mate-qr-payments

MATE QR Payments is a gasless retail payment solution built on EVVM's MATE Metaprotocol that eliminates gas fees for customers through the Fisher pattern. Merchants generate payment QR codes, customers scan and sign transactions using EIP-191 signatures, and our Fisher contract executes payments on-chain without requiring customers to hold ETH for gas.

The system addresses crypto adoption's biggest barrier: transaction fees. In retail scenarios, customers shouldn't worry about gas costs when making small purchases. Our solution enables true gasless payments where the Fisher contract pays gas fees on behalf of users, making crypto payments as simple as scanning a QR code.

The application features a merchant dashboard for generating payment QR codes and a customer interface with camera-based QR scanning or image upload. All transactions are secured through cryptographic signatures and executed on EVVM's virtual blockchain infrastructure on Sepolia testnet, demonstrating how abstract blockchains can enable novel payment patterns impossible on traditional blockchain architectures.

The project uses Foundry for smart contract development with a custom Fisher contract deployed on Sepolia that implements the gasless execution pattern. The Fisher contract inherits from EVVM's architecture and includes replay attack prevention through nonce tracking and EIP-191 signature validation.

The frontend is built with Next.js 15 and React 19, using ethers.js v6 for Web3 interactions. We implemented QR code generation using the qrcode library and scanning functionality with qr-scanner, supporting both camera capture and image upload for maximum accessibility. The UI is styled with TailwindCSS for a modern, mobile-first design.

The gasless payment flow works by having customers sign payment intent messages off-chain using EIP-191 signatures. These signed messages are submitted to our Fisher contract which validates the signature, checks the nonce to prevent replay attacks, and executes the payment on the MATE EVVM contract. The Fisher pays all gas fees, enabling truly gasless transactions for end users.

Integration with EVVM MATE Metaprotocol was key as it provides the virtual blockchain infrastructure that makes gasless patterns feasible. We leveraged EVVM's async nonce system and executor pattern for optimal performance. The architecture demonstrates how EVVM's infra-less blockchain concept enables novel use cases like retail payments that would be impractical with traditional blockchain gas fees.

Notable technical decisions include using the Fisher contract as a wrapper around EVVM calls rather than direct integration, allowing for better error handling and future extensibility. We also implemented automatic network switching to Sepolia and comprehensive error states for production-ready UX.