01Definition
Bitcoin miners repeatedly hash candidate block headers until one falls below the network target. The winning proof is expensive and uncertain to find but trivial for nodes to verify.
02What the work proves
Proof of work does not prove that a block is valid; nodes still verify every rule and transaction. It proves that computational energy was committed to a particular candidate history.
03Security model
Rewriting a confirmed payment requires rebuilding its block and overtaking the honest chain’s continuing work. The cost rises with additional confirmations, while users choose how much confirmation is appropriate for the value and risk.
⌖Reference points
01
Uses SHA-256 hashing
02
Hard to produce, cheap to verify
03
Does not replace node validation
04
Makes history costly to rewrite