Definition
Proof of work (PoW) requires a participant to demonstrate that computational work has been performed. In Bitcoin-style mining, this means finding a block-header hash below a protocol-defined target. A successful result is expensive to discover through repeated attempts but comparatively easy for other nodes to verify.
Role in Consensus
Miners compete to propose valid blocks. Nodes check those blocks and apply chain-selection rules based on cumulative work. The difficulty target adjusts according to the specific network’s rules. Creating extra identities does not by itself increase an attacker’s mining influence, because the limiting resource is effective computational work rather than an account count.
Key Considerations
PoW makes rewriting accepted history costly, but its security depends on the distribution and economics of available hash power. Confirmations reduce certain reversal risks without creating an absolute guarantee. Energy consumption, specialized hardware and mining concentration are relevant trade-offs. PoW does not let miners authorize spending without valid signatures or override other transaction rules. Not all blockchains use PoW; Ethereum’s mainnet moved to proof of stake in 2022.