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Glossary

Every term used internally that is not in the index of a standard cryptography textbook. Each entry links to the file in zcash/librustzcash (or an upstream crate) where the term is defined.

A​

  • Action: the Orchard analogue of a Sapling Spend + Output pair. One Action encodes a single nullifier, a single new note commitment, and a value contribution. Defined in orchard::action::Action.
  • ak: Orchard authorising key. Pallas point. Derived from ask.
  • Anchor: the Merkle root of the note-commitment tree at the block height the transaction commits to. Verifies note membership.

B​

  • bsk / bvk: Sapling and Orchard binding signing / verifying keys. They tie the value commitments to the rest of the transaction.

C​

  • cv: value commitment of a Spend, Output, or Action. Hides the note value.
  • cmu: note-commitment u-coordinate (Sapling); the value inserted into the Merkle tree.
  • Coinbase: the first transaction in a block. Special validity rules. See ZIP 213.

D​

  • d: diversifier byte string (11 bytes). Used to derive a diversified payment address.
  • DCO: Developer Certificate of Origin. The sign-off some contributions require (git commit -s).

E​

  • epk: ephemeral public key (Sapling) / equivalent in Orchard. Used in note encryption.
  • Equihash: the proof-of-work scheme used by Zcash. Defined in components/equihash.

F​

  • F4Jumble: invertible mixing function applied to Unified Addresses. Implemented in components/f4jumble. See ZIP 316.
  • FVK: Full Viewing Key. Decrypts incoming notes and observes outgoing transactions without spend authority.

G​

  • Groth16: the zk-SNARK system used by Sapling. Defined in bellman crate.

H​

  • hSig: Sprout transaction-level random value tying JoinSplits together.

I​

  • IPA: Inner Product Argument. The polynomial commitment scheme underneath Halo 2.
  • IVK: Incoming Viewing Key. Derived from FVK; can decrypt received notes only.

J​

  • JoinSplit: legacy Sprout transfer primitive.
  • Jubjub: Edwards curve over the BLS12-381 scalar field. Sapling in-circuit curve.

L​

  • LL: "Low-level". zcash_client_backend::data_api::ll is the low-level data API.

M​

  • Memo: 512-byte field accompanying a shielded note, encrypted to the recipient.

N​

  • nf: nullifier. Spent-note marker, public.
  • nsk: nullifier-deriving secret key.
  • Note: a shielded UTXO. Carries value, diversified address, randomness.

O​

  • OVK: Outgoing Viewing Key. Lets the sender decrypt their own outgoing notes after the fact.
  • out_ciphertext: the OutCiphertext field of a shielded output, encrypted under ovk.

P​

  • Pallas: Pasta-curve cycle partner of Vesta. Orchard in-circuit curve. Defined in pasta_curves/src/pallas.rs.
  • PCZT: Partially Created Zcash Transaction. Lives in pczt/.
  • PoW: Proof of Work. Equihash for Zcash.
  • prf_expand: domain-separated key-expansion PRF used widely across the protocol.

R​

  • RedDSA / RedJubjub / RedPallas: re-randomisable signature scheme used for spend authorisations and binding signatures.
  • rcm: note commitment randomness.

S​

  • Sapling: the second shielded pool. Jubjub + BLS12-381 + Groth16.
  • Sinsemilla: Pedersen-hash variant used inside Halo 2. Cheap with lookup tables.
  • Sprout: the first shielded pool. JoinSplit-based, BCTV14-then -Groth16. Deprecated for new transactions.
  • ssk: spend authorising secret key.

T​

  • t-address: transparent address (P2PKH or P2SH).
  • Test vector: stored expected outputs that cross-implementation tests are checked against. Lives next to the code or in test-data/.

U​

  • UA: Unified Address. Encoding combining multiple receiver types (transparent, Sapling, Orchard).
  • UFVK / UIVK: Unified Full / Incoming Viewing Key.

V​

  • Vesta: Pasta-curve cycle partner of Pallas. Defined in pasta_curves/src/vesta.rs.
  • vsk / vvk: value-balance signing / verifying keys (alternative names for bsk / bvk in some contexts).

Z​

  • z-address: shielded address (Sapling or Orchard).
  • ZIP: Zcash Improvement Proposal. Indexed at https://zips.z.cash/.