Ethereum Privacy Round Trip POC

Mainnet-only proof of concept for an Ethereum-facing privacy round trip:

ETH / USDC / WBTC on Ethereum
  -> optional Uniswap V3 swap to USDC
  -> Circle CCTP V2 to a browser-generated Starknet account
  -> Starknet privacy pool
  -> user-selected minimum delay
  -> private withdrawal into a CCTP exit anonymizer
  -> Circle CCTP V2 to a per-flow Ethereum settlement contract deployed at exit time
  -> optional USDC swap to ETH / WBTC
  -> recipient chosen before the first transaction, disclosed to the relayer only after the delay

This repository is a POC, not audited production software. Mainnet assets have real value. The web app fails closed until every deployment address and required upstream is configured.

Interaction budget

• ETH input: one Rabby transaction prompt.
• USDC or WBTC input: one ERC-20 approval prompt when needed, then one entry transaction prompt.
• No wallet prompt occurs after the entry transaction.

The browser generates the Stark account key and pool secret in memory. Closing or reloading the tab while a transfer is active destroys those secrets and can make the funds unrecoverable. This tradeoff is specific to the one/two-prompt POC. A production version needs recoverable key derivation or a separately reviewed scoped delegation design.

Workspace

Path	Responsibility
apps/web	Rabby connection, route form, ephemeral secrets, transaction submission, privacy flow and status UI
apps/api	Mainnet quotes, Circle access, Starkscan proof jobs, allow-listed provider proxying, public flow state
packages/shared	Mainnet constants, wire types, validation and lifecycle state machine
contracts/evm	Entry router and immutable per-flow exit settlement contract
contracts/starknet	Pool-only CCTP exit anonymizer
docs/ARCHITECTURE.md	Trust boundaries, sequencing, failure handling and deployment gates

Local development

Requirements: Node.js 24+, npm, Foundry, Scarb 2.17+.

npm install
cp apps/api/.env.example apps/api/.env
cp apps/web/.env.example apps/web/.env.local
npm run dev

The default configuration is mainnet-only but intentionally has no deployed POC contract addresses. The UI remains read-only until those addresses are supplied.

Verification

npm run check
forge test --root contracts/evm
scarb build --manifest-path contracts/starknet/Scarb.toml

Do not deploy or run a real-funds flow until the checklist in docs/ARCHITECTURE.md is complete.