NexusFi

NexusFi is a mobile-first DeFi banking platform that brings Nubank-style financial services to the unbanked — without requiring a bank account, credit history, or KYC documents.
The problem: 1.4 billion adults worldwide are unbanked. Traditional banks require credit history, physical branches, and bureaucratic onboarding. Existing DeFi protocols are too complex for non-crypto-natives and lack real-world financial primitives like credit lines and fiat on-ramps.
NexusFi solves this by combining four Chainlink CRE workflows with Stellar/Soroban smart contracts and MoonPay fiat rails into a single, accessible platform:

1. nUSD Stablecoin with Proof of Reserve (CRE WF1): Users deposit fiat via PIX, SWIFT, Card, or SEPA through MoonPay. USDC arrives on Stellar, and CRE verifies reserves via the Stellar Horizon API every 30 seconds before minting nUSD 1:1. Every token is 100% backed and verifiable on-chain.
2. AI Credit Scoring (CRE WF2): CRE analyzes 50+ on-chain signals (transaction patterns, balance history, DeFi activity) using an LLM inside a Trusted Execution Environment. The result is a tamper-proof credit score — no bank, no credit bureau, no personal data exposed.
3. Risk Monitoring (CRE WF3): Automated circuit breakers watch reserve ratios, credit utilization, and price feeds. If thresholds are breached, minting pauses within seconds — protecting the protocol and its users without human intervention.
4. Confidential HTTP / Privacy Credit Check (CRE WF4): Sensitive API calls (banking APIs, KYC providers) are made through Chainlink's Confidential Compute. Credentials are encrypted client-side, decrypted only inside a TEE via threshold cryptography, and discarded after use. Only a boolean result (eligible: true/false) is published on-chain.
   Users interact through a passkey-based wallet (WebAuthn/FIDO2) — no seed phrases, no browser extensions. The entire platform runs as a PWA installable on any phone, making decentralized finance as simple as opening a banking app.

Frontend: Next.js 14 PWA (React 18, Tailwind CSS, Framer Motion) — mobile-first responsive design with passkey authentication via WebAuthn/FIDO2.
Backend: Node.js + Express + TypeScript API server handling Stellar interactions, MoonPay URL signing (server-side secrets), CRE workflow bridge, and webhook verification.
Smart Contracts: Three Soroban (Rust) contracts on Stellar Testnet:

• nexusfi_token — nUSD stablecoin (SEP-41 compliant)
• credit_score — On-chain AI credit score storage
• credit_line — Decentralized credit line logic (borrow, repay, manage)
  Chainlink CRE Workflows: Four workflows in TypeScript compiled to WASM (workflows/cre/main.ts):
• WF1: Proof of Reserve — fetches Stellar Horizon API to verify USDC reserves, attests on Ethereum Sepolia
• WF2: AI Credit Scoring — aggregates on-chain signals, calls LLM via Confidential HTTP, computes score inside TEE
• WF3: Risk Monitor — checks reserve ratios, utilization, and price feeds; triggers safeguards when thresholds are breached
• WF4: Privacy Credit Check — uses Confidential HTTP to call external credit/KYC APIs without exposing credentials on-chain
  Fiat On/Off-Ramp: MoonPay integration supporting PIX (Brazil), SWIFT (global), Card (global), and SEPA (Europe). Backend generates signed widget URLs; MOONPAY_SECRET_KEY stays server-side only.
  Infrastructure: Monorepo deployed on Railway (frontend + backend). Stellar Testnet for smart contracts. Ethereum Sepolia for CRE attestations.
  Architecture flow: Mobile PWA → Express Backend → Stellar/Soroban (nUSD, credit contracts) + Chainlink CRE (4 workflows) + MoonPay (fiat rails) → Ethereum Sepolia (cross-chain attestations)