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Getting Started

This guide will help you quickly set up and start using Shield for submitting private Bitcoin transactions.

Prerequisites​

Before using Shield, you should have:

  • Basic understanding of Bitcoin transactions
  • The ability to create and sign raw Bitcoin transactions
  • A tool or library capable of making HTTP requests (curl, request, axios, etc.)

Submit a transaction​

1. Get Shield Fee Information​

First, query Shield to get the current payment address and fee rates:

curl -XGET 'https://shield.rebarlabs.io/v1/info'

You'll receive a response like:

{
  "height": 886512,
  "payment": {
    "p2wpkh": "bc1q..."
  },
  "fees": [
    {
      "estimated_hashrate": 0.12,
      "feerate": 18.0
    },
    {
      "estimated_hashrate": 0.27,
      "feerate": 24.0
    }
  ]
}

2. Create a Transaction with Shield Fee​

When creating your Bitcoin transaction, add a Shield fee output:

  1. Choose a fee tier from the response above based on your confirmation needs. The estimated_hashrate represents an estimate of the cumulative % hashrate of the network's hashrate available at a given fee, and the corresponding fee rate (in sats/vbyte)
  2. Add an output paying the Shield fee address
  3. Calculate the fee: Transaction Size (vbytes) × Fee Rate (sats/vbyte)
  4. Set the Shield fee output to this amount (inputs must equal outputs — the implicit Bitcoin fee must be zero)

3. Submit the Transaction​

Submit your signed transaction to Shield:

curl -XPOST 'https://shield.rebarlabs.io/v1/rpc' \
  -H 'Content-Type: application/json' \
  -d '{
    "jsonrpc": "1.0",
    "id": "1",
    "method": "sendrawtransaction",
    "params": ["YOUR_SIGNED_TRANSACTION_HEX"]
  }'

On success, you'll receive the transaction ID:

{
    "result": "txid_hex_string",
    "error": null,
    "id": "1"
}

Code Examples​

JavaScript (Node.js with axios)​

const axios = require('axios');

async function submitTransaction(txHex) {
  try {
    // Get fee information
    const infoResponse = await axios.get('https://shield.rebarlabs.io/v1/info');
    console.log('Payment address:', infoResponse.data.payment.p2wpkh);
    console.log('Fee options:', infoResponse.data.fees);

    // Submit transaction
    const response = await axios.post('https://shield.rebarlabs.io/v1/rpc', {
      jsonrpc: '1.0',
      id: 'shield',
      method: 'sendrawtransaction',
      params: [txHex],
    });

    console.log('Transaction submitted:', response.data.result);
    return response.data.result;
  } catch (error) {
    console.error('Error:', error.response?.data || error.message);
    throw error;
  }
}

// Usage
// submitTransaction('YOUR_SIGNED_TRANSACTION_HEX');

Next Steps​