS attack scenarios and flood magnitudes. Controlled tests are performed on your IT infrastructure at a predetermined period and with real-time online assistance. \\ \hline [PERSON] et al. 2022, [47] & Memory pool flooding & This is a one-of-a-kind DDoS attack. Miners usually prioritise communications in the memory pool grounded on the mining payment. To put it another way, the highest-mining-fee transactions are chosen and mined first. \\ \hline Block withholding & Malicious nodes commit this act by purposefully masking, forging, or withholding critical information that must be relayed across the network. \\ \hline [PERSON] & In this attack, the miner can generate a block containing a transaction from address A to address B, where both addresses belong to them. Then, using the same currencies, you will make another payment from address A to address C. (which belongs to another user). If the user accepts the transaction without receiving network confirmation, the attacker can release the block containing their initial transaction. This renders the merchant’s transaction invalid, allowing the attacker to double spend. \\ \hline \multirow{2}{*}{51\% attack} & This is a situation in which a single entity or organisation controls 50\% or more of the hashing rate computation power. In such a case, the mining will always be won by the attacker. \\ \hline Consensus delay & This form of attack aims to inject latency into the network, resulting in block rejection, and preventing peers from achieving consensus on any other sabotage reasons or status of the blockchain, and this could be accomplished in a number of ways. They could inject erroneous blocks, such as blocks with double-spending transactions. \\ \hline Client-oriented attack & This section looks into attacks on blockchain client programs, such as those that run on user or miner machines. \\ \hline Wallet thief & If malware is installed on a computer, it may be possible to steal a user’s private keys or conduct transactions as their representative unless those keys are protected and encrypted. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Attacks on the blockchain with description.