LP-0068Finalprivacyteleportbridgecross-chainshielded

LP-068: Cross-Chain Private Transfers

Abstract

Defines a protocol for private cross-chain transfers on Lux Network. A user deposits into a shielded pool (LP-064) on the source chain and withdraws from a corresponding pool on the destination chain. The cross-chain message is relayed via Warp messaging (LP-6022) and contains only the commitment proof and nullifier -- no amounts, senders, or receivers are revealed in the cross-chain message.

Specification

Protocol Flow


Source Chain                          Destination Chain
1. User deposits into ShieldedPool
2. Pool emits commitment event
3. Warp message: {root, nullifier,    ---->  4. DestPool verifies Warp signature
   proof, destChain, recipient_hash}         5. DestPool verifies ZK proof
                                             6. DestPool releases funds to recipient

Warp Message Format

| Field | Type | Description |

|-------|------|-------------|

| sourceChainID | bytes32 | Origin chain identifier |

| sourcePool | address | ShieldedPool address on source chain |

| merkleRoot | bytes32 | Commitment tree root at proof time |

| nullifierHash | bytes32 | Nullifier preventing double-spend |

| proof | bytes | ZK proof of valid deposit on source chain |

| recipientHash | bytes32 | Poseidon2 hash of recipient address (not plaintext) |

Liquidity

Each chain maintains a ShieldedPool funded by liquidity providers. LPs deposit into destination pools and earn fees from private transfer volume. Pool balances are public (aggregate liquidity) but individual deposit/withdrawal links are hidden.

Cross-Chain Nullifier Sync

Nullifiers must be globally unique across all chains. The protocol maintains a nullifier registry per chain and includes the source chain ID in the nullifier derivation:


nullifier = Poseidon2(commitment || spending_key || sourceChainID)

Warp-relayed nullifiers are checked on the destination chain before releasing funds.

Security Considerations

1. The Warp message reveals the source and destination chains but not the sender, receiver, or amount.

2. Recipient hash prevents front-running -- only the intended recipient can claim.

3. Liquidity pool size determines the anonymity set on the destination chain.

4. Cross-chain replay is prevented by including the source chain ID in the nullifier.

Reference

| Resource | Location |

|----------|----------|

| PrivateTeleport contract | github.com/luxfi/standard/contracts/privacy/PrivateTeleport.sol |

| Warp messaging | github.com/luxfi/evm/warp/ |

| ShieldedPool | github.com/luxfi/standard/contracts/privacy/ShieldedPool.sol |

Copyright

Licensed under the MIT License.