Buddy

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 authentication

Whether 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.

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 registration
• Solidity Smart Contracts: Handle HaLo chip registration, payment authorization, and secure transaction execution
• Crosschain Infrastructure (via Avail Nexus SDK): Enables unified USDC management across multiple chains with automatic routing

The smart contract suite includes:

• HaloPayment Contract: Manages HaLo chip registration, verifies cryptographic signatures from hardware devices, and executes secure USDC transfers with replay protection
• ENS Subname Registrar: Enables users to claim personalized .buddy.eth usernames for social identity within the ecosystem

The 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 chips
• Avail Nexus SDK: For crosschain USDC bridging, unified balance management, and transaction simulation
• DaisyUI + Tailwind CSS: For responsive mobile first UI optimized for payment flows Framer Motion: For smooth animations and intuitive payment status feedback

Buddy transforms physical NFC interactions into verified, onchain, secure, and instant payments.