Consensus Mechanism

A consensus mechanism is the set of rules a blockchain network uses to agree on which transactions are valid and in what order they happened, without any central authority. Thousands of independent computers must reach the same conclusion, so the mechanism defines who may propose the next block, how everyone else checks it, and what rewards or penalties apply. Proof of work and proof of stake are the two best-known consensus algorithms, though variants such as delegated proof of stake also exist. A well-designed mechanism makes rewriting history expensive, which is what gives a public blockchain its tamper resistance. The trade-offs usually involve energy use, decentralisation, transaction speed and how quickly a payment becomes practically irreversible.