What Is the ‘Longest Chain Rule’ in Blockchain Consensus?
The longest chain rule, also known as the Nakamoto consensus, is a fundamental principle in Proof-of-Work blockchains. It dictates that nodes should always consider the chain with the most cumulative Proof-of-Work (i.e. the most blocks or the highest total difficulty) as the valid, canonical chain.
An attacker in a 51% attack attempts to secretly build a longer, malicious chain to replace the honest one.
Glossar
Longest Chain Rule
Consensus Rule ⎊ Longest Chain Rule is the fundamental protocol mechanism dictating that in the event of a temporary fork, the chain exhibiting the greatest cumulative proof of work or stake is recognized as the canonical and valid history, thus finalizing transactions.
Longest Chain
Consensus ⎊ The longest chain rule is the core mechanism for achieving consensus in Proof-of-Work systems like Bitcoin.
Chain Split
Protocol Division ⎊ A Chain Split represents a fundamental divergence in the transaction history of a blockchain, resulting in two separate, independently operating ledgers that share a common past up to the point of the split.