ProofofWork

Proof of work is a consensus mechanism used by some blockchain networks to achieve agreement on a single ledger without a central authority. In PoW, miners compete to solve computational puzzles. The puzzle requires finding a nonce so that the hash of the block header and nonce is below a target. The first solver broadcasts the new block; other nodes verify and add it to their chains. The process is deliberately resource-intensive to deter manipulation.

Block creation consumes energy and time. Difficulty adjusts to keep block times near a target; for Bitcoin, the goal is about ten minutes per block, with retargeting every roughly 2016 blocks. A miner’s chance of solving the puzzle is proportional to its hash power, so larger operations have a higher probability of earning rewards in the form of newly minted coins and collected transaction fees.

Security rests on the honest majority of hash power. Damaging the chain would require re-mining blocks after the point of attack, which becomes costly as the chain grows. PoW has demonstrated robustness and censorship resistance, but it faces concerns about energy use and potential centralization of mining power.

Alternatives include proof of stake and hybrid models. Some networks combine PoW with other methods to balance security, efficiency, and governance. The choice of consensus mechanism influences security assumptions, performance, and environmental impact.