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Glossary

1. Why this chapter exists​

zcashd uses many terms and abbreviations whose meaning is not obvious from their letters. A reader who does not recognise "IVK" or "valueBalance" will silently misread code. This is a flat alphabetical list, with each entry pointing to the file where the term is defined or first used.

2. Definitions​

A​

  • addrman - The peer-address manager, CAddrMan. See src/addrman.h.
  • addrv2 - Address relay message v2 (BIP 155); supports Tor v3, I2P, CJDNS. Handled in src/net.cpp.
  • AEAD - Authenticated Encryption with Associated Data. The note ciphertexts use AEAD constructions.
  • ak - Sapling spend authorising public key. See src/zcash/address/zip32.h.
  • anchor - The root of a note commitment tree at the time of a spend. Stored per spend description.
  • API tx - A transaction received via sendrawtransaction or z_sendmany, vs one received over P2P.
  • ask - Sapling spend authorising secret key. See src/zcash/address/zip32.h.

B​

  • BatchValidator - The Rust object that accumulates Sapling or Orchard bundles and verifies them as a single batched call. See src/rust/src/sapling.rs and src/rust/src/orchard_ffi.rs.
  • BDB - BerkeleyDB. The wallet storage format. See src/wallet/db.h.
  • bindingSig - The single per-bundle binding signature that ties the value commitments to valueBalance.
  • BLAKE2b/BLAKE2s - The Zcash hash family. Personalised variants are pervasive.
  • BLS12-381 - The pairing-friendly curve used by Sapling. Outer curve.
  • BN-254 - The pairing-friendly curve used by Sprout.
  • branch ID - A 32-bit identifier for each network upgrade, enforced in transaction sighashes from Overwinter onward. Defined in src/consensus/upgrades.cpp.
  • bundlecache - Per-bundle validation cache. See src/rust/src/bundlecache.rs.

C​

D​

  • DA / FLTS - Terms from the spec's automata vocabulary; rarely surface in code.
  • d (diversifier) - 11-byte randomness in a Sapling/Orchard address.
  • dust - Outputs smaller than the per-pool dust threshold; see ZIP-205, ZIP-206.

E​

  • ECC - Electric Coin Company. Historical maintainer.
  • epk - Ephemeral public key in a Sapling/Orchard note encryption.
  • enc_ciphertext - The recipient-facing note ciphertext.
  • Equihash - The proof-of-work algorithm. See src/crypto/equihash.h.
  • esk - Ephemeral secret key (sender side of note encryption).

F​

  • F4Jumble - The four-round Feistel used in ZIP-316 Unified Address encoding.
  • fOverwintered - Consensus flag on a transaction asserting it is in Overwinter format.
  • FFI - Foreign-function interface. Two flavours in this repo: the original extern "C" (src/rust/include/rust/*.h) and the newer cxx-bridge (src/rust/src/bridge.rs).
  • FVK / UFVK - Full Viewing Key, Unified Full Viewing Key.

G​

  • g_d - Sapling diversifier base, derived from d.
  • Gitian - Deterministic build system for releases. See contrib/gitian-descriptors/.
  • Groth16 - Pairing-based zk-SNARK proof system. Used by Sprout (post-CVE) and Sapling.

H​

  • Halo 2 - The IPA-based zk-SNARK proof system used by Orchard.
  • hashAuthDataRoot - NU5 commitment to per-bundle auth data.
  • hashChainHistoryRoot - ZIP-221 history MMR commitment.
  • hashSaplingRoot - Sapling note commitment tree root.
  • Hash160 - RIPEMD160(SHA256(⋅))\mathsf{RIPEMD160}(\mathsf{SHA256}(\cdot)).
  • HD - Hierarchical Deterministic key derivation (BIP-32 / ZIP-32).
  • HRP - Human-Readable Prefix (Bech32).

I​

  • IMT - Incremental Merkle Tree. See src/zcash/IncrementalMerkleTree.hpp.
  • inv - "Inventory" message: announcement of an object by hash.
  • IPA - Inner-product argument; the polynomial commitment used by Halo 2.
  • ivk - Incoming Viewing Key (Sapling/Orchard).

J​

  • JoinSplit - The Sprout shielded transaction primitive: up to 2 input notes, up to 2 output notes, in one zk proof.
  • Jubjub - The in-circuit curve embedded in BLS12-381. Used by Sapling.

K​

  • KA - Key Agreement (Diffie-Hellman over Jubjub or Pallas).
  • KDF - Key Derivation Function.

L​

M​

  • mapBlockIndex - Map of block-header hash to CBlockIndex.
  • mapWallet - Wallet's map of transaction hash to CWalletTx.
  • MPC - Multi-Party Computation. Used to generate the Sprout/Sapling SRS.

N​

  • nBranchId / nConsensusBranchId - The branch ID a transaction is bound to.
  • nf / nullifier - Output of PRFnf\mathsf{PRF}^{\mathsf{nf}} applied to a note. A spent note reveals exactly one nullifier.
  • nk - Nullifier deriving key (Sapling).
  • NU - Network Upgrade. The Zcash term for a hard fork.
  • NU5 - The fifth network upgrade. Activates Orchard and v5 transactions.

O​

  • ock - Outgoing Cipher Key (Sapling).
  • Orchard - The post-NU5 shielded pool, on Halo 2.
  • out_ciphertext - Sender-facing note ciphertext (so the holder of the ovk can decrypt their own outgoing transactions).
  • Overwinter - The second NU. Introduced transaction expiry and branch IDs.
  • ovk - Outgoing Viewing Key.

P​

  • PoW - Proof of Work. Zcash uses Equihash (n,k)(n, k).
  • Pallas / Vesta - The Pasta cycle of curves used by Orchard.
  • peers.dat - Persistent addrman storage.
  • Pedersen hash - Bowe-Hopwood Pedersen in-circuit hash used by Sapling.
  • Poseidon - In-circuit hash used by some Orchard primitives.
  • pk_d - Diversified payment key (Sapling/Orchard).
  • PRF - Pseudorandom Function.

R​

  • rcm - Note commitment randomness (Sapling).
  • rcv - Value commitment randomness.
  • RedJubjub / RedPallas - Sapling and Orchard signature schemes.
  • regtest - The regression-test network. Low PoW, configurable activations.
  • rho - Per-note value used in nullifier derivation.
  • rk - Randomised verification key for a spend.
  • RPC - Remote Procedure Call. The JSON-RPC server in src/rpc/.
  • rseed - Sapling note randomness seed (post-ZIP-212).
  • rt - Note commitment tree root (the spend's anchor).

S​

  • Sapling - The second shielded pool. Groth16, BLS12-381, Jubjub.
  • secp256k1 - The transparent-layer curve. Two implementations in the tree: vendored src/secp256k1/ and the Rust secp256k1 crate.
  • Sinsemilla - The in-circuit hash used by Orchard.
  • SHA-256 - Hash used for txids (pre-NU5), block hashes, checksums.
  • sighash - The hash a transaction's signatures sign over. ZIPs 143, 243, 244, 225 define the per-NU variants.
  • sigcache - Cache of validated ECDSA signatures. See src/script/sigcache.cpp.
  • Sprout - The original shielded pool.
  • SPV - Simplified Payment Verification (light clients).
  • SRS - Structured Reference String (the Groth16 trusted setup output).

T​

  • tableRPC - The global dispatch table of RPC commands.
  • testnet - The public testnet. Frequently reset.
  • Tor v3 - The anonymity network. Supported via src/torcontrol.cpp.
  • turnstile - ZIP-209: net value flowing into a pool can be tracked, and unauthorised counterfeiting becomes detectable on the chain.

U​

  • UA / UVK / UFVK / UIVK - Unified Address / Viewing Key / Full VK / Incoming VK. See ZIP-316.
  • ufvk1..., uivk1..., u1... - Bech32m-encoded unified objects.
  • UTXO - Unspent Transaction Output (transparent only).

V​

  • v / valueBalance / valueBalanceSapling / valueBalanceOrchard - Net value moving out of a shielded bundle. Public.
  • vUpgrades - The activation table in src/consensus/params.h.
  • vFundingStreams - The per-NU funding-stream table. See ZIP-207.

W​

  • WalletTxBuilder - The modern shielded transaction builder. See src/wallet/wallet_tx_builder.h.
  • WIF - Wallet Import Format (transparent key encoding).

Z​

  • zcash_history - The Rust crate implementing the ZIP-221 MMR.
  • zcash_note_encryption - Rust crate for Sapling/Orchard note encryption.
  • zcash_primitives - Rust crate with Zcash types and consensus rules.
  • zcash_proofs - Rust crate for Sapling proving and Sprout verifying.
  • zebra / zebrad - The Zcash Foundation's Rust full-node implementation: github.com/ZcashFoundation/zebra.
  • ZIP - Zcash Improvement Proposal. See zips.z.cash.
  • ZIP-32 - HD key derivation for Sapling and Orchard.
  • ZIP-209 - Turnstile enforcement.
  • ZIP-225 - v5 transaction format.
  • ZIP-244 - NU5 transaction digests and sighash.
  • ZIP-316 - Unified Addresses and viewing keys.
  • ZK / zk-SNARK - Zero-Knowledge Succinct Non-interactive ARgument of Knowledge.
  • ZMQ - ZeroMQ; optional publisher in src/zmq/.

3. The code​

This is a glossary, not a chapter with its own implementation. Each term above links to the file where it lives.

4. Failure modes​

  • Using a term from this glossary in code without ensuring the reader will recognise it. Caught by review only. The glossary is here so contributors can include only well-known terms in code comments and link unknown ones.
  • Glossary drift. If a term is renamed in code, the link here rots. Run a periodic link-check.

5. Spec pointers​

  • The Zcash Protocol Specification has its own glossary in section 1.4. This chapter complements but does not replace it.
  • The librustzcash repositories use the same vocabulary; their documentation comments are authoritative for any term defined there.

6. Exercises​

  1. Spot a missing term. Pick five terms from src/consensus/upgrades.cpp that are not in this glossary. Either find them in the spec or open an issue.

  2. Cross-check. For one entry above, follow the link and verify the term is actually defined there. (This is a maintenance task masquerading as an exercise.)

  3. Annotate a transaction. Decode a v5 testnet transaction using zcash-inspect. Identify every named field (e.g. cv, nf, rk, cmx, enc_ciphertext, out_ciphertext, valueBalanceOrchard, bindingSig). Cross-check each against this glossary.

7. Further reading​