Glossary
Every term these pages use, in a sentence or two, with a link to the page that explains it. Blockchain and engineering terms link to the learning path; crypto-aio's own terms link to Core concepts or the Developer tour.
A · B · C · D · E · F · G · H · I · J · K · L · M · N · O · P · Q · R · S · T · U · V · W · X
A
Account model
Keeping a balance per address, as Ethereum, Tron, Solana and TON do. Compare UTXO. Lesson 7.
Address
A shareable name for an account, computed from a public key in a format each chain defines. In crypto-aio, an Address object has a canonical and a display form. Lesson 3.
Address lease
A short, renewable lock on one sending address, held while an ordering slot is reserved and signed, so concurrent transfers get distinct nonces. Stop 5.
Ambiguous
An error after which nobody can know whether the action happened, such as a lost reply to a broadcast. error.ambiguous === true: retry with the same idempotency key, never a new one. Lesson 10.
API key
A secret that identifies your account with a provider; often part of the endpoint URL. Wrap it in secret(). Lesson 9.
Archive node
A node that keeps the chain's state at every past block, needed for some historical proofs. Lesson 9.
Asset, asset id
What a transfer moves: a native coin or a token. An asset id such as ethereum:mainnet/erc20:0x… names it on one chain and network. Lesson 4.
At-least-once delivery
Retrying until acknowledged, so a message may arrive twice; safe with idempotent processing. Scanners deliver blocks this way. Lesson 11.
Attempt
One signed transaction for an Operation, stored before it is broadcast and never changed. Replacements, cancels and rebuilds add Attempts. Stop 3.
B
Backoff
Waiting longer between each retry (200 ms, 400 ms, 800 ms, …), with some randomness (jitter). Lesson 10.
Bandwidth, energy
Tron's resources: bandwidth pays for a transaction's size, energy for contract execution, either from staked TRX or burned TRX. Tron networks.
Base fee
The part of an EIP-1559 fee set by the protocol from recent demand, and burned. Lesson 8.
Base unit
An asset's smallest unit (satoshi, wei, lamport, sun, nanogram). Amounts are whole numbers of base units. Lesson 4.
Batch transfer
One transaction that pays several outputs, on chains with the batch-transfer capability. Send a transfer.
BIP32, BIP39, BIP44
Bitcoin standards reused across chains: hierarchical key derivation, mnemonic phrases, and the m/44'/coin'/account'/change/index path layout. Lesson 3.
Block, block height, block hash
A batch of transactions with a header; its position in the chain; the hash that identifies it and that the next block links to. Lesson 6.
Broadcast
Sending a signed transaction's raw bytes to a node, which passes it to the network. Lesson 5.
C
Capability
A named feature a handle may have, such as tokens or replace-fee; bc.supports(name). Capabilities.
Chain, network, library
A blockchain (ethereum), one of its deployments (mainnet, sepolia), and the SDK used for it (ethers). A handle is bound to one of each. Core concepts.
Chain family
Chains that share a design and a driver, such as the EVM family. Stop 2.
Chain id
A number that identifies an EVM network (1 for Ethereum mainnet), signed into every transaction so it cannot be replayed on another chain. Lesson 5.
Change
The output of a UTXO transaction that returns the remainder to the sender. Lesson 7.
Circuit breaker
Stops sending to a failing endpoint for a while (failureThreshold, openMs). Lesson 10.
Claim
A worker's expiring, fenced lease on one Operation. Stop 4.
Coin selection
Choosing which UTXOs a transaction spends. Lesson 7.
Cold wallet
Keys kept offline, signing by hand. Lesson 3.
Confirmations
The blocks on top of a transaction's block, its own included. Lesson 6.
Consensus
How a network's nodes agree on one history: proof of work, proof of stake, and others. Lesson 6.
Container
CryptoAio: owns configuration, stores, signers, hooks, plugins, the driver pool and events. One per tenant. Stop 1.
Contract suites
Tests from crypto-aio/testing that a store implementation must pass. Write a durable store.
Cursor
A scanner's durable position, moved only when you ack() an event. Stop 7.
Custody
How and where private keys are held and used: hot wallets, HSMs, KMS, MPC, cold storage. Lesson 15.
D
Decimals
How many digits of an asset's amount sit after the decimal point. Lesson 4.
Deposit
A transfer to one of your addresses, made by someone else; read, not proven. Receive deposits.
Derivation path
The path in an HD key tree that picks one key, such as m/44'/60'/0'/0/0. Lesson 3.
Double spend
Spending the same money twice; what a ledger, and finality, exist to prevent. Lesson 1.
Driver
The code that speaks one chain family's language, behind the core's ports. Loaded on first use. Stop 2.
Dropped
A transaction no healthy endpoint has seen for a while. Never terminal: the workers resend it. Stop 4.
E
ECDSA, Schnorr, EdDSA
Signature algorithms: ECDSA and Schnorr on secp256k1 (Bitcoin, EVM, Tron), EdDSA on ed25519 (Solana, TON). Lesson 2.
EIP-1559
Ethereum's fee design: a protocol base fee plus a priority tip, capped by a maximum fee per gas. Lesson 8.
Endpoint
One URL of a provider: an RPC node or an indexer. Lesson 9.
ERC-20, TRC-20, SPL, jetton
The token standards of the EVM chains, Tron, Solana and TON. Lesson 4.
Esplora
The REST API, run by mempool.space, blockstream.info or yourself, that the Bitcoin family reads. Bitcoin networks.
Evidence
What a status rests on: observed (one endpoint's view) or proven (finalized data, agreed by a quorum). Stop 6.
EVM
The Ethereum Virtual Machine, and the family of chains that share its design: Ethereum, BNB Smart Chain, Polygon, the Avalanche C-Chain, Arbitrum, Optimism, Base. EVM networks.
Expiry
A deadline after which a transaction can never land (Tron, Solana); proven expiry lets rebuild re-issue it. Lesson 7.
Extended public key (xpub)
See xpub.
F
Fee market
Competition for block space that sets the fee needed to be included soon. Lesson 8.
Fencing token
A number that grows with every new lease; storage refuses writes that carry an older one. FENCING. Lesson 13.
Finality, final
The point after which a transaction can never be undone: probabilistic (deep enough) or deterministic (finalized). Lesson 6.
Finalized tag
An EVM block tag that names the newest finalized block (finality-tag). EVM networks.
G
Gas, gas limit
A unit of EVM computation; the most a transaction may use. A failed call still pays its gas. Lesson 8.
Genesis block
The first block of a chain; its hash identifies the network. Lesson 6.
H
Handle
Blockchain: an immutable object bound to one chain, network, library, provider set and wallet, that you call methods on. Stop 1.
Hash
A fixed-size fingerprint of data: deterministic and one-way. Lesson 2.
HD wallet
A hierarchical deterministic wallet: a tree of keys derived from one secret. Lesson 3.
Hot wallet
Keys on an online server, for automatic payouts. Lesson 3.
HSM, KMS
A hardware security module, or a cloud key management service: signs on request, never exports the key. Lesson 15.
I
Idempotency, idempotency key
Doing something twice has the effect of doing it once; the caller's unique id for one payment that makes retries safe. Lesson 11.
Included
In a block, but not final yet. Lesson 6.
Indexer
A service that answers history questions (an address's transactions) from its own database. Lesson 9.
Intent, intentHash
What you want to happen ({ to, amount, … }); a hash of its normalized form, compared when an idempotency key repeats. Lesson 11.
J
JSON-RPC
A protocol for calling a server's named methods with JSON, used by EVM and Solana nodes. Lesson 9.
K
Key pair
A private key and the public key computed from it. Lesson 2.
L
Lagging endpoint
An endpoint more than maxLagBlocks behind the best known height; it decides nothing. Lesson 14.
Lease
A lock that expires unless renewed. Lesson 13.
Ledger
A record of accounts, balances and every change. Lesson 1.
M
Mainnet, testnet
The network with real money; a network with free coins for testing. Lesson 1.
Masterchain
TON's coordinating chain; a transaction is final once a masterchain block includes it. TON networks.
Memo
A public note attached to a transaction, on chains with the memo capability. Lesson 5.
Mempool
Where valid transactions wait until a block includes them. Lesson 5.
Mnemonic
Words that encode the master secret of an HD wallet (BIP39). Lesson 3.
MPC, multisig
Signing that needs several parties (multi-party computation) or several keys. Lesson 15.
N
Namespace
A container's prefix for every store key; one per tenant. Configuration.
Native coin
The coin a chain's own rules count, which also pays its fees: ETH, BTC, TRX, SOL, Gram, AVAX. Lesson 4.
Node
A server that runs a chain's software and keeps a copy of its ledger. Lesson 9.
Nonce, nonce gap
An account's transaction counter (EVM); a missing nonce that blocks later transactions (nonce.gap). Lesson 7.
O
Observed
Evidence from one endpoint's current view; it can change. Stop 6.
Operation
One payment as a stored business record, unique per idempotency key, with a state and an outcome. Stop 3.
Ordering slot
What orders a wallet's transactions: a nonce, a seqno, a set of inputs or an expiry. Reserved per Operation. Stop 5.
P
Plugin
SDK-free data that adds chains, networks, assets, presets and adapters. Write a chain family plugin.
Preset
A provider recipe, such as alchemy or trongrid, that turns an API key into endpoints. Networks.
Priority fee (tip)
The part of a fee that goes to the block producer. Lesson 8.
Private key, public key
The secret that controls funds; the shareable key computed from it. Lesson 2.
Proof quorum, proven
The number of endpoints that must agree on a proof read (proofQuorum, 2); evidence from finalized data under that quorum. Stop 6.
Provider
A named set of endpoints: a preset with a key, or your own URLs. Lesson 9.
PSBT
A partially signed Bitcoin transaction: the format hardware wallets sign. Cold and asynchronous signing.
Q
Quorum read
A read accepted only when enough independent endpoints agree. Lesson 14.
R
Rate limit
A cap on how many requests a client may send; 429 Too Many Requests when exceeded. Lesson 9.
Raw transaction
A signed transaction's bytes, ready to broadcast. Lesson 5.
Rebroadcast, replace, cancel, rebuild
Resend the same bytes; a new Attempt in the same slot with a higher fee; a conflicting self-transfer; re-issue after proven expiry. Fix a stuck transfer.
Receipt
An EVM transaction's result: success or failure, and the events it logged. Lesson 6.
Recovery
aio.operations.recover(): finishing in-flight work after a restart, without signing. Stop 4.
Redaction
Replacing a secret with [REDACTED] before any output. Lesson 15.
Reorg, reorg window, rollback
The network replacing its newest blocks; how many blocks a scanner keeps to detect it; the scanner event that reports it. Lesson 6, Stop 7.
Retry class
How a request may be retried: safe, ambiguous-on-failure or never-auto. Stop 6.
RPC
A remote procedure call: calling a server's named method over the network. Lesson 9.
S
sat/vB
Satoshis per virtual byte: Bitcoin's fee rate. Lesson 8.
Scanner
bc.scanner(): reads blocks in order for deposits, with a durable cursor and rollbacks. Stop 7.
Scope
aio.scope(): inherits and overrides a container's configuration, sharing its stores; not a tenant boundary. Stop 1.
Secret
A value whose disclosure causes harm; in crypto-aio, a Secret wrapper that prints as [REDACTED]. Lesson 15.
secp256k1, ed25519
The two elliptic curves in use: secp256k1 for Bitcoin, EVM, Tron and Avalanche; ed25519 for Solana and TON. Lesson 2.
Seqno
A TON wallet contract's message counter. Lesson 7.
Signature, signature scheme
Proof that a private key approved one exact message; the exact recipe a chain expects (secp256k1-ecdsa, secp256k1-schnorr, ed25519). Lesson 2.
Signer, signing request
The only place keys live (localSigner, callbackSigner); what the library asks it to sign. Stop 8.
Smart contract
A program stored and run on a blockchain. Lesson 4.
Solidified
Tron's finalized block, about 19 blocks below the head. Tron networks.
Stalled
An Operation a node refused, whose bytes may still land. Not a failure: rebroadcast, replace or cancel it. Fix a stuck transfer.
Stores
OperationStore, LockManager, SequenceStore and CursorStore: where crypto-aio keeps its state. Write a durable store.
T
Timeout
The deadline after which a client stops waiting. Lesson 10.
Token
A balance kept by a smart contract. Lesson 4.
Transaction, transaction hash
A signed instruction to change the ledger; its id, usually the hash of its signed bytes. Lesson 5.
Transport
crypto-aio's own HTTP layer under every driver: timeouts, retries, rate limits, health checks, quorum reads, redaction. Stop 6.
U
UTXO
An unspent transaction output: a coin on a UTXO chain (Bitcoin, the Avalanche X-Chain and P-Chain), spent whole as an input. Lesson 7.
V
Version (optimistic concurrency)
A number on each stored record; an update that expects an older one fails (VERSION_CONFLICT). Lesson 12.
W
Wallet
Whatever holds the keys that sign for an account. In crypto-aio, a named configuration that says which key sends. Lesson 3.
Watch-only
A wallet with public information only: it reads, and with a publicKey it can prepare unsigned transactions, but it never signs. Lesson 3.
Wei, satoshi, lamport, sun, nanogram
The base units of ETH, BTC, SOL, TRX and Gram. Lesson 4.
Workers
Background loops (aio.monitor.start()) that follow every Operation to a verdict. Stop 4.
Write-ahead
Recording an intended change durably before acting on it; crypto-aio stores each signed transaction before broadcasting it. Lesson 12.
X
X-Chain, P-Chain, C-Chain
Avalanche's exchange chain (UTXO), platform chain (UTXO, staking) and contract chain (EVM). Avalanche X-Chain and P-Chain.
xpub
An extended public key: derives child addresses without any private key. Lesson 3.