Zero-knowledge Proof
A proof that reveals no more information than the validity of the statement it supports.
A proof is said to be “zero-knowledge” if it does not reveal any information beyond the fact that a statement is TRUE
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Zero-knowledge proofs provide privacy for the prover. Any other proof system is bound to leak at least 1 bit of information, which could have very subtle privacy and security implications.
See S2M1 of the ZK Whiteboard Sessions for an in-depth treatment of how we define zero-knowledge mathematically and prove it.
Warning: implementation bugs. Zero-knowledge is only shown to hold for honest provers. A malicious or faulty prover (e.g., the implementation has bugs) may produce proofs that leak information about the private input.