A
Attestation A document signed by the AWS Nitro hardware that binds an enclave’s public key to the measurement (PCR0) of the code it runs. Anyone can use it to check that a signer key belongs to the published enclave code. See also: PCR0.B
BFA The RGB asset schema used for USDT on Bitcoin issued through the Utexo Mint. New supply is created by a bridge operation that must be backed by a finalized USDT0 deposit on Arbitrum, and a burn operation removes supply so the equivalent USDT0 can be released. Every recipient validates the EVM deposit behind each mint in the asset’s history. Bitcoin The base settlement layer used by Utexo. All RGB asset state is ultimately anchored to Bitcoin UTXOs, and Bitcoin provides double-spending prevention and final settlement guarantees. BIP-39 Bitcoin Improvement Proposal 39. The standard for generating human-readable mnemonic seed phrases (12 or 24 words) that can be used to derive all wallet keys. The Utexo SDK uses BIP-39 mnemonics for wallet initialisation and recovery. Blinded Invoice A privacy-preserving RGB payment request. The receiver generates a blinded UTXO reference that hides their address from the sender while still allowing the asset transfer to be verified client-side. Generated viawallet.blindReceive().
BtcRelay An Arbitrum contract that stores Bitcoin block headers and tracks the best chain by cumulative work. The BTC Relay service submits headers to it. The bridge checks a BtcRelay proof before releasing USDT0, and release signer enclaves check that their own header chain agrees with it.
Burn An RGB operation that destroys RGB USDT so the equivalent USDT0 can be released on Arbitrum. The EVM recipient and amount are committed in the burn and cannot be changed afterwards.
burnId The identifier the bridge derives from the RGB burn operation ID. The bridge stores it and rejects any release that reuses it.
C
CFA (Collectible Fungible Asset) An RGB asset type for tokens with a fixed supply cap per issuance batch. CFAs are used for assets such as limited-edition tokens; USDT on Bitcoin uses BFA. Unlike NIA assets, multiple CFA issuances can be made by the same issuer up to a defined global cap. Channel (Lightning) A bidirectional payment channel opened between two Lightning Network nodes. Channels allow off-chain USDT and BTC transfers with instant settlement. Utexo manages channel lifecycle, routing, and liquidity on behalf of integrators. Client-Side Validation The RGB protocol’s core security model. Instead of verifying asset state on a public blockchain, the recipient validates the full chain of ownership locally using cryptographic proofs. This preserves privacy and removes the need for global consensus on asset balances. Commitment A compact cryptographic hash anchored to a Bitcoin UTXO that represents off-chain RGB state. Commitments are indistinguishable from ordinary Bitcoin transaction metadata on-chain. Connector (Mint) A stateless gRPC microservice that monitors a specific blockchain’s smart contract forFundsIn events and issues FundsOut transactions on the destination chain. Each supported network has its own Connector implementation. All transfer state is held by the Mint orchestrator.
Consignment The data a sender hands to the receiver to prove an RGB transfer: the relevant contract history and state transitions. The receiver validates it before accepting the transfer.
E
EIP-712 An Ethereum standard for typed structured data signing. Release signer enclaves use EIP-712 to signfundsOut release messages for MultisigProxy, which verifies the M-of-N quorum on-chain.
Enclave Signer The signing service of the Utexo Mint. It runs inside an AWS Nitro Enclave, a hardware-isolated Trusted Execution Environment (TEE), and signs only after its own checks pass. It ships as two separate images: the mint signer, which signs the Bitcoin PSBT for a mint, and the burn (release) signer, which signs EVM releases. Signing keys are used only inside the enclave. The mint signer’s seed is generated by AWS KMS and stored encrypted, and only the enclave can decrypt it. Burn signers generate their keys inside the enclave. See also: Trusted Execution Environment (TEE).
F
FundsIn The bridge call and event used when a user locks USDT0 on Arbitrum for a mint. The deposit includes the RGB operation ID (OpId) of the prepared mint. The Mint Connector detects the event and notifies the Mint orchestrator. FundsOut The bridge call that releases USDT0 to the recipient after a validated RGB burn. An M-of-N quorum of release signer enclaves signs the release, andMultisigProxy calls fundsOut once the quorum is met.
H
HODL Invoice A Lightning invoice that does not immediately settle upon payment. The funds are held (“HODLed”) in a Hash Time-Locked Contract (HTLC) until the recipient explicitly accepts or the invoice expires. Used in atomic swap protocols and escrow flows to coordinate cross-chain payments.L
LayerZero The cross-chain messaging protocol that USDT0 uses to move between networks. The Utexo Mint uses it to bring USDT from Ethereum, Polygon PoS, Plasma, and Tron to Arbitrum, and to route releases onward. Lightning Invoice A standard BOLT-11 or BOLT-12 payment request used to receive BTC or RGB assets over Lightning channels. Generated viawallet.createLightningInvoice().
Lightning Network A Bitcoin Layer 2 payment protocol that enables instant, low-cost transfers via off-chain payment channels. RGB assets can move over Lightning channels on test networks; Lightning is not enabled on mainnet.
LDK (Lightning Development Kit) An open-source library by Spiral (Block) that implements the Lightning Network protocol in Rust. The Utexo RGB Lightning Node is built on top of LDK, enabling it to manage payment channels and route Lightning payments for RGB assets.
LSP (Lightning Service Provider) A node operator that provides channel liquidity and routing services to wallet users. Utexo acts as an LSP, opening inbound channels on behalf of users so they can receive Lightning payments without running their own node.
M
Mint (operation) An RGB operation that creates new RGB USDT. It is valid only if a matching, finalized USDT0 deposit on Arbitrum backs it. The mint signer signs the Bitcoin transaction that anchors it. Mint Connector See Connector (Mint). Mint orchestrator The central Mint coordinator. It tracks all in-flight transfers in a database, processes events from Connectors, and drives each transfer to completion or cancellation. Mnemonic A 12 or 24-word BIP-39 seed phrase that represents the root key of a wallet. Store it securely offline — it is the only way to recover a wallet. Never share it. MultisigProxy The Arbitrum contract that checks an M-of-N quorum of release signer signatures before it calls the bridge’sfundsOut. Its nonce protects against replayed releases.
N
NIA (Non-Inflationary Asset) An RGB asset type with a fixed total supply that cannot be inflated after issuance. Issued viawallet.issueAssetNia().
O
OpId (Operation ID) The identifier of an RGB operation. For a mint, the user includes the prepared mint’s OpId in the USDT0 deposit, which binds the deposit to that one mint. Mint status is tracked by OpId.P
PCR0 The measurement of the enclave image, reported in its attestation. The enclave code builds reproducibly, so anyone can rebuild it and compare PCR0. PSBT (Partially Signed Bitcoin Transaction) A standard format (BIP-174) for Bitcoin transactions that have not yet been fully signed. The Utexo SDK uses PSBTs as an intermediate step in the send flow, allowing keys to be held separately from transaction construction. The mint signer enclave signs the Bitcoin PSBT for EVM to RGB (mint) transfers. Signed viawallet.signPsbt().
R
Release signer federation The independent burn signer enclaves of the Utexo Mint. Each one validates the burn, the full RGB history, and the Bitcoin inclusion proofs. An M-of-N quorum of their signatures is required for every release. RGB A smart contract protocol built on Bitcoin that uses client-side validation. RGB enables the issuance and transfer of assets (such as USDT) natively on Bitcoin without modifying the Bitcoin protocol. Asset state is held off-chain; only cryptographic commitments are anchored on-chain. RGB Invoice A payment request specific to the RGB protocol. Contains the asset ID, expected amount, and a blinded or witness UTXO reference for the recipient. Used as the destination when minting USDT from Arbitrum to the Bitcoin RGB layer. Generated viawallet.blindReceive() or wallet.witnessReceive().
RGB Transport The communication layer used to exchange RGB state between sender and receiver during a transfer. The Utexo SDK connects to RGB proxy endpoints (e.g. rpcs://rgb-proxy-mainnet.utexo.com/json-rpc) to facilitate this exchange.
S
Single-Use Seal A core RGB primitive. A single-use seal binds an asset state transition to a specific Bitcoin UTXO, ensuring it can only be “opened” (spent) once. This prevents double-spending without requiring global ledger consensus. SPV (Simplified Payment Verification) Checking that a Bitcoin transaction is included in a block, and how deep it is, using block headers and a Merkle proof instead of the full chain. Release signer enclaves keep their own header chain from a pinned checkpoint to verify burns this way.T
TEE (Trusted Execution Environment) A hardware-isolated compute environment that provides confidentiality and integrity guarantees for the code and data running inside it. The Utexo Mint uses AWS Nitro Enclaves as its TEE. Code running in the enclave cannot be inspected or tampered with from the host operating system. See also: Enclave Signer. TUSDT A name used for the RGB-layer representation of USDT. The asset minted through the Utexo Mint is called USDT on Bitcoin in these docs and uses the BFA schema. See also: USDT (RGB).U
UDA (Unique Digital Asset) An RGB asset type for non-fungible tokens (NFTs) on Bitcoin. Each UDA has a unique token ID and represents a one-of-a-kind digital item. UDAs are issued and transferred using the RGB protocol with client-side validation. USDT (RGB) Tether’s USDT stablecoin issued natively on Bitcoin using the RGB protocol. Distinct from ERC-20 USDT (Ethereum) and TRC-20 USDT (Tron). RGB USDT is transferred on-chain with RGB and validated client-side. USDT0 Tether’s omnichain USDT, which moves between networks through LayerZero. The Utexo Mint locks USDT0 on Arbitrum to mint USDT on Bitcoin, and releases it after a burn. UTEXOWallet The primary class exported by the@utexo/rgb-sdk-rn and @utexo/rgb-sdk-web packages. It encapsulates wallet operations including initialization, asset transfers, Lightning invoice creation and payment, balance checking, and backup/restore. Node.js integrations use @utexo/wdk-rgb-lightning (WalletManagerRgbLightning) instead of UTEXOWallet.
UTXO (Unspent Transaction Output) A unit of Bitcoin that has been received but not yet spent. In RGB, UTXOs serve as anchors for asset state — each RGB asset allocation is bound to a specific UTXO.
V
VSS (Versioned Storage Service) A remote server that stores encrypted, versioned backups of wallet and Lightning node state, used by the Utexo SDKs and the RGB Lightning Node. Restoring from VSS still needs the wallet’s mnemonic.W
Witness Invoice An alternative to a blinded invoice for receiving RGB assets. Uses a witness UTXO reference rather than a blinded one. Less privacy-preserving than a blinded invoice but may be required in certain integration scenarios. Generated viawallet.witnessReceive().