Zero-Knowledge
Zero-Knowledge Proof (ZK)
A cryptographic technique that proves a statement is true without revealing the data behind it.
A zero-knowledge proof lets one party (the prover) convince another (the verifier) that they know some piece of information, without disclosing the information itself. The canonical example: prove that you are over 18 without revealing your date of birth.
In production, ZK shows up in two flavors. ZK-SNARKs are smaller and faster to verify but require a trusted setup. ZK-STARKs are larger and slower but need no trusted setup and are post-quantum safe. Most chains now offer pre-built circuits for common proofs (identity, balance, voting eligibility) so you do not need a cryptographer on staff.
The business case is narrower than the hype: ZK is genuinely valuable when you need to prove a property on-chain (or to a counterparty) without leaking the data. It is overkill for most consumer apps.