Selective Disclosure Demo

A demo application showing how Fully Homomorphic Encryption (FHE) enables privacy-preserving compliance on-chain. Users can mint confidential tokens, manage encryption permits, and selectively disclose balances to verifiers — without exposing their full wallet state.

Core narrative: "You don't have to choose between financial privacy and regulatory compliance. With FHE, you control exactly what you prove and to whom."

How It Works

The app has two roles, designed for a two-presenter live demo:

Token Holder (Wallet A)

1. Connect wallet to Arbitrum Sepolia
2. Encrypt an amount client-side and mint confidential cUSD tokens (ERC-7984)
3. Create a self-permit to decrypt and view their own balance
4. Generate an Access Control Permit (ACP) for a compliance verifier
5. Copy and share the ACP JSON off-chain

Compliance Verifier (Wallet B)

1. Connect a different wallet
2. Paste the ACP JSON received from the token holder
3. Click "Verify Balance" to decrypt and view the holder's balance
4. See a tamper-proof, cryptographically signed attestation — nothing else

Tech Stack

• Contracts: Solidity 0.8.25, ERC-7984 (confidential token standard), Fhenix CoFHE
• Client: React, Vite, TanStack Router, Zustand, Tailwind CSS v4, shadcn/ui
• Blockchain: Arbitrum Sepolia testnet
• FHE SDK: @cofhe/sdk for client-side encryption, permits, and decryption

Project Structure

selective-disclosure-demo/
  packages/
    hardhat/               # Smart contracts & deployment
      contracts/
        MockERC7984Token.sol   # Confidential ERC-7984 token
      deploy/
        00_deploy_MockERC7984Token.ts
    client/                # Frontend monorepo
      apps/web/            # Vite React app
      packages/
        ui/                # Shared UI components (shadcn)
        config/            # TypeScript config
        env/               # Environment validation

Prerequisites

• Node.js >= 20.18.3
• pnpm 9.x
• A browser wallet (MetaMask) configured for Arbitrum Sepolia

Setup

1. Install dependencies

pnpm install

2. Configure environment

cp packages/hardhat/.env.example packages/hardhat/.env

Edit packages/hardhat/.env and add your deployer private key:

DEPLOYER_PRIVATE_KEY=0x...

3. Compile contracts

pnpm compile

4. Deploy to Arbitrum Sepolia

pnpm deploy --network arbitrumSepolia

The deployed contract address will be saved in packages/hardhat/deployments/arbitrumSepolia/.

If you redeploy, update the address in packages/client/apps/web/src/contracts/MockERC7984Token.ts.

5. Start the client

pnpm start

The app runs at http://localhost:3001.

Deployed Contract

Contract	Network	Address
MockERC7984Token (cUSD)	Arbitrum Sepolia	0x442fa2307fE44B3F6C143B28321d40a95206E82f

Demo Script

Presenter A (Token Holder):

"I have USDC I want to keep private on-chain. I'm going to encrypt it — the amount is encrypted client-side before the transaction is even sent. Now, my compliance verifier needs to confirm I actually hold this position. Instead of exposing my entire wallet, I'm issuing a cryptographic permit — scoped specifically to this balance. I'll copy the permit and hand it to them."

Presenter B (Compliance Verifier):

"I've received a permit from the token holder. I'm going to paste it here and verify. What I get is a tamper-proof, cryptographically signed attestation of their encrypted balance — nothing else. Their full wallet state is still encrypted. This is what compliance-grade selective disclosure looks like."

Available Scripts

Command	Description
pnpm start	Start the client dev server
pnpm compile	Compile Solidity contracts
pnpm deploy	Deploy contracts
pnpm test	Run contract tests
pnpm client:build	Build the client for production
pnpm client:check-types	Type-check the client

License

MIT