# Mezo Bridge Overview

_Overview of native asset flows between Bitcoin, Ethereum, and Mezo with design RFC references._

_Source: https://mezo.org/docs/developers/bridge/mezo-bridge_

Mezo Bridge enables native asset movement between Bitcoin, Ethereum, and Mezo. Below are the primary flows with references to the design RFCs.

### Bridge In to Mezo

From Bitcoin → Mezo

1. Lock BTC to the bridge-controlled address with metadata identifying the Mezo recipient.

2. Submit proof and attestation to Mezo Bridge contract.

3. Contract verifies proof.

4. Mint corresponding asset on Mezo to recipient.

From Ethereum → Mezo

1. Lock the ERC-20 on Ethereum via the Mezo Bridge contract, emitting an `AssetLocked` event with Mezo recipient.

2. Bridge validators listen for such events.

3. Bridge validators validate events inclusion and validator quorum.

4. Mint corresponding asset on Mezo to recipient.

### Bridge Out of Mezo

From Mezo → Bitcoin

1. Burn the asset on Mezo specifying the Bitcoin recipient address.

2. Submit proof and attestation to Mezo Bridge contract.

3. Contract verifies proof.

4. Upon verification, BTC is released to the recipient address.

From Mezo → Ethereum

1. Burn the asset on Mezo specifying the Ethereum recipient.

2. Bridge validators listen for `AssetsUnlocked` events.

3. Bridge validators validate events inclusion and validator quorum.

4. Upon verification, the ERC-20 is released to the recipient.

### Architecture

- **Lock/Burn on Source**: Assets are locked on Bitcoin/Ethereum (or burned on Mezo) with data that identifies the intended recipient and target chain.
- **Attestation & Relay**: Offchain clients produce attestations over source-chain events and relay proofs to the destination chain.
- **Mint/Release on Destination**: Upon valid attestation and proof verification, destination contracts mint wrapped assets or release locked funds.

### Core Flow

1. User initiates a bridge transfer specifying destination address and amount.

2. Source-chain contract/event is emitted after lock/burn; event includes unique sequence ID and parameters.

3. Offchain client collects confirmations/finality per RFC thresholds and submit proof+attestation to destination contract.

4. Destination verifies:
   - event authenticity
   - validator quorum/signatures

5. On success, destination executes mint/release and records completion.

### Enclave Deposits

Mezo Enclaves are an institutional feature that allows institutions with
regulatory custody requirements to still use their BTC on Mezo without
depositing into explicit bridges. Enclaves are given special capabilities
associated with legal agreements that describe bridge amounts and usage
limitations. All deposits into enclaves are still backed by UTXOs on the
Bitcoin chain, which are captured in the triparty bridge deposit transaction
and maintained in chain state. Enclaves are allowlisted by the Mezo governance
multisig individually. More on the underlying triparty bridge implementation
is available in [`mezod` RFC-6](https://github.com/mezo-org/mezod/blob/main/docs/rfc/rfc-6.md).

### Contracts

Mainnet:

- Mezo Bridge: [0xF6680EA3b480cA2b72D96ea13cCAF2cFd8e6908c](https://etherscan.io/address/0xF6680EA3b480cA2b72D96ea13cCAF2cFd8e6908c)
- Bridged tokens [list](https://mezo.org/docs/users/resources/contracts-reference#bridged-tokens)

Sepolia:

- Mezo Bridge: [0x3a3BaE133739f92a885070DbF3300d61B232497C](https://sepolia.etherscan.io/address/0x3a3BaE133739f92a885070DbF3300d61B232497C)
- Bridged tokens [list](https://mezo.org/docs/users/resources/contracts-reference#bridged-tokens)

### Audits

Please see the [Audits](https://github.com/mezo-org/audits) page for the latest audits.

## Additional Resources

For full technical details, message formats, and security rationale, see the following RFCs:

- [RFC-2: Bridging Bitcoin to Mezo](https://github.com/mezo-org/mezod/blob/main/docs/rfc/rfc-2.md)
- [RFC-4: Native non-Bitcoin asset Bridge](https://github.com/mezo-org/mezod/blob/main/docs/rfc/rfc-4.md)
- [RFC-5: Bridging assets out of Mezo](https://github.com/mezo-org/mezod/blob/main/docs/rfc/rfc-5.md)
- [RFC-6: Triparty BTC bridging](https://github.com/mezo-org/mezod/blob/main/docs/rfc/rfc-6.md)