Where's Waldo? How to Mathematically Prove You Found Him without Revealing Where He Is

Abstraction: Zero-knowledge proofs explained via puzzles and cryptographic applications

Key points:

• Zero-knowledge proofs (ZKPs), formalized in a seminal 1989 SIAM paper, allow proving a claim without revealing any information beyond the claim's truth
• They are interactive (challenger queries prover repeatedly) and probabilistic (confidence grows with each successful round)
• Every claim provable by a traditional proof can also be proved in zero knowledge (proven in 1991 ACM paper)
• Practical applications include safer passwords, digital signatures, more secure cryptocurrency (e.g., Ethereum ZK-proofs), and secure electronic voting deployed in real elections
• A remarkable application: nuclear inspectors can verify warhead authenticity without learning any design secrets (published in Nature)
• Core insight: "Certainty does not require understanding"

Connections: Zero Knowledge Proofs · Cryptography · Interactive Proofs

Source: https://www.scientificamerican.com/article/wheres-waldo-how-to-prove-you-found-him-without-revealing-where-he-is/