What is a 51% attack?

@millie 

A 51% attack, also known as a majority attack or double-spending attack, is a potential security threat in blockchain-based cryptocurrencies. In this attack, a single entity or group of miners gains control over more than 50% of the network's mining hash power. With majority control, they can manipulate the blockchain transactions.

Once the attacker controls the majority, they can engage in various malicious activities. One common goal is to reverse transactions and perform double-spending, where they spend the same coins multiple times. By controlling more than half of the network, the attacker can create a longer private branch of the blockchain and eventually replace the public blockchain's legitimate transactions.

Furthermore, a 51% attacker can prevent new transactions from being confirmed, excluding other miners' blocks from the blockchain. This ability creates centralization and undermines the decentralized nature of cryptocurrencies.

A successful 51% attack requires significant computational power and resources, making it more feasible for smaller cryptocurrencies with lower mining capabilities. Consequently, larger and more popular cryptocurrencies are generally considered resistant to these attacks due to their vast network of miners.