DocsGlossary
Zero-knowledge glossary
The terms on these pages, in one place.
- Commitment
- A value that fixes some data without showing it, like a sealed envelope: it can't be changed later, and it can be opened to prove what was inside.
- Completeness
- A proof's promise that an honest prover with a true statement always convinces the verifier. See precisely.
- DLEQ proof
- A proof of discrete-logarithm equality: two pairs of points share one secret multiplier, without revealing it. In RFC 9497 it shows that a server used the key it published. See invite tokens.
- Fiat-Shamir transform
- Replaces the verifier's random challenge with a hash, turning an interactive proof into one message anyone can check (Fiat and Shamir, 1986).
- Interactive proof
- A proof made of messages back and forth, whose force comes from the verifier's random challenges (Goldwasser, Micali and Rackoff, 1985).
- Key transparency
- A public, append-only log of which key belongs to which account, so a swapped key can be noticed. See Midnight.
- Message franking
- A commitment each message carries to its own content, so a reported message can be shown to be genuine. Asymmetric message franking adds a signature of knowledge that only the recipient and the moderator can check.
- Midnight
- A blockchain whose contracts run as zero-knowledge circuits, a partner chain to Cardano. See Midnight.
- Oblivious PRF (OPRF)
- A protocol in which a client gets a server's keyed pseudorandom function of its input, while the server doesn't see the input and the client doesn't learn the key (RFC 9497). It is not a proof.
- Proof of knowledge
- A proof that the prover knows a witness, not only that one exists: an extractor could pull the witness out of any prover that convinces.
- Prover and verifier
- The side that proves a statement, and the side that checks it. In Schnorr's protocol the prover sends a commitment and a response, and the verifier picks the challenge (live).
- Sigma protocol
- A three-move proof: commit, challenge, respond. Schnorr's protocol (1989) is the classic one.
- Signature of knowledge
- A non-interactive zero-knowledge proof of knowledge bound to a message, so it signs that message.
- Simulator
- An algorithm that, without the witness, produces transcripts that look like real ones. If one exists, the proof is zero knowledge.
- Soundness
- A proof's promise that a false statement convinces the verifier only with negligible probability.
- Statement and witness
- What is proved (public), and the secret that makes it true (kept by the prover).
- Verifiable OPRF (VOPRF)
- An OPRF whose server also sends a DLEQ proof that it used its committed key. Pigeon's invite tokens use one (RFC 9497, mode 0x01).
- Zero-knowledge proof
- A proof that a statement is true which reveals nothing else. See what it is.
- zk-SNARK
- A zero-knowledge succinct non-interactive argument of knowledge: a short proof, quick to check, of a statement written as a circuit.