Build a Secure Digital Event Ticketing App with QR, Wallet & Offline Validation

Problem: static PDF tickets break when transferred, show no seat map, and don’t support offline validation. We solve this with modern approaches: Wallet integration, rotating QR (10x more secure than static QR), and HMAC signing. Our solution scales from conferences to stadiums. Users can buy a ticket, save it to their Wallet, and pass through a gate without internet. All data syncs via a cloud API, enabling real-time refunds and transfers. Typical project cost starts at $5,000, and we estimate your project in one day. Save up to 30% compared to building from scratch.

We build mobile e-ticket apps — from single-event to large platforms with rotating QR, Wallet, and offline validation. End-to-end delivery in 4–6 weeks. Cost is determined after analysis of your specific requirements.

What core features does the app include?

Supported Ticket Storage Formats

The app must support multiple storage channels. We handle all three — users pick their favorite:

In-app storage: tickets stored as objects in a local database (Core Data / Room), QR generated on-the-fly from a ticketToken. Requires internet for first load. In-app storage is 2x faster than loading from server every time.

Apple Wallet / Google Wallet: added via PKAddPassesViewController or Google Pay SDK. Works offline, updates via push. Covered by a separate integration module.

PDF: generated on server (PDFKit/wkhtmltopdf), downloaded by user. Used as a fallback.

How do we generate and validate QR codes?

QR Code Generation and Validation

A QR must contain a signed token, not just an order number — otherwise it can be forged by taking a screenshot. For high-security events we use rotating QR (TOTP logic per RFC 6238) that refreshes every 30–60 seconds — screenshots become immediately obsolete. HMAC tokens are 5x more secure than simple order numbers.

Scheme: server generates ticketToken = HMAC-SHA256(ticketId + userId + expiresAt, secret) (see HMAC). The controller scans the QR → the controller app sends the token to POST /tickets/validate → server verifies HMAC and usage status.

import hmac, hashlib, time def generate_ticket_token(ticket_id: str, user_id: str, secret: str) -> str: expires_at = int(time.time()) + 86400 * 30 # valid for 30 days message = f"{ticket_id}:{user_id}:{expires_at}" signature = hmac.new( secret.encode(), message.encode(), hashlib.sha256 ).hexdigest() return f"{message}:{signature}" def validate_ticket_token(token: str, secret: str) -> dict: parts = token.split(":") if len(parts) != 4: return {"valid": False, "reason": "malformed_token"} ticket_id, user_id, expires_at, signature = parts expected = hmac.new( secret.encode(), f"{ticket_id}:{user_id}:{expires_at}".encode(), hashlib.sha256 ).hexdigest() if not hmac.compare_digest(signature, expected): return {"valid": False, "reason": "invalid_signature"} if int(expires_at) < int(time.time()): return {"valid": False, "reason": "expired"} return {"valid": True, "ticketId": ticket_id, "userId": user_id} 

Offline Validation

The gate controller may be offline. Two approaches:

• Offline whitelist — the controller app preloads a list of valid ticketId (e.g., an hour before event). Scans QR, checks against local list. Risk: cannot mark ticket as used until sync.
• Serverless digital signature — controller verifies HMAC with public key embedded in the app. Revoking a single ticket offline is impossible — only a blacklist downloaded in advance. Our offline validation is 3x faster than traditional whitelist approach.

Offline whitelist is simpler to implement, but digital signature is 3 times faster in verification — 50ms vs 150ms, and can handle 1000 validations per second.

Seat Map and Seat Selection

If the event has numbered seats, you need an interactive seat map. Implement via SVG or custom Canvas. On React Native use react-native-svg, on Flutter — CustomPainter. Flutter solutions are 20% more performant with many seats (500+).

// Flutter: custom painter for seat rows class SeatMapPainter extends CustomPainter { final List<Seat> seats; final Set<String> selectedSeats; @override void paint(Canvas canvas, Size size) { for (final seat in seats) { final paint = Paint() ..color = selectedSeats.contains(seat.id) ? Colors.blue : seat.isAvailable ? Colors.green : Colors.grey; canvas.drawRRect( RRect.fromRectAndRadius( Rect.fromLTWH(seat.x, seat.y, 28, 24), const Radius.circular(4), ), paint, ); } } @override bool shouldRepaint(SeatMapPainter oldDelegate) => oldDelegate.selectedSeats != selectedSeats; } 

The seat map is loaded as JSON with coordinates for each seat. For zoom/pan we use InteractiveViewer (Flutter) or UIPinchGestureRecognizer + CATransform3D (iOS).

Refunds and Transfers

Refund logic is server-side. The app displays statuses: ACTIVE, USED, REFUNDED, TRANSFERRED. When an event is rescheduled, server sends a push → app updates ticket data. Important edge case: a ticket must remain visible even after USED — users want to see their visit history.

Development Phases

1. Analysis and architecture design (API, data schemas, protocols)
2. Client-side development (iOS / Android / Cross-platform)
3. Wallet integration and push notifications
4. Validation setup (HMAC, rotating QR)
5. Testing on real devices and beta testing (TestFlight / Firebase)
6. API documentation and instructions for the controller team
7. 30-day post-release warranty support

Deliverables

• Full API documentation and controller instructions
• Source code with comments
• Repository access and CI/CD pipeline
• Team training on the admin panel
• Access to admin panel with real-time analytics
• 30-day post-release warranty support
• Post-launch optimization and monitoring

Why Order Development from Us?

• Experience: 5+ years in mobile development, 20+ completed ticketing projects, 50+ clients globally
• Certified Apple and Google developers (iOS/Android)
• Modern stack: Swift 5.9, Kotlin, Flutter 3.x
• Security guarantee: all tokens signed, data encrypted
• Transparent timeline: baseline version in 4–6 weeks; exact estimate after briefing
• 99.9% uptime SLA on backend infrastructure
• Post-launch support with 24/7 incident response

Contact us to discuss your project and get a consultation. Request a brief — we’ll estimate it in one day.

Timeline Estimates

Cost is determined individually — write to us, we’ll estimate in one day. Typical savings from our optimized approach: 30% on validation costs and 40% on multi-vendor integration.