AccessFi

AccessFi lets event payments through NFC-enabled signing/payments. Users receive P-256 compatible SECP256k1 NFC cards linked to their wallets, enabling instant tap-to-pay for event tickets, registration, food, and merchandise while preserving privacy through deterministic encryption. And yesss, it works on any evm compatible chain.

Key Features: • Tap & Pay: Instant ticket purchasing and event payments via NFC • Privacy-First: Encrypted on-chain eligibility matching without exposing personal data • Universal Wallet: Single NFC card works across all events and venues • Magical Discovery: Users automatically see only events they're eligible to attend • Frictionless Registration: Organizers create events via tap-and-pay, users register instantly

The system eliminates payment friction, protects user privacy, and creates seamless event experiences for both organizers and attendees.

Critical Pain Points in Current Event Systems:

• Payment Friction: 3-5 minute transaction times cause massive queues; 45% abandon purchases

• Privacy Invasion: Excessive personal data collection with no user control

• Multi-Platform Complexity: Separate apps for tickets, payments, access, creating operational headaches

• Security Vulnerabilities: Cash theft, fake tickets, centralized system failures

• Poor Event Discovery: Manual searching through irrelevant events; missed opportunities

How AccessFi's Tap-and-Pay MVP Solves These Problems:

• Instant Payments Tap AccessFi NFC card = 5-second transactions. No apps, no PINs, no waiting. Works on any EVM chain (Ethereum, Polygon, BSC). Eliminates queues, increases vendor throughput 80%.

• Privacy-First Architecture Deterministic encryption matches users to events without exposing personal data. Organizers never see attendee information - only payment confirmations. Zero-knowledge proofs verify eligibility privately.

• Universal Wallet Single card replaces everything: tap-to-buy tickets, tap-to-register, tap-to-pay for food/drinks, tap-to-tip speakers, tap-for-access. One system handles all event payments.

• Hardware Security P-256 SECP256k1 chips provide tamper-resistant key storage. Cryptographic signing prevents counterfeiting. Short-range NFC (2-4cm) prevents remote attacks.

• Magical Discovery Encrypted algorithm shows users only relevant events they're eligible for. No manual searching. Organizers reach target audiences without invasive data collection.

MVP Demonstration: Physical NFC cards + NextJS browser website which works on mobile as nfc works on it, deployed on Polygon Amoy testnet, proving real hardware-blockchain integration for instant tap-and-pay event experiences.

AccessFi combines hardware NFC integration with blockchain smart contracts and privacy-preserving cryptography via creating zk proofs to verify the identity of the user via there signature (which was used at the login).

We found that the combination of wristbands and zk circuits are in such a high pressure hackathon deadline, meant that we had to think very carefully about what we could achieve. We had a rough idea of how it works, but we kept coming into interesting surprises when we were developing connection with the nfc band, be it how to sign a actual transaction and sending signed one to the chain broadcast or how to create a payload which would be signed via a tap and sign hardware.

Technical Architecture: • NFC Hardware: ARX.org P-256 compatible SECP256k1 chips for secure transactions • Smart Contracts: Solidity contracts handling payments, event creation, and eligibility verification • Frontend: Next js for browser application with NFC integration ( • Privacy Layer: Deterministic encryption for user-event matching without data exposure. Zk Proofs to prove the user's data in the browser. • Blockchain: Multi-chain support starting with Polygon Testnet for hackathon testing and transactions. We are going to accept in many evm compatible chains, because the use case of a hardware tap to pay wallet is infinite and the community is diverse. They can add tokens in any chain and pay to the organiser on any chain they want (still to be implemented yet). • Circom/MoPro (written in rust): MoPro is used to prove the circom circuit in the browser (taking under 2 seconds to prove in the browser). Circom was used to compile the circuits.

Notable Implementation: • Custom NFC-to-wallet integration enabling single-tap blockchain transactions • Zero-knowledge eligibility proofs allowing event registration without revealing personal data • Payment to participate in the eligible events in one tap • Hardware-software bridge connecting physical NFC cards to decentralized applications • Used ZK Compatible hash called poseidon 2 for cheap on chain and in circuit proofs.

The most challenging aspect was creating seamless NFC-blockchain integration while maintaining privacy guarantees through cryptographic protocols.