MPay

Project Name :

MPay

Project Description

NomadPay solves the "privacy trilemma" in blockchain payments by introducing the first practical MPC-based stealth address scanning system. Instead of forcing users to choose between privacy, decentralization, and usability, we achieve all three through distributed threshold cryptography.

The Core Innovation

Traditional stealth address implementations face a critical problem: how can mobile users privately discover their transactions without downloading the entire blockchain or trusting a centralized server?

Our breakthrough: Threshold ECDH on Elliptic Curves. We split the user's view private key using Shamir Secret Sharing, then perform distributed computation across multiple nodes to calculate the required v × R value without ever reconstructing the original private key.

Smart Contracts (Solidity + Foundry)

• SignalBoard.sol - Compressed point announcements
• StealthRegistry.sol - Full stealth protocol implementation
• PaymentProxy.sol - MPC-signed payment processing

MPC Network (Python + FastAPI)

• Shamir Secret Sharing for key distribution
• Coincurve for secp256k1 elliptic curve operations
• Lagrange interpolation for threshold reconstruction
• HTTP APIs for distributed node communication

Frontend (Next.js + WebCrypto)

• QR code generation and scanning
• Stealth address derivation (ECDH + keccak256)
• ECIES encryption for private memos
• MetaMask integration for wallet connectivity

GitHub Repository:https://github.com/goodyanki/ethtokyo2025