Proof of work and proof of stake are two ways a blockchain agrees on who gets to add the next block and keeps everyone honest without a central authority. Proof of work makes block producers spend real-world energy solving a puzzle; proof of stake makes them lock up the network's own coin as a deposit they can lose. Both aim to make cheating expensive — they just use electricity versus capital to do it.
The problem both solve
A blockchain has no boss. Thousands of strangers must agree on one shared history and stop anyone from, say, spending the same coin twice. This is the consensus problem. The trick is to make producing valid blocks cost something and to reward honest behaviour, so that attacking the network costs far more than it could ever gain.
Proof of work
In proof of work, machines called miners race to find a number that, combined with the block's data, produces a hash below a target. Finding it takes enormous trial-and-error computation; checking it is instant. The first to succeed proposes the block and collects a reward.
- Security comes from energy. To rewrite history, an attacker would need to out-compute the entire honest network — a 51% attack — which means buying and powering more hardware than everyone else combined.
- Difficulty adjusts so blocks arrive at a steady pace regardless of how much mining power joins.
- Bitcoin is the flagship example, as were many early chains.
The trade-off is obvious: it consumes a great deal of electricity and favours those with cheap power and specialised machines.
Proof of stake
In proof of stake, there are no miners. Instead, validators lock up (stake) the network's coin as collateral. The protocol picks validators to propose and attest to blocks, roughly in proportion to how much they have staked.
- Security comes from capital at risk. A validator who tries to cheat can be slashed — part or all of their stake is destroyed. Attacking the chain means risking a fortune in the very asset you'd be undermining.
