What is a 51% Attack? Double-Spending, Reorgs, and Immutability Limitations
Demystifying majority hashrate attacks: how dishonest miners reorganize chain history, what they CAN do, and what they CANNOT do.
Clear explanation of majority attacks: why attackers cannot steal private keys or create coins out of thin air, but can reverse their own prior transactions.
1. What an Attacker CAN and CANNOT Do
If a malicious entity controls >50% of network mining hashrate, they can secretly build a longer chain of blocks and broadcast it to cause a chain reorganization.
CRITICAL DISTINCTION: An attacker CANNOT forge cryptographic signatures, steal coins from arbitrary addresses, or alter protocol consensus rules (such as the 21M limit), because non-mining full nodes automatically reject invalid transactions.
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