An attacker with 51% of the hash power on a proof-of-work blockchain can do the following:
They can execute double-spend attacks by creating a forked chain with conflicting transactions and overriding the original chain. This would allow them to spend the same coins twice on different exchanges or merchants, defrauding them of their funds.[1][2][3]
The attacker can also censor transactions by excluding them from the blocks they create or rejecting blocks that contain them, preventing users from sending or receiving payments, accessing decentralized applications, or participating in smart contracts.[1][3]
Furthermore, the attacker can disrupt the normal functioning of the consensus protocol, creating uncertainty and confusion among users and nodes. This can lead to a decrease in confidence in the blockchain's validity and value, causing market volati...
