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A

Address — A 20-byte identifier for a Quantum Chain account, displayed as 0x plus 40 hex characters. Derived from Keccak-256(publicKey)[0:20]. API key — A bearer token issued by Qustody that authenticates a service-to-service caller. Created via POST /v1/credentials, rotated via POST /v1/credentials/rotate. Approval — A signed acknowledgement from a user holding the approver role that a transaction may proceed. Required when a REQUIRE_APPROVAL policy rule matches. Audit log — A tamper-evident, hash-chained record of every state-changing API call. Verified via GET /v1/audit/verify. AML screening — Anti-money-laundering check performed against the destination address (and optionally the sender) before broadcast. Provided by Chainalysis or Shufti Pro.

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B

Bootnode — A discovery v4 node that helps new geth instances find peers. Run via build/bin/bootnode. Broadcast — Submitting a signed transaction to the Quantum Chain network via eth_sendRawTransaction. Returns a transaction hash.

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C

Callback signing mode — The signer integration mode where Qustody exposes a signing payload and waits for the signer to POST a signature back. Set with CUSTODY_SIGNER_TYPE=callback. Chain ID — The network identifier embedded in every signed transaction. 20803 for Quantum Chain mainnet. Circuit breaker — A reliability primitive in Qustody that opens after repeated failures to a downstream (signer, AML provider, RPC node), preventing cascade failures. Clique — The Proof-of-Authority consensus algorithm used by Quantum Chain. A fixed sealer set takes turns producing blocks. Confirmation — A block built on top of a transaction’s block. Qustody waits CUSTODY_CONFIRMATION_DEPTH confirmations (default 12) before marking a transaction CONFIRMED. Custody platform — A system that manages keys, policies, approvals, and audit on behalf of an organization. Qustody is the reference implementation for Quantum Chain.

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D

Devnet — A local development network. Typically a single Clique sealer with period=5. Digest — The 32-byte Keccak-256 hash that the post-quantum signer signs.

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E

Epoch — The interval at which a Clique chain finalizes its sealer set. 30000 blocks on Quantum Chain mainnet. EVM — Ethereum Virtual Machine. Quantum Chain runs the QVM, which inherits EVM bytecode, opcodes, and gas accounting but removes the ecrecover precompile and adds a post-quantum verification precompile at 0x0b. See QVM vs EVM. External signer — A separate process or service that holds private keys and produces signatures on demand. Required for production Qustody deployments.

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G

geth — The Quantum Chain reference client, a fork of go-ethereum. Built with make geth. gRPC signing mode — Qustody calls the signer over gRPC with mTLS. Set with CUSTODY_SIGNER_TYPE=grpc. Recommended for production.

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I

Idempotency key — A UUID provided by the caller in the Idempotency-Key header. Within 24 hours, repeating a request with the same key returns the original response without re-executing.

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K

Keystore — A JSON file containing an encrypted post-quantum private key (AES-128-CTR + PBKDF2). The file format matches the standard Web3 Secret Storage definition.

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M

Mempool — The pool of pending transactions held by each geth node before they’re sealed into a block. Mnemonic — A 12-word BIP-39 phrase that deterministically regenerates a post-quantum keypair. Generated by keygenerator; never stored on disk.

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N

Nonce — The sequential count of transactions sent from a given address. Quantum Chain (like Ethereum) requires nonces to be sequential. Non-custodial — The property that the platform never holds the user’s private keys. Qustody is non-custodial — keys live in the external signer.

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P

Policy — A rule set attached to a vault that constrains which transactions may proceed. Supported rules: MAX_AMOUNT, WHITELIST_ADDRESS, BLACKLIST_ADDRESS, REQUIRE_APPROVAL, TIME_WINDOW, DAILY_LIMIT. Post-quantum signature — A signature produced by a cryptographic scheme believed to be secure against quantum-capable adversaries. Used by Quantum Chain in place of ECDSA. Public key — The verification key paired with a post-quantum private key. Registered with Qustody when a wallet is created.

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Q

Quantum (QUANTUM) — The native currency of Quantum Chain. Quantum is to Quantum Chain what ETH is to Ethereum: it pays for gas and is the base unit of value transfer. Referenced in the Qustody API by asset_id: "QUANTUM". The smallest denomination is wei (1 QUANTUM = 10^18 wei). QRC token standard — A family of Quantum Chain token standards (QRC-20, QRC-721, QRC-1155, QRC-1400, QRC-3643, QRC-4626, QRC-3525) that mirror the operational shape of widely-used Ethereum-style standards while running on the QVM and being authorized with post-quantum signatures. See Token standards. QVM — Quantum Virtual Machine. The execution layer of Quantum Chain. EVM-compatible at the bytecode, opcode, and gas-accounting level, but the cryptographic primitives differ: ecrecover is removed and a post-quantum verification precompile is added at 0x0b. See QVM vs EVM. Qustody — The reference custody platform for Quantum Chain. Multi-tenant, non-custodial, policy-driven.

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R

RBAC — Role-Based Access Control. Qustody ships with five system roles (admin, operator, viewer, approver, compliance_officer) and supports custom roles. Reorg — A reorganization of the canonical chain when a longer fork is observed. Bounded in Clique by sealer-out-of-turn rules. Remote signing mode — Qustody calls the signer over HTTPS. Set with CUSTODY_SIGNER_TYPE=remote.

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S

Sealer — A validator in the Clique sealer set. Sealers take turns proposing blocks every period seconds. Signing payload — The data a signer must sign for a Qustody transaction: the transaction’s Keccak-256 digest, plus metadata (nonce, chain ID). Snap sync — The default geth sync mode. Downloads recent block headers and a state snapshot.

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T

Tenant — The top-level isolation boundary in Qustody. All resources (vaults, wallets, transactions, users, policies) are scoped to a tenant. Token (Qustody) — A Qustody-tracked record representing a deployed or to-be-deployed QRC token contract on Quantum Chain. Has an id, standard, symbol, decimals, contractAddress, status, adminVaultAccountId, and approvalPolicyId. See Token management. Token allowlist — An on-chain or off-chain list of addresses permitted to hold or transfer a permissioned QRC token. Maintained per token through the /v1/tokens/{tokenId}/allowlist endpoints. Token configuration — A draft of a token’s parameters stored in Qustody before deployment: standard, symbol, decimals, supply policy, admin vault, approval policy. Token operation — A single privileged action against a Qustody-managed token (DEPLOY_TOKEN, MINT, BURN, TRANSFER, GRANT_ROLE, REVOKE_ROLE, PAUSE, UNPAUSE, FREEZE, UNFREEZE, UPDATE_COMPLIANCE). Each operation flows through the existing transaction state machine and produces an audit-log entry. Token template — A pre-validated contract template that Qustody can instantiate for a chosen QRC standard. Listed via GET /v1/token-templates. Transaction state machine — The 14-state lifecycle a Qustody transaction moves through. See State machine. Travel rule — A regulatory requirement to share originator and beneficiary information with counter-party VASPs above a threshold. Supported by Qustody’s compliance endpoints.

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V

Vault — A logical grouping of wallets within a tenant. Policies attach to vaults. Validator — Synonym for sealer; a Quantum Chain node authorized to produce blocks.

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W

Wallet — A Qustody record representing a Quantum Chain address and its registered post-quantum public key. Created with POST /v1/wallets. Webhook — An HTTPS endpoint Qustody POSTs events to. Each delivery is signed with HMAC-SHA256 using the per-endpoint secret.