cPay — Confidential Payroll

cPay is a confidential onchain payroll app built with Zama FHEVM, ERC-7984, and standard browser wallets.

It supports a practical payroll workflow:

• ingest ISO 20022 pain.001
• execute confidential payroll onchain
• export pain.002 status receipts

Why cPay

• Payroll data should not be publicly readable onchain.
• cPay keeps salary amounts confidential while preserving settlement and audit trails.

Monorepo Structure

• apps/web — frontend (Vite + React)
• apps/api — backend API (faucet, decrypt, execute, health)
• packages/contracts — Solidity contracts and tests
• docs — public docs

Quick Start

npm install
npm --workspace apps/web run dev
npm --workspace apps/api run dev

Frontend runs on 5173 by default.
API runs on 8787 by default.

Build & Test

npm run contracts:compile
npm run contracts:test
npm --workspace apps/web run build

Contracts

npm run contracts:compile
npm run contracts:test

Core Capabilities

• Upload payroll instructions via ISO 20022 pain.001.
• Validate payroll batches before execution.
• Encrypt payroll amounts before onchain submission.
• Execute payroll through ERC-7984 confidential transfers.
• Download local payroll receipt as pain.002.
• Decrypt confidential balances from the connected account.

Runtime Modes (MVP)

• Execution: backend by default, wallet_direct for connected-wallet submission
• Decrypt: observer
• Faucet: backend

Configured via frontend env vars:

• VITE_EXECUTION_MODE
• VITE_DECRYPT_MODE
• VITE_FAUCET_MODE

Current MVP Constraints

• Operational batch limit: 15 payments/run (current stable range: 5/10/15).
• Contract-level hard cap remains MAX_BATCH_SIZE = 100.
• Decryption currently uses observer mode for stability.

Deployment

• Web target: Vercel
• API target: Fly.io
• Deployment runbook: docs/deployment.md

Public Documentation

• docs/overview.md
• docs/architecture.md
• docs/how-it-works.md
• docs/deployment.md
• docs/limitations.md
• docs/contributing.md

License

• Root project: ISC (see root package.json)
• Contracts package: MIT (packages/contracts/LICENSE)