API Documentation

This section outlines the mint and redeem request transaction structures for each network we support.

EVM Networks

Mint Request

function depositToken(
    IERC20 token, 
    uint256 amount, 
    uint destChainId, 
    string calldata recipientAddr
) public;

This function takes in an approved deposit token on the source chain from the user, which is then stored in a Bound smart contract vault, and results in a mint request for bUSD on the destination chain.

Field	Values	Description
token	contract address	the deposit token address (USDT, USDC, ...)
amount	int	amount of tokens to deposit in vault
destChainId	int	the destination chain ID to mint bUSD (BTC, OPNet, ...)
recipientAddr	string	the address to receive bUSD on the destination chain

Redeem Request (event)

event Withdrawal(address indexed to, IERC20 token, uint256 amount, string sourceTxId);

This event is emitted when an operator makes a withdrawal to process the bUSD redemption request that was submitted on Bitcoin.

Field	Values	Description
to	address	the recipient's address
token	contract address	the address of the token being redeemed (USDT, USDC, ...)
amount	int	the amount of tokens the recipient will receive
sourceTxId	string	the transaction hash of the redemption request that was submitted on the source chain

Bitcoin

Redeem request

This transaction structure allows users to make a bUSD redemption request for a supported stablecoin on a destination chain by transferring their bUSD Rune to the Bound Hot Wallet.

Input #	Description	Output #	Description
0	user's bUSD Rune UTXOs	0	bUSD Rune change UTXO sent to the user's address
1	user's BTC UTXOs	1	bUSD Rune UTXO sent to Bound's Hot Wallet address
		2	Bound Redeem Script
		3	Runestone OP_RETURN Script: send the amount of the redeemed bUSD Rune to Output 2
		4	BTC change UTXO sent to the user's address

Bound Redeem Script (output #2)

[OP_15 0x01 StableCoinId ReceiverBytes]

• OP_15: Bound Identity OP

• 0x01 (1 byte): the flag for redeem request

• StableCoinId (uint8 = 1 byte): the ID of the stablecoin the user wants to withdraw

  • you can get the StableCoinId of every supported stablecoin with this API:

    • [TESTNET] https://testnet-portal.bound.money/api/v1/tokens

• ReceiverBytes (the remain bytes): contains the user's EVM address, which is decoded from string to bytes (without prefix 0x)

Example Transaction

[explanation]

Input

• Input 0: user's bUSD Rune UTXO

  • used to redeem an equivalent amount of a stablecoin on the destination chain

• Input 1: user's BTC UTXO

  • used to pay transaction fee

Output

• Output 0: Rune change output

  • + Value: dust amount (‎546)

  • + PkScript: user's PkScript

• Output 1: bUSD Rune sent to Bound Hot Wallet

  • + Value: dust amount (‎546)

  • + PkScript: hotWallet's PkScript

• Output 2: Bound Redeem Script

  • + Value: dust amount (‎546)

  • + PkScript: OP_15 01 01 d21968dae95717c723e5c129db9eacc268e9ca44

    • *meaning the StableCoinId is 1 and the receiver address on the EVM chain is 0xd21968dae95717c723e5c129db9eacc268e9ca44

• Output 3: Runestone OP_RETURN with 1 edict:

  • {"Edicts":[{"ID":"BusdRuneId","Amount":"BusdAmount","Output":1}],"Pointer":0}

• Output 4: BTC change output

  • + Value: change amount (53978)

  • + PkScript: user's PkScript