Glossary

Bitcoin terms

Bitcoin output / UTXO

A specific amount of bitcoin created by a transaction and not yet spent. QuietProof requests identify outputs by transaction ID and output index.

Compressed public key

A 33-byte secp256k1 key revealed when spending P2WPKH outputs. QuietProof does not disclose it, but cannot hide disclosures elsewhere, including spends with the same key.

Private key / spend key

The secret scalar that authorizes spending. QuietProof’s prover uses it locally as a private witness. It must never be placed in command arguments, shell history, environment variables, requests, or proof files.

P2WPKH

“Pay to Witness Public Key Hash,” a common native SegWit output type. Its witness program contains a 20-byte HASH160 fingerprint of the compressed public key.

Witness program

For P2WPKH, the 20 bytes after 0014 in the output’s scriptPubKey. This public fingerprint is an input to the QuietProof relation.

Proof terms

Challenge

A short-lived request created by the verifier. It identifies the verifier, purpose, network, outputs, nonce, and expiry.

Circuit

The arithmetic rules checked by the zero-knowledge proof. QuietProof v1 has exact circuit shapes for one and two distinct witness programs.

Nonce

A fresh random value used once. Together with durable consumption, it prevents the same proof conversation from being replayed as a new one.

PoKC

Proof of Key Control, the underlying zero-knowledge relation used by QuietProof.

Prover

The party that supplies the private key locally and creates the proof.

Statement

The canonical public data bound into the proof: version, network, verifier, purpose, message, times, nonce, claims, and optional bindings.

Verifier

The party or software that checks the proof, expected policy, replay state, and independent Bitcoin evidence.

Witness

Private data used to satisfy a zero-knowledge circuit. Here it includes the spend key and derived intermediate values. “Witness” in the proof-system sense is separate from Bitcoin transaction witness data.

Zero-knowledge proof

Evidence that a private relation is true without revealing the private values that make it true.