Foundations of Blockchain

51% attack

If a participant in the network is able to control more than 50% of the resources required to reach the consensus to create blocks, then the block creation mechanism can be manipulated by that participant. The 51% attack can be performed on any of the consensus algorithms, but it is generally used in Proof of Work-based blockchain networks.

In a PoW-based network, if a dishonest participant is able to control the majority, that is, more than 50% of the computing resources in the network, the block creation process can be manipulated by the dishonest node. The feasibility information relating to the 51% attack was also mentioned by Satoshi Nakamoto in the Bitcoin whitepaper.