What is a zero-knowledge proof? Privacy and scaling explained

A zero-knowledge proof lets one party prove to another that a statement is true without revealing any information beyond the truth of the statement itself. It is the cryptographic technique behind blockchain privacy, scalable rollups, and a growing number of identity verification systems. Summary Zero-knowledge proofs allow a prover to convince a verifier that a computation was performed correctly without revealing the underlying data, enabling both privacy and scalability on blockchains. The two main families of zero-knowledge proofs used in blockchain are zk-SNARKs, which require an initial trusted setup ceremony, and zk-STARKs, which do not require trusted setup but produce larger proofs. Ethereum layer 2 rollups like zkSync, Scroll, and Polygon zkEVM use zero-knowledge proofs to compress thousands of transactions into a single proof verified on the main chain, reducing gas costs by 90 percent or more. Vitalik Buterin introduced the GKR protocol in late 2025 as a way to accelerate Ethereum zero-knowledge proof verification, aiming to make the technology practical for everyday use at scale. Zero-knowledge proofs are mathematically sound but not magic. They depend on specific cryp...