privacy-bridge

A value-movement engine for the starknet-privacy privacy pool. It moves USDC between everyday EVM wallets/chains and the privacy pool, so users can fund a private balance and later withdraw it — without linking the two sides on-chain.

What it does

• Into the pool — takes USDC from an EVM wallet and deposits it into the privacy pool as a private note.
• Out of the pool (BUY leg) — withdraws from the pool and bridges USDC to a destination EVM chain, driven by the OutboundAnonymizer Cairo contract.
• Back into the pool (RETURN leg) — bridges USDC from an EVM chain back into the pool via the inbound InboundAnonymizer Cairo contract, which binds the incoming funds to a private note.
• Cash out — withdraws from the pool to the user's own EVM wallet.

Cross-chain USDC transfers use Circle's CCTP (burn-and-mint with attestation). All client-side key material — Starknet key, viewing key, per-account EVM keys, and the note commitments — is derived from a single wallet signature.

Privacy model

The bridge is designed so that the deposit side and the withdrawal side of a transfer cannot be linked on-chain. Secrets (the wallet signature and derived private keys) are never logged, persisted, or revealed on-chain — the on-chain claim recomputes everything from the authenticated signer. The only capability that may be persisted is the read-only viewing key (it can discover notes but cannot move funds).

Components

• packages/bridge-anonymizers — the OutboundAnonymizer and InboundAnonymizer Cairo contracts (Scarb workspace member). Build: scarb build · Test: scarb test.
• packages/bridge-core — the framework-agnostic TypeScript engine: value-movement orchestrators, key derivation, CCTP integration, and optional React hooks.
• apps/bridge — a demo web app built on bridge-core.

See CLAUDE.md for the full architecture.