51% Attack

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A condition in which more than half the computing power on a cryptocurrency network is controlled by a single miner or group of miners. That amount of power theoretically makes them the authority on the network. This means that every client on the network believes the attacker's hashed transaction block. This gives them control over the network, including the power to:

• Issue a transaction that conflicts with someone else's.
• Stop someone else's transaction from being confirmed.
• Spend the same coins multiple times.
• Prevent other miners from mining valid blocks.