Prove income.
Reveal nothing.

How it works

1. 01User connects to Plaid via OAuth. Income data stays in the browser.
2. 02A Circom Groth16 ZK circuit runs locally and answers: "Is my 6-month average income above the threshold?"
3. 03The proof (no names, no exact figures, no employer) is sent to the backend for verification.
4. 04User pays a small USDC attestation fee via x402.
5. 05A Soulbound SPL Token-2022 is minted on Solana, valid for 30 days, non-transferable.
6. 06Verifiers (a landlord, client, employer, or app) read the token and confirm you qualify.

Raw income data never leaves the client.

Architecture

Browser
  ├── OAuth (Plaid)                income data stays client-side
  └── Circom Groth16 (snarkjs)     ZK proof generated locally

Backend (Node.js + TypeScript, port 3001)
  ├── /auth      OAuth callback, session token
  ├── /income    Plaid income data (never forwarded to logs)
  ├── /proof     snarkjs Groth16 proof verification
  ├── /payment   x402 USDC attestation fee
  └── /solana    Anchor program interaction, token minting

Solana (devnet)
  ├── Anchor Program   verify Groth16 proof (BN254), mint/expire/revoke attestation
  └── SPL Token-2022   Soulbound (NonTransferable) attestation token

Income tiers

The circuit checks all 6 months have positive income and computes the floor average. The threshold is a private input. The verifier only sees the resulting tier.

Tech stack

Project structure

seel/
├── circuits/
│   └── income_proof_circom/   Circom circuit + trusted setup artifacts
├── programs/seel/             Anchor program (Rust)
├── backend/                   Node.js API
├── frontend/                  Next.js app
└── sdk/                       Verification SDK for integrators

Getting started

Prerequisites

• Node.js 18+
• Rust + Anchor CLI 0.30
• Solana CLI (devnet)
• circom + snarkJS (for circuit setup)

Backend

cd backend
cp .env.example .env   # fill in your credentials
npm install
npm run dev

Frontend

cd frontend
npm install
npm run dev

Anchor program

anchor build                              # production build
anchor build --features verify-skip       # local testing only, never deploy
anchor deploy --provider.cluster devnet

Never build for production with --features verify-skip.

Circom circuit

cd circuits/income_proof_circom
npm run setup   # compile, trusted setup, export verification key
# artifacts land in frontend/public/circuits/ automatically

Environment variables

Copy backend/.env.example to backend/.env and fill in:

Deployed addresses (devnet)

Privacy guarantees

• Income figures are private circuit inputs. They never leave the browser.
• The server receives a proof and public outputs only (tier: 1 or 2).
• API responses containing income data are never logged on the server.
• The on-chain token stores only tier, timestamps, and a proof hash.