A Zero-Knowledge Proof (ZKP) is a cryptographic method where one party (the prover) can prove to another (the verifier) that they know a specific piece of information (like a password or transaction detail) without revealing the information itself. The proof satisfies three properties: completeness (if true, verifier is convinced), soundness (if false, verifier is not convinced), and zero-knowledge (verifier learns nothing else).
The concept was introduced by Shafi Goldwasser, Silvio Micali, and Charles Rackoff in their 1985 paper 'The Knowledge Complexity of Interactive Proof Systems'. They later received the Turing Award for this work.
ZKP has moved from theory to practice with the rise of blockchain. It is critical for privacy-preserving networks (like Zcash, Monero) and is the core technology behind ZK-Rollups, which scale Ethereum by bundling transactions off-chain while proving their validity.