Definition
A consensus mechanism coordinates participants that may receive information at different times or act dishonestly. In a blockchain, it helps determine which valid blocks form the accepted history. Agreement and validity are connected but distinct: a block must satisfy transaction rules as well as the network’s process for selecting history.
How It Works
Proof of work uses computational effort to limit influence over block production, while proof of stake uses committed assets and protocol-defined validator duties. These labels describe important components, but a complete design also includes rules for choosing between competing histories, handling votes or confirmations and establishing finality. Different mechanisms make different assumptions about participants and network conditions.
Key Considerations
Consensus lets participants coordinate without assuming that every operator is trustworthy. It does not prove that information entered into a ledger reflects events outside the network. Security depends on the stated assumptions, incentive design, implementation and distribution of control. A high transaction rate or a large validator count alone does not establish strong consensus security, and temporary agreement should not always be confused with final settlement.