Glossary

Cardano-specific terminology used throughout this manual and the code.

Cryptography

Blake2b-224 — 28-byte hash function. Used for pool key hashes, script hashes, addresses (key portion).

Blake2b-256 — 32-byte hash function. Used for transaction IDs, block IDs, header hashes, script context digests.

BLS12-381 — Pairing-friendly elliptic curve. Used by Plutus V3 builtins (Bls12_381_G1_*, Bls12_381_G2_*, Bls12_381_MillerLoop, FinalVerify) per CIP-0381.

Ed25519 — Edwards-curve signature scheme. Used for transaction witnesses, OpCert signatures, KES leaf signatures.

KES (Key Evolving Signature) — A signature scheme that periodically destroys old signing keys so a compromise of the current key cannot forge past blocks. Yggdrasil uses Sum-KES with depth 6 (62 evolutions). On mainnet a KES key is valid for ~90 days.

OpCert (Operational Certificate) — A signed certificate from the cold key authorising the KES key to forge blocks for a window of slots. Sequence number must monotonically increase per pool.

VRF (Verifiable Random Function) — Provides each block with a verifiable pseudo-random value used for both leader election and the per-block contribution to the epoch nonce.

Consensus and chain

Active slot coefficient (f) — Probability that any given slot has at least one block. Mainnet: 0.05. So roughly 1 in 20 slots produces a block.

Cardano Era — A protocol version with its own ledger format. In order: Byron, Shelley, Allegra, Mary, Alonzo, Babbage, Conway. Era boundaries are hard forks; a chain is the sequence of all eras’ blocks.

ChainDB — Yggdrasil’s chain database: immutable region (stable blocks, append-only) + volatile region (recent K blocks, may roll back) + ledger snapshots (periodic state checkpoints).

ChainSync — One of the five mini-protocols. Used to follow a peer’s chain: client requests next header or next rollback. State machine: MsgFindIntersect, MsgRequestNext, MsgRollForward, MsgRollBackward, MsgAwaitReply.

Epoch — A unit of time during which stake distribution and protocol parameters are fixed. Mainnet: 432,000 slots = 5 days.

Epoch boundary — The slot where one epoch ends and the next begins. Triggers stake snapshot rotation, reward calculation, and a number of book-keeping operations.

Fork — Two competing chains with a common ancestor. Resolved by the chain-selection rule (longer chain wins, with VRF-based tiebreakers).

Genesis — The initial chain state. For each era there is a genesis JSON: Byron, Shelley, Alonzo, Conway. Yggdrasil hashes each at startup and verifies against pinned values.

Hard fork — An era transition. Coordinated by an on-chain proposal in the previous era’s governance system.

Header — Block metadata: slot, prev hash, body hash, VRF, KES signature, OpCert. ChainSync ships headers; BlockFetch ships bodies.

Immutable region — Blocks past the security parameter k from the current tip. By assumption (Praos liveness), these will not roll back.

Praos — The Ouroboros protocol variant Cardano runs since the Shelley era. Successor to TPraos. Uses VRF leader election plus epoch-nonce evolution.

Roll forward — Apply the next block in chain order.

Roll backward — Undo recent blocks because the peer’s chain has switched to a different fork.

Security parameter (k) — Mainnet: 2160. Beyond 3k/f slots, the chain is considered final.

Slot — One second of network time. Slot 0 corresponds to the network’s epoch start time (preset-specific). Mainnet slot 0 = 2017-09-23 21:44:51 UTC.

Slot leader — The node entitled to produce a block in a given slot, determined by VRF on the slot index plus the epoch nonce, weighted by stake.

Stable block — A block in the immutable region. In Yggdrasil’s storage model, stable blocks live in the immutable store.

TPraos — The “Transitional Praos” protocol used in the Shelley era. Replaced by Praos in Babbage.

Volatile region — The most recent K=2160 blocks, which may roll back if the chain switches forks.

Network

Bootstrap peer — IOG-curated entry point used to seed peer discovery. Defined in topology.json.

Big-ledger peer — A peer from the largest stake pools, used as a high-quality discovery source during bootstrap or recovery.

Cold peer — A known peer with no current connection.

ConnectionManager (CM) — The component that tracks the lifecycle of every connection (inbound + outbound), handles graceful shutdown, and applies rate limits.

DataFlow — Per-connection mode: Unidirectional (one-way) or Duplex (both directions over the same TCP socket — saves a connection slot).

Diffusion mode — Per-local-root setting: InitiatorAndResponderDiffusionMode (full duplex) or InitiatorOnlyDiffusionMode (outbound only — used by block producers behind NAT).

Established peer — Has an active TCP connection and completed handshake.

Governor — The component that decides which peers to promote or demote among cold/warm/hot states. Its decisions are translated into CmActions and applied by the connection manager.

Hot peer — Active for sync (ChainSync + BlockFetch). Subset of warm.

Inbound governor — Per-connection state machine for inbound peers, mirroring upstream Ouroboros.Network.InboundGovernor.

Ledger peer — A peer learned from on-chain stake-pool relay registrations. Activated via useLedgerAfterSlot.

Local root — A peer the operator manually configured. Trusted, prioritised in sensitive mode.

Mini-protocol — One of five sub-protocols multiplexed over a connection: ChainSync (2), BlockFetch (3), TxSubmission (4), KeepAlive (8), PeerSharing (10).

Mux — The multiplexer that fairly schedules egress traffic across mini-protocols on a single TCP socket.

NtN (Node-to-Node) — Inter-node protocol, runs over TCP. Bootstrap, ChainSync, BlockFetch, TxSubmission, KeepAlive, PeerSharing.

NtC (Node-to-Client) — Local-only protocol over a Unix socket. LocalStateQuery, LocalTxSubmission, LocalTxMonitor. Used by wallets and cardano-cli.

PeerSharing — Mini-protocol 10. Lets neighbours exchange addresses of other peers.

Public root — A DNS-published root peer set, advertised by various community operators.

SDU — Service Data Unit. A fragment of a mini-protocol message. Mux fragments outgoing messages into SDUs of up to ~12 KiB.

Warm peer — Has an established connection but is not actively syncing.

Mempool and transactions

Mempool — Fee-ordered queue of pending transactions. Yggdrasil applies upstream’s per-peer byte budget (64 KiB), per-peer outstanding-TxIds cap (64), per-peer in-flight count cap (32), and a global aggregate byte budget (2 MiB).

TxId (Transaction ID) — Blake2b-256 of the transaction body CBOR.

TxSubmission2 — Mini-protocol 4. The pull-based flow where the local node advertises new TxIds and the peer pulls bodies for any unknown TxIds.

LocalTxSubmission — NtC protocol for submitting a transaction to the node’s mempool. Used by wallets.

LocalTxMonitor — NtC protocol for monitoring the mempool: list pending TxIds, get individual transactions, etc.

Ledger

DRep (Delegated Representative) — Conway-era governance entity. Stake holders delegate their voting power to DReps.

EnactState — The committed governance state at the start of an epoch. Pulled from the previous epoch’s ratified proposals.

Governance Action (GovAction) — A Conway-era proposal: ParameterChange, HardForkInitiation, TreasuryWithdrawals, NoConfidence, UpdateCommittee, NewConstitution, InfoAction.

LedgerState — Yggdrasil’s in-memory representation of the chain’s ledger state. Includes UTxO, pool state, account state, governance state, etc.

Plutus — Cardano’s smart contract platform. Three versions: V1, V2 (Babbage), V3 (Conway).

Pool key hash — Blake2b-224 of a pool’s cold key vkey. The on-chain identifier for a stake pool.

Stake credential — Either a key hash or a script hash that owns reward delegation rights.

Stake distribution — Per-pool aggregated active stake at the start of an epoch. Determines block-production probability.

UTxO (Unspent Transaction Output) — The atomic unit of state. A transaction consumes UTxOs and produces new ones.

Withdrawal — A reward-account-to-payment-account transfer signed by the stake credential’s witness.

Yggdrasil-specific

max_concurrent_block_fetch_peers — Operator knob. Default 2 (matches upstream bfcMaxConcurrencyBulkSync; graduated R258 based on R218 mainnet evidence showing 67% throughput delta). Set to 1 for strict single-peer audit/replay parity, or > 2 to push beyond the BulkSync cap on rich topologies.

ChainDb — The coordinated immutable + volatile + ledger-state storage facade in crates/storage.

FetchWorkerPool — Per-peer BlockFetch worker registry. Mirrors upstream Ouroboros.Network.BlockFetch.ClientRegistry.

HotPeerScheduling — Per-mini-protocol weight table for mux egress on hot peers. Defaults: BlockFetch=10, ChainSync=3, TxSubmission=2, KeepAlive=1, PeerSharing=1.

OutboundPeerManager — Yggdrasil’s runtime-side container for active outbound peer sessions. Owns the migrate-to-worker logic.

PeerSession — Per-peer state held by the runtime: TCP connection, mux handles, mini-protocol clients, KES heartbeat scheduler.

Tentative header — A header announced via MsgRollForward before its body has been validated. Yggdrasil supports this for diffusion pipelining (DPvDV).