📱 NFC Payments in MyZubster: A Complete Guide
How tap‑to‑pay with Monero works, from the gateway to the mobile app.
📌 Introduction
Near‑Field Communication (NFC) is the technology behind contactless payments. In MyZubster, NFC enables tap‑to‑pay with Monero – a customer simply taps their phone against a terminal or an NFC tag, and the payment request is automatically prepared.
This guide explains:
What NFC payments are and how they work with Monero
The Monero URI standard and why it matters
How MyZubster implements NFC payments end‑to‑end
How to integrate NFC into your own app
Security considerations and best practices
🧠 What Are NFC Payments?
NFC (Near‑Field Communication) allows two devices to exchange data when they're within a few centimeters of each other. In the context of payments, NFC enables a contactless experience: instead of scanning a QR code or typing a long address, the customer simply taps their phone.
How NFC Works with Cryptocurrency
NFC does not transfer cryptocurrency directly. Instead, it transmits a payment request – typically a URI (Uniform Resource Identifier) that contains:
The recipient's address
The amount to pay
An optional description or order ID
The customer's wallet reads this URI and prepares the transaction. The customer then confirms the payment on their device, and the transaction is broadcast to the network.
This means NFC doesn't replace the blockchain – it just makes the user experience faster and more convenient.
📋 The Monero URI Standard
Monero uses a specific URI format for payment requests. This format is defined in the official Monero documentation and is supported by most Monero wallets (Cake Wallet, Monerujo, etc.).
URI Format
text
monero:
?tx_amount=&tx_description=Parameters
Parameter Description Example
address The recipient's Monero address (or subaddress) 4A...
tx_amount The amount in XMR (decimal) 7.5
tx_description Optional description (URL‑encoded) Order%20123
Example
text
monero:4A...?tx_amount=7.5&tx_description=Order%20123
Why This Matters
The URI format is standardized, which means:
Any Monero wallet can read it
No custom parsing is required
The wallet handles the transaction preparation automatically
MyZubster uses this exact format when writing payment data to NFC tags.
🏗️ MyZubster NFC Payment Architecture
MyZubster's NFC payment flow involves three components:
text
┌─────────────────────────────────────────────────────────────────────────────┐
│ NFC Payment Flow │
├─────────────────────────────────────────────────────────────────────────────┤
│ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ 1. ORDER CREATION (Gateway) │ │
│ │ – Seller creates an order via web or mobile │ │
│ │ – Gateway generates a unique Monero subaddress │ │
│ │ – Order is stored in the database │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ │ │
│ ▼ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ 2. PAYMENT REQUEST (Mobile App) │ │
│ │ – App fetches the subaddress and amount from the gateway │ │
│ │ – App builds the Monero URI: │ │
│ │ monero:<subaddress>?tx_amount=<amount>&tx_description=Order │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ │ │
│ ▼ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ 3. NFC WRITING (Mobile App) │ │
│ │ – App writes the URI to an NFC tag (or emulates a tag) │ │
│ │ – The tag is now ready for the customer to tap │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ │ │
│ ▼ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ 4. CUSTOMER TAP (Customer's Wallet) │ │
│ │ – Customer taps their phone against the tag │ │
│ │ – Their Monero wallet reads the URI │ │
│ │ – Wallet prepares the transaction │ │
│ │ – Customer confirms the payment │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ │ │
│ ▼ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ 5. CONFIRMATION (PaymentMonitor) │ │
│ │ – The PaymentMonitor (on the gateway) detects the transaction │ │
│ │ – After 10+ confirmations, the order is automatically completed │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
└─────────────────────────────────────────────────────────────────────────────┘
Key Components
Component Role
MyZubster Gateway Generates subaddresses, stores orders, monitors payments
Mobile App (React Native) Builds the URI, writes to NFC tags, communicates with the gateway
Customer's Wallet Reads the NFC tag, prepares and confirms the transaction
NFC Tag Physical storage for the payment request (or emulated via HCE)
PaymentMonitor Watches the blockchain and completes orders automatically
📱 Implementing NFC in React Native / Expo
The mobile app uses react-native-nfc-manager to handle NFC operations. Here's how to set it up.
- Install Dependencies bash
cd ~/myzubster-mobile
npx expo install react-native-nfc-manager
- Configure app.json (Expo Config Plugin)
Add the plugin to your app.json or app.config.js:
json
{
"expo": {
"plugins": [
[
"react-native-nfc-manager",
{
"nfcPermission": "This app needs NFC access to read and write payment tags",
"includeNdefEntitlement": true
}
]
]
}
}
- Create the NFC Service javascript
// src/services/nfcService.js
import NfcManager from 'react-native-nfc-manager';
// Build the Monero URI
export const buildMoneroUri = (address, amount, orderId) => {
return monero:${address}?tx_amount=${amount}&tx_description=Order%20${orderId};
};
// Write payment to an NFC tag
export const writePaymentToNfc = async (address, amount, orderId) => {
await NfcManager.start();
const uri = buildMoneroUri(address, amount, orderId);
const bytes = NfcManager.bytesFromString(uri, 'ascii');
const record = NfcManager.ndef.createUriRecord(bytes);
const message = NfcManager.ndef.encodeMessage([record]);
await NfcManager.transceive(message);
await NfcManager.stop();
};
- Important: Use a Development Build
Expo Go does not support NFC. To test NFC, you need to create a development build:
bash
npx expo run:android # for Android
npx expo run:ios # for iOS (requires Mac)
🛡️ Security Considerations
Subaddresses for Privacy
Each order gets a unique Monero subaddress. This ensures:
Privacy – payments cannot be linked to the seller's main wallet
Traceability – each payment is tied to a specific order
Security – no address reuse, reducing the risk of tracking
No Private Keys on the Tag
The NFC tag contains only a payment request (address + amount), not any private keys. The customer's wallet holds the private keys and signs the transaction. This means:
The tag cannot be used to steal funds
Even if the tag is compromised, no funds are at risk
The customer retains full control over their wallet
PaymentMonitor for Reliability
The PaymentMonitor runs on the gateway and checks the blockchain every 30 seconds. This ensures that even if the customer's wallet doesn't send a confirmation, the order will still be completed automatically.
🧪 Testing NFC Payments
-
Prerequisites
A physical NFC tag (NTAG215 or compatible)
A device with NFC hardware (Android or iPhone 7+)
A Monero wallet that supports NFC (Cake Wallet, Monerujo)
A development build of the app (not Expo Go)
-
Test Flow
Create an order via the web or mobile app
Generate a subaddress using the gateway
Write the payment request to an NFC tag
Tap the tag with a phone that has a Monero wallet
Confirm the payment on the wallet
Wait for the PaymentMonitor to complete the order
Debugging
Check the app logs:
bash
npx expo start --tunnel
And the gateway logs:
bash
journalctl -u myzubster-gateway -n 30 --no-pager | grep -i "payment"
🚀 Future Enhancements
Feature Description
Host Card Emulation (HCE) Emulate an NFC tag directly from the phone (no physical tag needed)
iOS NFC Support Full support for reading NFC tags on iOS (currently limited)
Tap‑to‑Pay Terminals Integration with physical POS terminals using NFC
Multiple Wallets Support for other wallets that read NFC URIs
📚 Related Documentation
Monero URI Format: docs.getmonero.org
React Native NFC Manager: github.com/revtel/react-native-nfc-manager
MyZubster Mobile README: MyZubsterGateway/mobile/README.md
🙌 Final Thoughts
NFC payments make Monero as easy to use as a contactless credit card. No QR codes, no typing addresses – just tap and pay. By combining the Monero URI standard, subaddress generation, and the PaymentMonitor, MyZubster delivers a seamless, private, and secure payment experience.
If you're building a decentralized marketplace or a crypto payment app, NFC is a powerful addition. The code is open‑source and ready to use.
Tap to pay. Privacy by default. 🚀
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