# Bridging Architecture

LBTC and BTC.b are natively available across multiple blockchains. This page explains how cross-chain transfers work and the security mechanisms protecting them.

***

### How Bridging Works

When you bridge LBTC from one chain to another, tokens aren't literally "moved." Instead:

1. LBTC is burned on the source chain
2. The burn is verified by multiple parties
3. LBTC is minted on the destination chain

The total supply across all chains remains constant. Bridging just changes where your tokens exist.

***

### Dual Verification

What makes Lombard's bridging different is dual verification. Every cross-chain transfer requires approval from two independent systems:

**1. Bridge validators:** The bridge infrastructure (Chainlink CCIP or LayerZero) verifies the burn on the source chain

**2. Security Consortium:** Lombard's Consortium independently verifies and authorizes the mint

Both must approve. If either system rejects the transfer, it doesn't go through.

#### Why This Matters

Most bridge hacks exploit a single point of failure. Compromise the bridge and steal the funds. With dual verification:

* A compromised bridge alone can't mint unbacked tokens
* A compromised Consortium alone can't bypass bridge security
* An attacker needs to compromise both systems simultaneously

This significantly raises the difficulty of a successful attack.

***

### Bridge Infrastructure

Lombard uses established bridge protocols rather than building proprietary infrastructure.

#### Chainlink CCIP

Chainlink Cross-Chain Interoperability Protocol (CCIP) is the primary bridge for major EVM chains.

**How it works:**

* Chainlink's decentralized oracle network validates cross-chain messages
* Risk Management Network provides additional verification
* Configurable finality requirements per chain

**Chains using CCIP:**

* Ethereum ↔ Base
* Ethereum ↔ BNB Smart Chain

→ [CCIP documentation](https://chain.link/ccip)

#### LayerZero

LayerZero extends coverage to additional chains through its Omnichain Fungible Token (OFT) standard.

**How it works:**

* Decentralized Verifier Networks (DVNs) validate messages
* OFT Adapters handle cross-chain token transfers
* Configurable security parameters

**Chains using LayerZero:**

* Berachain
* Corn
* Etherlink
* Sonic
* Solana
* Swell
* TAC

→ [LayerZero documentation](https://layerzero.network/)

#### IBC (Inter-Blockchain Communication)

IBC connects Lombard to the Cosmos ecosystem.

**How it works:**

* Native Cosmos interoperability standard
* Light client verification
* Burn and mint style bridging via IBC v2

**Chains using IBC:**

* Cosmos Hub
* Babylon Genesis

→ [IBC documentation](https://ibcprotocol.org/)

#### Native Consortium Bridging

Some chains have direct Consortium and Bascule deployments without relying on third-party bridge infrastructure.

**Chains with native Consortium support:**

* Ethereum
* Base
* BNB Smart Chain
* Katana
* Monad
* Stable
* Starknet
* Sui

***

### Supported Chains

LBTC is currently available on:

| Chain           | Bridge Method     |
| --------------- | ----------------- |
| Ethereum        | Native            |
| Base            | CCIP              |
| BNB Smart Chain | CCIP              |
| Berachain       | LayerZero         |
| Corn            | LayerZero         |
| Etherlink       | LayerZero         |
| Katana          | Native Consortium |
| Monad           | Native Consortium |
| Sonic           | LayerZero         |
| Solana          | LayerZero         |
| Stable          | Native Consortium |
| Starknet        | Native Consortium |
| Sui             | Native Consortium |
| Swell           | LayerZero         |
| TAC             | LayerZero         |
| Babylon         | IBC               |

BTC.b is available on:

| Chain  | Bridge Method     |
| ------ | ----------------- |
| Monad  | Native Consortium |
| Stable | Native Consortium |
| Katana | Native Consortium |

***

### Bridge Transfer Flow

Here's the complete flow when you bridge LBTC:

#### Step 1: Initiate Transfer

You select source chain, destination chain, and amount in the Lombard app. The app prepares a bridge transaction.

#### Step 2: Burn on Source

Your LBTC is burned on the source chain. This transaction is confirmed according to the chain's finality requirements.

#### Step 3: Bridge Verification

The bridge protocol (CCIP or LayerZero) detects the burn and validates the message. Validators confirm the transaction is legitimate.

#### Step 4: Consortium Verification

The Security Consortium independently verifies the burn event. Members check that the amount and destination match.

#### Step 5: Authorization

Both the bridge and Consortium provide signatures authorizing the mint on the destination chain.

#### Step 6: Mint on Destination

LBTC mints to your address on the destination chain. You receive the same amount you burned (minus any bridge fees).

#### Timing

Transfer time depends on source and destination chain finality requirements. LayerZero transfers are typically faster than CCIP transfers. IBC transfers to Cosmos chains may take longer due to relayer processing.

***

### Fees

Bridge transfers incur fees from multiple sources:

**Gas fees:** You pay gas on the source chain to initiate the transfer

**Bridge fees:** CCIP/LayerZero charge fees for cross-chain messaging

**Destination gas:** Covered by bridge fees or paid separately depending on configuration

Lombard does not charge additional protocol fees for bridging.

***

### Security Considerations

#### Finality

Bridges wait for source chain finality before processing. This prevents issues with chain reorganizations.

#### Rate Limiting

Unusual bridge patterns (like sudden large transfers) may trigger additional verification or delays.

#### Emergency Pause

Bridge operations can be paused if security issues are detected, protecting funds from ongoing exploits.

#### Monitoring

Hexagate provides real-time monitoring of bridge activity, alerting to anomalous patterns.

***

### Next Steps

* [**Bridge LBTC**](https://docs.lombard.finance/use/bridging) — Step-by-step bridging guide
* [**Smart Contracts**](https://docs.lombard.finance/learn/transparency/smart-contracts) — Bridge contract addresses
* [**Security Model**](https://docs.lombard.finance/learn/lombard-security-model) — How dual verification protects your funds


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