Proof of Stake is a blockchain consensus mechanism where validators are chosen to propose and attest to blocks based on how much cryptocurrency they have staked as collateral, rather than through computational work. Validators lock up tokens as security deposits. If they act honestly, they earn rewards. If they attempt to cheat by double signing or proposing invalid blocks, their stake is slashed. Security comes from economic alignment rather than energy expenditure. Ethereum transitioned to Proof of Stake in 2022's Merge event, reducing its energy consumption by approximately 99.95%. Validators must stake 32 ETH to participate directly, though liquid staking protocols allow smaller holders to participate collectively. The criticism of Proof of Stake is that it may favor wealth concentration: larger stakers earn more rewards and compound their relative position. Critics also question whether economic security equals the physical security of Proof of Work's energy expenditure. Proponents counter that the slash conditions are severe, the validator set is diverse, and the economics are sound. Most new blockchain networks use Proof of Stake variants, and even Bitcoin's ecosystem has seen Lightning Network development to complement its Proof of Work base.
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