Use Imported BTC Wallets

Learn how to work with imported Bitcoin wallets for common operations like checking balances and signing transactions

Overview

This guide shows you how to work with imported Bitcoin wallets for common operations. Once you’ve imported a private key, you can perform various wallet operations directly.

Prerequisites

• Imported a Bitcoin private key
• Set up your authenticated client
• Installed Bitcoin dependencies

Step 1: Check Wallet Balance

Check the Bitcoin balance of your imported wallet using a block explorer API:

const address = 'bc1q...your-imported-wallet-address';

// Using Blockstream API
const response = await fetch(
  `https://blockstream.info/api/address/${address}`
);
const data = await response.json();

const balanceSats = data.chain_stats.funded_txo_sum - data.chain_stats.spent_txo_sum;
const balanceBtc = balanceSats / 100_000_000;

console.log('Balance:', balanceSats, 'satoshis');
console.log('Balance in BTC:', balanceBtc);

Step 2: Get UTXOs for Your Wallet

Before sending transactions, you need to fetch available UTXOs:

const address = 'bc1q...your-imported-wallet-address';

// Fetch UTXOs using Blockstream API
const response = await fetch(
  `https://blockstream.info/api/address/${address}/utxo`
);
const utxos = await response.json();

console.log('Available UTXOs:', utxos);
// Output: [{ txid: '...', vout: 0, value: 50000, status: {...} }, ...]

Step 3: Sign Transactions with Imported Wallet

Use your imported wallet to sign Bitcoin transactions:

import * as bitcoin from 'bitcoinjs-lib';
import { BitcoinNetwork } from '@dynamic-labs-wallet/core';

const btcClient = await authenticatedBtcClient();
const walletAddress = 'bc1q...your-imported-wallet-address';

// Create PSBT with your UTXO
const psbt = new bitcoin.Psbt({ network: bitcoin.networks.bitcoin });

// Add input from your wallet
psbt.addInput({
  hash: 'previous_txid',
  index: 0,
  witnessUtxo: {
    script: bitcoin.address.toOutputScript(walletAddress, bitcoin.networks.bitcoin),
    value: 50000, // satoshis
  },
});

// Add output
psbt.addOutput({
  address: 'bc1q...recipient-address',
  value: 40000, // satoshis (minus fee)
});

// Sign with imported wallet
const signedPsbt = await btcClient.signTransaction({
  transaction: psbt.toBase64(),
  senderAddress: walletAddress,
  network: BitcoinNetwork.MAINNET,
});

console.log('Signed PSBT (base64):', signedPsbt);

Step 4: Sign Messages with Imported Wallet

Sign messages for authentication or data integrity:

import { BitcoinNetwork } from '@dynamic-labs-wallet/core';

const message = 'Hello from my imported Bitcoin wallet!';
const signature = await btcClient.signMessage({
  message,
  accountAddress: 'bc1q...your-imported-wallet-address',
  network: BitcoinNetwork.MAINNET,
});

// Returns BIP-322 signature in base64 format
console.log('Message signed (base64):', signature);

Complete Example: Sign and Send from Imported Wallet

import * as bitcoin from 'bitcoinjs-lib';
import { BitcoinNetwork } from '@dynamic-labs-wallet/core';

export const signAndSendFromImportedWallet = async ({
  walletAddress,
  recipientAddress,
  amountSats,
  feeSats,
}: {
  walletAddress: string;
  recipientAddress: string;
  amountSats: number;
  feeSats: number;
}) => {
  const btcClient = await authenticatedBtcClient();
  const network = bitcoin.networks.bitcoin;

  // Step 1: Fetch UTXOs
  const utxoResponse = await fetch(
    `https://blockstream.info/api/address/${walletAddress}/utxo`
  );
  const utxos = await utxoResponse.json();

  if (utxos.length === 0) {
    throw new Error('No UTXOs available');
  }

  // Step 2: Select UTXOs (simple selection - use first one)
  const utxo = utxos[0];

  // Step 3: Create PSBT
  const psbt = new bitcoin.Psbt({ network });

  psbt.addInput({
    hash: utxo.txid,
    index: utxo.vout,
    witnessUtxo: {
      script: bitcoin.address.toOutputScript(walletAddress, network),
      value: utxo.value,
    },
  });

  // Add recipient output
  psbt.addOutput({
    address: recipientAddress,
    value: amountSats,
  });

  // Add change output if needed
  const change = utxo.value - amountSats - feeSats;
  if (change > 546) { // Dust threshold
    psbt.addOutput({
      address: walletAddress,
      value: change,
    });
  }

  // Step 4: Sign
  const signedPsbtBase64 = await btcClient.signTransaction({
    transaction: psbt.toBase64(),
    senderAddress: walletAddress,
    network: BitcoinNetwork.MAINNET,
  });

  // Step 5: Finalize and extract
  const signedPsbt = bitcoin.Psbt.fromBase64(signedPsbtBase64);
  signedPsbt.finalizeAllInputs();
  const rawTx = signedPsbt.extractTransaction().toHex();

  // Step 6: Broadcast
  const broadcastResponse = await fetch('https://blockstream.info/api/tx', {
    method: 'POST',
    body: rawTx,
  });

  const txid = await broadcastResponse.text();
  console.log('Transaction broadcasted:', txid);
  return txid;
};

List All Bitcoin Wallets

Get all Bitcoin wallets associated with your account:

const btcWallets = await btcClient.getBitcoinWallets();

console.log('Bitcoin wallets:', btcWallets.length);
btcWallets.forEach(wallet => {
  console.log(`- ${wallet.accountAddress} (${wallet.chainName})`);
});

Best Practices

1. Balance Checking: Verify sufficient balance before sending transactions
2. UTXO Management: Select UTXOs efficiently to minimize fees
3. Fee Estimation: Use current fee rates from mempool APIs
4. Error Handling: Implement proper error handling for all wallet operations
5. Security: Never expose sensitive information in server-side code
6. Network Selection: Use testnet for development and testing

Fee Estimation

Estimate appropriate fees before sending:

// Fetch recommended fee rates
const feeResponse = await fetch('https://blockstream.info/api/fee-estimates');
const feeEstimates = await feeResponse.json();

// feeEstimates contains sat/vB for different confirmation targets
// e.g., { "1": 25, "3": 15, "6": 10 } means:
// - 25 sat/vB for ~1 block confirmation
// - 15 sat/vB for ~3 block confirmation
// - 10 sat/vB for ~6 block confirmation

// For Native SegWit P2WPKH: ~110 vBytes for 1-in-1-out tx
const estimatedFee = feeEstimates["3"] * 110; // sat for ~3 block confirmation

Next Steps

• Sign Bitcoin transactions
• Sign Bitcoin messages