API Security Best Practices for POS Systems

Security is paramount when handling payment and customer data. Follow these best practices to build secure POS applications with the NoPOS API.

Authentication & Authorization

Use API Keys Securely

Never expose API keys in client-side code:

// ❌ BAD: API key in frontend code
const response = await fetch('https://api.nopos.dev/v1/products', {
  headers: {
    'Authorization': 'Bearer sk_live_YOUR_SECRET_KEY'  // DON'T DO THIS
  }

// ✅ GOOD: API key on backend only // Make requests from your server `

Implement Proper RBAC

Use role-based access control to limit permissions:

const roles = {
  cashier: ['read:products', 'create:transactions'],
  manager: ['read:products', 'create:transactions', 'read:reports'],
  admin: ['*']
};

Data Protection

Encrypt Sensitive Data

Always use HTTPS and encrypt sensitive data at rest:

// All NoPOS API endpoints use TLS 1.3
const config = {
  baseURL: 'https://api.nopos.dev',  // Always HTTPS
  // Additional encryption for sensitive fields
  encryptFields: ['card_number', 'cvv', 'ssn']
};

Tokenize Payment Information

Never store raw payment card data:

// Use payment tokenization

// Send token to NoPOS, not raw card data const payment = await nopos.processPayment({ payment_token: token.id, // Tokenized, not raw card data amount: 100.00 }); `

Input Validation

Validate All Inputs

Never trust client input:

function validateTransaction(data) {
  // Validate required fields
  if (!data.amount || data.amount <= 0) {
    throw new Error('Invalid amount');
  }
  
  // Sanitize inputs
  const sanitized = {
    amount: parseFloat(data.amount),
    customer_id: sanitizeString(data.customer_id),
    items: data.items.map(validateItem)
  };
  
  return sanitized;
}

Prevent SQL Injection

Use parameterized queries:

// ❌ BAD: String concatenation

// ✅ GOOD: Parameterized query const query = 'SELECT * FROM orders WHERE id = ?'; db.query(query, [orderId]); `

Rate Limiting

Implement Rate Limiting

Protect your API from abuse:

const limiter = rateLimit({ windowMs: 15 * 60 * 1000, // 15 minutes max: 100, // Limit each IP to 100 requests per window message: 'Too many requests, please try again later' });

app.use('/api/', limiter); `

Logging & Monitoring

Log Security Events

Monitor for suspicious activity:

// Log authentication attempts
logger.info('Login attempt', {
  user_id: userId,
  ip_address: req.ip,
  timestamp: new Date(),
  success: true

// Alert on suspicious patterns if (failedAttempts > 5) { alertSecurity('Multiple failed login attempts', { userId, ip }); } `

Audit Trails

Maintain comprehensive audit logs:

const auditLog = {
  user_id: userId,
  action: 'refund_transaction',
  transaction_id: transactionId,
  amount: refundAmount,
  timestamp: new Date(),
  ip_address: req.ip

await saveAuditLog(auditLog); `

Webhook Security

Verify Webhook Signatures

Always verify webhook authenticity:

function verifyWebhook(payload, signature, secret) { const hmac = crypto.createHmac('sha256', secret); const digest = hmac.update(payload).digest('hex'); return crypto.timingSafeEqual( Buffer.from(signature), Buffer.from(digest) ); } `

Compliance

PCI DSS Compliance

When handling payment data:

Never store CVV codes
Tokenize card numbers
Use PCI-compliant payment processors
Encrypt data in transit and at rest
Conduct regular security audits

GDPR Compliance

Protect customer privacy:

Obtain consent for data collection
Provide data export capabilities
Implement right to deletion
Document data processing activities

Security Checklist

[ ] API keys secured on backend only
[ ] HTTPS enforced on all endpoints
[ ] Input validation implemented
[ ] Rate limiting configured
[ ] Payment data tokenized
[ ] Webhook signatures verified
[ ] Security logging enabled
[ ] Regular security audits scheduled
[ ] Compliance requirements met
[ ] Incident response plan documented

Additional Resources

[PCI Security Standards](https://www.pcisecuritystandards.org/)
[OWASP API Security](https://owasp.org/www-project-api-security/)
[NoPOS Security Documentation](https://developer.nopos.dev/security)

Stay secure and check our Developer Portal for the latest security guidelines.