A consensus mechanism is a protocol that allows distributed nodes in a blockchain network to agree on the current state of the ledger. It ensures all participants have the same copy of the blockchain.
Common consensus mechanisms include: Proof of Work (PoW) used by Bitcoin, requiring computational power to validate transactions. Proof of Stake (PoS) used by Ethereum, where validators stake tokens. Delegated Proof of Stake (DPoS) where token holders vote for validators. Proof of Authority (PoA) for permissioned networks.
The choice of consensus mechanism affects network security, decentralization, scalability, energy consumption, and transaction speed.
Newer mechanisms like Proof of History (Solana) and Proof of Space (Chia) aim to address limitations of earlier protocols.