Integration Guide

This guide explains how to integrate MiraclePay into your application to accept cryptocurrency payments. The External Payments API (base path /external/v1) lets you create payment requests programmatically and redirect customers to a hosted checkout page. All requests are signed with your API key — see Authentication.

Contents:

• Prerequisites
  • API Keys
  • Supported Blockchains
  • Get Active Blockchains
  • Base URL
  • Rate Limits
• Authentication
  • Request Headers
  • The Canonical String
  • Worked Example
  • Code Samples
  • Common Failure Modes
  • Key Rotation
• External Payments API
  • The Payment Object
  • Create a Payment Prompt
  • US Merchant Accounts
  • Idempotency
  • Retrieve a Payment
  • List Payments
  • Get Active Blockchains
  • Errors
  • End-to-End Example
  • Best Practices
  • Allowed Redirect Domains
• Redirect to Checkout
  • Checkout URL Structure
  • Redirect Methods
  • Checkout Flow
  • Post-Payment Handling
  • Payment Expiration
• Checking Payment Status
  • Webhooks vs Polling
  • Payment Status Values
  • Polling for Status
  • Polling Implementation
  • Background Job Pattern
  • Status Transition Diagram
  • Best Practices
• Webhooks
  • Setup
  • Event Types
  • Event Envelope
  • Delivery Headers
  • Verifying Signatures
  • Delivery and Retries
  • Best Practices

Quick Start

1. Create an API key in the merchant panel under Settings → Developer → API Keys — you get a key ID (mpay_pk_...), a secret (mpay_sk_..., shown only once) and a passphrase

2. Sign your requests with HMAC-SHA512 — see Authentication

3. Create a payment prompt via POST /external/v1/payments/prompt — amounts are in cents (1099 = $10.99). Standard accounts pass blockchainIds; US merchant accounts omit it — see External Payments API

4. Redirect your customer to the returned checkoutUrl

5. Confirm the outcome via Webhooks or GET /external/v1/payments/:id — never from redirect query parameters

import { createHmac, randomUUID } from "node:crypto";

const BASE_URL = "https://api.miraclecash.info";

async function createPayment() {
  const method = "POST";
  const path = "/external/v1/payments/prompt";
  const rawBody = JSON.stringify({
    amount: 1099, // $10.99 in cents
    blockchainIds: ["eth-usdc"],
  });

  const timestamp = Math.floor(Date.now() / 1000).toString();
  const nonce = randomUUID();
  const signature = createHmac("sha512", process.env.MPAY_SECRET!)
    .update([timestamp, nonce, method, path, rawBody].join("\n"))
    .digest("hex");

  const response = await fetch(`${BASE_URL}${path}`, {
    method,
    headers: {
      "Content-Type": "application/json",
      "X-MP-KEY-ID": process.env.MPAY_KEY_ID!,
      "X-MP-PASSPHRASE": process.env.MPAY_PASSPHRASE!,
      "X-MP-TIMESTAMP": timestamp,
      "X-MP-NONCE": nonce,
      "X-MP-SIGNATURE": signature,
    },
    body: rawBody,
  });

  const { prompt, checkoutUrl } = await response.json();
  // Redirect your customer to checkoutUrl
}