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. You can find the complete code example in the Adamik GitHub repository. 
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 = "your mnemonic phrase here";

// 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 derivationPath = `m/86'/0'/0'/0/0`;
// Replace with recipient address or leave empty for self-transfer
const recipientAddress = "";
// Replace with your Adamik API key from https://dashboard.adamik.io
const ADAMIK_API_KEY = "your-adamik-api-key";

async function main() {
  try {
    // Create wallet using mnemonic phrase
    const seed = await bip39.mnemonicToSeed(mnemonic);
    const rootKey = bip32.fromSeed(seed);
    const childNode = rootKey.derivePath(derivationPath);
    const internalPubkey = toXOnly(Buffer.from(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
          senderAddress: address,
          recipientAddress: recipientAddress || address,
          amount: "10", // Transaction amount in satoshis
        },
      },
    };

    console.log("Encoding transaction...");
    // 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(
      "Encoded transaction data:",
      JSON.stringify(encodedData, null, 2)
    );
    const rawtx = encodedData.transaction.encoded;

    console.log("Signing transaction...");
    // 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();
    console.log("Transaction signed");

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

    console.log("Broadcasting transaction...");
    // 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, null, 2));
    console.log("Transaction hash:", responseData.hash);
  } catch (error) {
    console.error("Error:", error);
  }
}

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 directly through GitHub.