Buddy

Problem Statement

Buddy is a NFC powered payment platform that bridges the gap between physical and digital commerce through secure, tap to pay transactions. The platform combines HaLo / Arx chip technology with crosschain capabilities to create a seamless, contactless payment experience using USDC.The platform enables users to make instant payments by simply tapping their HaLo cards near a merchant's device. Users can register their HaLo cards as authorized payment methods, approve USDC spending, and execute secure transactions through cryptographic signatures generated directly on the hardware. Beyond simple payments, Buddy offers a comprehensive financial ecosystem with crosschain bridging capabilities powered by the Avail Nexus SDK. Users can seamlessly transfer USDC across multiple chains including Optimism, Polygon, Arbitrum, Base and Mainnet, with automatic routing and optimal fee management.The platform also features an integrated ENS subdomain system, allowing users to claim personalized usernames like alice.buddy.eth for easier identification and social connectivity within the ecosystem.Buddy uses: HaLo NFC chips for secure, hardware based payment authentication Smart contracts that manage payment authorization, registration, and execution Avail Nexus SDK for crosschain USDC transfers and unified balance management ENS subdomain registration for user friendly identity management Privy wallet integration for seamless web3 authenticationWhether you're a merchant looking to accept contactless crypto payments, a user wanting to bridge assets across chains, or someone seeking a modern web3 payment experience, Buddy makes digital transactions as simple as a tap, while maintaining the security and decentralization that blockchain technology provides.

Solution

We combined TypeScript, Solidity, and NFC hardware authentication to create a seamless tap to pay experience.The architecture is split into the following components:Next.js Frontend: React based interface for managing payments, cross chain transfers, and ENS username registrationSolidity Smart Contracts: Handle HaLo chip registration, payment authorization, and secure transaction executionCrosschain Infrastructure (via Avail Nexus SDK): Enables unified USDC management across multiple chains with automatic routingThe smart contract suite includes:HaloPayment Contract: Manages HaLo chip registration, verifies cryptographic signatures from hardware devices, and executes secure USDC transfers with replay protectionENS Subname Registrar: Enables users to claim personalized .buddy.eth usernames for social identity within the ecosystemThe frontend stack includes:Privy + Viem: For seamless wallet connectivity and Ethereum contract interaction@arx-research/libhalo: For NFC communication and cryptographic signature generation from HaLo chipsAvail Nexus SDK: For crosschain USDC bridging, unified balance management, and transaction simulationDaisyUI + Tailwind CSS: For responsive mobile first UI optimized for payment flows Framer Motion: For smooth animations and intuitive payment status feedbackBuddy transforms physical NFC interactions into verified, onchain, secure, and instant payments.