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This guide demonstrates how to create, sign, and broadcast a transaction using the Adamik API along with the common Bitcoin library, bitcoinjs-lib. This tutorial is perfect for developers who want to integrate Adamik’s features into their Bitcoin workflows, ensuring secure and efficient transaction management.

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Prerequisites

  • Node.js and npm installed
  • Basic understanding of Bitcoin and transaction workflows
  • Familiarity with the bitcoinjs library

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Step-by-Step Guide

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1. Setting Up the Environment

Ensure you have the bitcoinjs library installed in your project: 
npm install bitcoinjs-lib
In this example, we’ll start with just the mnemonic and derive a typical HD wallet. For that, we’ll require bip32 and bip39 libraries: 
npm install bip32 bip39
Finally, because we’ll be using deriving a Taproot account for this example, you’ll also need a elyptic curve cryptographiy library (ECC): 
npm install @bitcoinerlab/secp256k1

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2. Writing the Script

https://github.com/bitcoin/bips/blob/master/bip-0086.mediawiki Below is the script that handles the full transaction flow, from creating a wallet to broadcasting the signed transaction. 
import * as ecc from "@bitcoinerlab/secp256k1";
import BIP32Factory from "bip32";
import * as bip39 from "bip39";
import * as bitcoin from "bitcoinjs-lib";
import { toXOnly } from "bitcoinjs-lib/src/psbt/bip371";

bitcoin.initEccLib(ecc);

const bip32 = BIP32Factory(ecc);

// Replace with your wallet's mnemonic phrase
const mnemonic = "";
// Fill in your derivation path for Taproot (BIP-86)
// This script is setup as if this account has 1 simple UTXO of more than 100000 sats
const path = `m/86'/0'/0'/0/0`;
const recipientAddress = ""; // recipient of your choice, sender if none
const ADAMIK_API_KEY = ""; // Adamik API key

async function main() {
  // Create wallet using mnemonic phrase
  const seed = await bip39.mnemonicToSeed(mnemonic);
  const rootKey = bip32.fromSeed(seed);
  const childNode = rootKey.derivePath(path);
  const internalPubkey = toXOnly(childNode.publicKey);
  const { address } = bitcoin.payments.p2tr({
    internalPubkey,
  });

  console.log("public address of sender:", address);

  // Prepare the transaction request
  const requestBody = {
    transaction: {
      data: {
        chainId: "bitcoin", // Target Bitcoin
        mode: "transfer", // Simple tx
        sender: address,
        recipient: recipientAddress || address,
        amount: "10000", // Transaction amount in satoshis
      },
    },
  };

  // Encode the transaction with Adamik API
  const responseEncode = await fetch(
    "https://api.adamik.io/api/bitcoin/transaction/encode",
    {
      method: "POST",
      headers: {
        Authorization: ADAMIK_API_KEY,
        "Content-Type": "application/json",
      },
      body: JSON.stringify(requestBody),
    }
  );

  const encodedData = await responseEncode.json();
  console.log("encodedData:", encodedData);
  const rawtx = encodedData.transaction.encoded;

  // Create and sign the PSBT (Partially Signed Bitcoin Transaction)
  const psbt = bitcoin.Psbt.fromHex(rawtx);
  psbt.updateInput(0, {
    tapInternalKey: internalPubkey,
  });

  const tweakedChildNode = childNode.tweak(
    bitcoin.crypto.taggedHash("TapTweak", internalPubkey)
  );
  psbt.signTaprootInput(0, tweakedChildNode);

  psbt.finalizeAllInputs();
  const signedTransaction = psbt.extractTransaction().toHex();

  // Prepare to broadcast the signed transaction
  const sendTransactionBody = {
    transaction: {
      data: encodedData.transaction.data,
      encoded: encodedData.transaction.encoded,
      signature: signedTransaction,
    },
  };

  // Broadcast the transaction using Adamik API
  const responseBroadcast = await fetch(
    "https://api.adamik.io/api/bitcoin/transaction/broadcast",
    {
      method: "POST",
      headers: {
        Authorization: ADAMIK_API_KEY,
        "Content-Type": "application/json",
      },
      body: JSON.stringify(sendTransactionBody),
    }
  );

  const responseData = await responseBroadcast.json();
  console.log("Transaction Result:", JSON.stringify(responseData));
}

main();

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3. Explanation

  • Wallet Creation: The script begins by creating a wallet using a mnemonic phrase, which is crucial for managing private keys. Please note Adamik API doesn’t have the custody of the assets.
  • Transaction Encoding: The transaction details are passed to the Adamik API, which translates them into a raw transaction to be signed.
  • Signing and Broadcasting: The transaction is then signed with the wallet’s private key and finally broadcast to the Bitcoin network using the Adamik API.

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4. Troubleshooting

  • Invalid API Key: Ensure your Adamik API key is correct.
  • Network Issues: Verify network availability and Adamik API status.
  • Security Note: Never hardcode sensitive information like mnemonic phrases in your production environment.

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5. Get in Touch

Connect with us through our Discord Server or direclty through GitHub.