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What is a zero-knowledge proof?
A zero-knowledge proof is a way for one party to prove a statement is true to another without revealing anything beyond the fact that it is true. For example, someone could prove they are over a certain age without showing their date of birth.
What it means for you
Zero-knowledge proofs are what let ZK-rollups prove a batch of transactions is correct, and what some privacy coins use to hide transaction details. Some proof systems depend on a one-time setup ceremony; if it was mishandled, false proofs could be possible, so a project's published account of its setup is worth reading.
A common mistake: “Anything using zero-knowledge proofs is private.”
In fact: A ZK-rollup uses proofs to show a batch is correct, but it still posts a summary of the state changes to Ethereum, where anyone can read it. A proof hides only what its designers chose to hide.
How it works
A prover holds secret information, the witness, and convinces a verifier through challenges and responses. A valid protocol needs three properties: completeness (an honest prover with a true statement succeeds), soundness (a false statement fails except with negligible probability) and zero-knowledge (the verifier learns nothing beyond true or false). Blockchains mostly use non-interactive forms: SNARKs, which are small and fast but need a setup ceremony, and STARKs, which need no setup and are described as quantum-resistant but produce larger proofs.
Sources: ethereum.org: Zero-knowledge proofs, ethereum.org: Zero-knowledge rollups · checked 4 October 2026
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