StylusLink is a trustless payment protocol that transforms standard URLs into programmable Smart Drops.
StylusLink is a trustless, AI-gated payment protocol built on Arbitrum Stylus that transforms static URL links into programmable Smart Drops. It bridges the Hardware-Chain Gap by enabling users to claim digital assets using nothing but FaceID or TouchID, eliminating the need for seed phrases, private key management, or complex wallet interactions for recipients.
1. The Core Innovation: Solving the P-256 Cost Barrier
The single biggest technical barrier to mobile biometric adoption in Web3 has been gas costs. Mobile Secure Enclaves (Apple's Secure Enclave and Android Keystore) sign data using the secp256r1 (P-256) elliptic curve.
The Problem: Verifying a P-256 signature on the standard Ethereum Virtual Machine (EVM) is prohibitively expensive, costing between 300,000 and 1,000,000 gas due to the complex math required.
The StylusLink Solution: We leverage Arbitrum Stylus to write our Vault smart contract in Rust. This allows us to access the specific P-256 precompile at address 0x100 (enabled in ArbOS 51).
The Result: StylusLink verifies hardware-grade biometric signatures on-chain for approximately 7,000 gas—a 97% cost reduction compared to Solidity implementations. This makes biometric security economically viable for everyday micro-transactions.
2. Intelligent Smart Drops Powered by Gemini AI
Unlike traditional link drops which are just bearer instruments (whoever has the link gets the money), StylusLink integrates Google Gemini AI as a logic engine. This AI Gatekeeper acts as a decentralized oracle that interprets natural language rules set by the creator.
Instead of writing code, a creator can simply type: "Only allow users who have held a Pudgy Penguin NFT for more than 6 months and have a high on-chain reputation."
The AI Agent synthesizes data from multiple tools to make a boolean decision:
Financial History: Checks wallet age, lifetime gas spent, and transaction count via Etherscan.
Asset Verification: Validates ownership of specific ERC-20 tokens or NFTs across 5 mainnets, and their sepolia chains (Arbitrum, Optimism, Base, Polygon, Ethereum).
Social Proof: Verifies Discord guild membership and roles via the StylusLink Bot.
Sybil Resistance: Analyzes location (GPS) and wallet behavior to filter out bots.
3. Architecture & Security
StylusLink employs a Dual-Factor Security Model that requires two distinct cryptographic proofs to unlock the Vault:
Agent Signature (Logic Proof): The AI Gatekeeper validates that the user meets the off-chain criteria (e.g., "Is a member of the Discord") and signs a message using the Relayer's key.
Biometric Signature (Presence Proof): The user's device signs a challenge using the WebAuthn standard (Passkeys). This proves the physical presence of the user and binds the claim to their specific hardware.
The Vault Smart Contract (a stylus contract, written in Rust) holds the funds in escrow and only releases them when both signatures are verified valid on-chain. This means even if the AI server is compromised, an attacker cannot drain the vault without the physical biometric signatures of valid users.
4. Use Cases
Community Airdrops: "You can only claim 0.1 ETH, if you are a verified member of our Discord and have the OG role."
Location-Based Rewards: " You can only claim this reward, only if you are atmost 1km away from the Eiffel Tower."
Sybil-Resistant Onboarding: "Users get 0.01 ETH for gas, but only if their wallet score indicates they are a real human."
Knowledge Quests: "Answer this riddle correctly to unlock the prize." (The answer is hidden from the frontend and verified privately by the AI).
StylusLink is not just a payment app it is a protocol that modernizes how value is transferred. By combining Rust-based contracts, Arbitrum Stylus precompile optimizations, and Generative AI, we have built a system where money is programmable, secure, and accessible to anyone with a smartphone.
I entered this hackathon with a clear goal: To bridge the gap between hardware biometrics and on-chain payments, and I built the entire StylusLink protocol from scratch to make it happen. Starting with just the basic Stylus boilerplate, I spent the majority of my time engineering the Rust smart contract, specifically tackling the complex challenge of integrating the P-256 precompile. This was the biggest technical hurdle, as I had to manually implement the signature verification to ensure FaceID could be verified on-chain for a fraction of the usual gas cost. Once the vault was secure, I developed the Gatekeeper (backend), integrating Gemini AI to act as a logic oracle that interprets natural language rules. I wrapped everything in a custom Next.js frontend that handles the WebAuthn cryptographic handshakes. It was an intense sprint, but I successfully went from an empty repository to a fully functional, end-to-end verified payment protocol.
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