A zero-knowledge proof is a cryptographic primitive that lets a prover convince a verifier that a statement is true, without revealing any information beyond that fact.
In Web3, ZK proofs power:
- ZK rollups, where the prover demonstrates that an off-chain batch of transactions was executed correctly.
- Privacy protocols, where a user proves they own assets, are eligible for an action, or have paid a fee, without revealing identity or balance.
- ZK identity, where claims about a user (over 18, holds a passport, has a credit score above X) can be proven without exposing the underlying credential.
The dominant proof systems are SNARKs (Groth16, PLONK, Halo2) and STARKs. They differ in proof size, prover cost, and trust assumptions (SNARKs typically require a trusted setup; STARKs do not).
ZK is one of the most active areas of cryptography research, and one of the highest-stakes audit surfaces in Web3, a soundness bug in a proof system can let an attacker generate proofs for false statements.