A 51% attack is when a single entity or group of miners controls more than 50% of the hashing power on a blockchain network. This allows them to manipulate transactions, double-spend coins, and potentially disrupt the network's consensus mechanism.
Blockchains can defend against 51% attacks by implementing the following measures:
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Proof of Work Consensus: Increasing the computational power required to control the network makes it more difficult and expensive for an attacker to amass 51% of the hashing power.
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Proof of Stake Consensus: This consensus mechanism requires validators to lock up a certain amount of cryptocurrency, reducing the likelihood of a successful attack as it would require owning a majority of the cryptocurrency.
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Network Monitoring: Constantly monitoring the network for suspicious activity can help detect and mitigate potential 51% attacks.
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Decentralization: Ensuring that no single entity or group controls a significant portion of the network's hashing power can help prevent 51% attacks.
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Hard Forks and Network Upgrades: Implementing changes to the blockchain's protocol through hard forks or network upgrades can help strengthen the network's security against potential attacks.
