Tamper-Resistant Dynamic Payment QR Display with Voice Confirmation for Small Shops
Printed payment QR stickers at small shops can be covered with a fraudster's sticker, and fake payment screenshots fool busy shopkeepers. Build a small counter device with a screen that shows a fresh, signed QR for each sale, and a speaker that announces confirmed payments only after the shop's own account receives them. Threat-model the attacks, build the device, and test it against sticker swaps and fake confirmations.
Intermediate
A small team, or one strong student willing to learn something new.1 to 2 semesters · 2 to 3 students
7 to ship
4 optional extrasSuggested stack
What you should ship
- A threat model of QR payment fraud at small shops: sticker swaps, fake screenshots, replayed confirmations, device theft
- A counter device that shows a dynamic QR per sale with amount and order reference
- A backend that issues signed payment requests and pushes confirmations to the device over an authenticated channel
- Voice announcement of the confirmed amount in a local language, only for verified confirmations
- Device provisioning with per-device keys and secure firmware updates
- An attack test plan with results: physical overlay, spoofed messages, replay and network loss
- A shopkeeper guide in plain language
If you have time left
- A tamper switch or light sensor that alerts if the screen is covered
- Offline mode that clearly shows "cannot confirm" instead of guessing
- Daily totals spoken at closing time
- A version that pairs with a cheap Android phone instead of custom hardware
The problem: the QR on the counter is not always yours
Small shops across South Asia now accept payments by QR. Most use a printed sticker that never changes. Fraudsters have pasted their own QR over a shop's sticker so customers pay the wrong account, and customers sometimes show fake "payment successful" screenshots. A busy shopkeeper serving several customers cannot check every payment in a banking app.
Pakistan's Raast P2M service, launched by the State Bank in 2023, supports dynamic QR codes that carry an amount and reference for each sale, which makes stronger protection possible if the shop has a device to show them.
What already exists and the gap
- Paytm Soundbox and PhonePe SmartSpeaker in India announce received payments aloud, which has become common at Indian shops.
- Bank and wallet merchant apps show notifications on the shopkeeper's phone.
- Printed static QR codes remain the norm for the smallest shops.
The gap is an open design that combines a per-sale QR with verified voice confirmation, built from a clear threat model and tested against the actual attacks.
Inspiration
India's soundbox devices show that audible confirmation changes shopkeeper behaviour, because they no longer need to look at a phone. Your project adds the security engineering: signed requests, authenticated confirmations and a documented attack test.
What you build
- Shopkeepers type an amount, the customer scans the QR on the device, and the device speaks the confirmed amount.
- Customers pay a QR that only exists for this sale, so a pasted sticker is useless.
- The provider manages devices, keys and firmware securely.
The technically interesting part
- Threat modelling first. List each attack, its cost to the attacker and your control. Some attacks, like a stolen device, need a process, not code.
- Authenticated confirmations. The device must only announce a payment that came from your backend over a mutually authenticated channel, with replay protection.
- Small device security. Per-device keys, secure boot or at least signed firmware updates, and no secrets in plain flash.
- Failure behaviour. When the network drops, the device should say it cannot confirm, never stay silent in a way that looks like success.
How to evaluate it
- Attack tests: document each attempted attack and whether it worked.
- Confirmation latency from simulated payment to voice announcement.
- Reliability: behaviour across Wi-Fi drops, power cuts and reboots.
- Shopkeeper test: whether people correctly tell confirmed from unconfirmed payments.
- Cost of the bill of materials.
Suggested plan
- Weeks 1 to 3: threat model and architecture.
- Weeks 4 to 8: device prototype, display and audio.
- Weeks 9 to 12: backend, provisioning and secure messaging.
- Weeks 13 to 16: firmware updates and attack testing.
- Weeks 17 to 20: shopkeeper test, report and demo.
Path to a product
Payment providers and banks rolling out merchant QR need affordable devices, and fraud losses give them a reason to pay. An open reference design with a published security evaluation could be licensed to a hardware maker or provider. The project shows embedded and security skills together, which is rare.
Scope warning
Use a simulated payment backend; do not connect to real payment systems or handle real money. Do not test attacks on real shops. Keep the hardware simple and focus on the security design.
Learn what you need on Sefism
- Embedded and IoT roadmap: ESP32, displays and audio.
- Cybersecurity roadmap: threat modelling and secure communication.
- ESP-IDF programming guide: secure boot, flash encryption and OTA updates.
- HiveMQ MQTT Essentials: messaging to devices.
- OWASP Cheat Sheet Series: key management and authentication.
Get help with this idea
Teams often build the gadget and skip the threat model. Tauseef can help you write the threat model first and plan attack tests you can actually run. If you are new here, create a free account first.
Ideas and guidance, not finished projects
These are project ideas and scoping guidance, published free for students to use as a starting point. I do not build, write, or sell final-year projects, and I do not complete coursework for anyone. Take an idea, make it yours, and build it.
Not sure this one fits you?
I help students pick an idea that matches their skills and their deadline, then scope it down until it is finishable. Guidance only, never done for you.
Stuck on something specific?
Writing only gets you so far. If you want an answer to your situation rather than the general case, book a session and we will work through it together. Sessions are free for approved Sefism members, and a few slots open each week.
Follow along
New writing, resources and project ideas land here first.