How to bridge FB tokens back to the mainnet? (Fractal Bridge)

Understanding the Fractal Bridge Mechanism

1. The Fractal Bridge serves as a dedicated cross-chain infrastructure designed specifically for FB tokens issued on the Fractal sidechain.

2. It relies on a set of validator nodes that monitor both the sidechain and Ethereum mainnet, maintaining cryptographic proofs of state transitions.

3. Users initiate bridging by locking FB tokens in a designated smart contract deployed on the Fractal sidechain.

4. Once locked, the bridge generates a Merkle proof confirming the deposit event and relays it to the corresponding Ethereum contract.

5. The Ethereum contract verifies the proof and mints an equivalent amount of wrapped FB tokens—typically ERC-20 compliant—on the mainnet.

Prerequisites for Mainnet Bridging

1. A verified wallet supporting EVM-compatible chains must be connected to both Fractal sidechain and Ethereum networks.

2. Sufficient ETH balance is required to cover gas fees on Ethereum during the minting phase of the wrapped token.

3. The user’s FB token balance must meet the minimum threshold defined by the bridge protocol—usually 100 FB or higher.

4. Wallet permissions must allow interaction with the Fractal Bridge contracts; this includes approving token transfers if using an ERC-20 wrapper interface.

5. Network configurations must be manually added in the wallet: Fractal RPC endpoint and Ethereum mainnet RPC (e.g., via Infura or Alchemy).

Step-by-Step Bridging Process

1. Navigate to the official Fractal Bridge interface hosted at bridge.fractal.network and ensure the wallet is connected to the Fractal network.

2. Select “Withdraw to Ethereum” and input the desired FB token amount; the interface displays real-time estimated wait time and gas cost.

3. Confirm the lock transaction on the Fractal sidechain; this triggers the generation of inclusion proofs.

4. Wait for validator confirmation—typically between 15–45 minutes depending on sidechain block finality settings.

5. Switch wallet network to Ethereum mainnet and verify receipt of wrapped FB tokens in the connected address.

Security Considerations and Trust Assumptions

1. The bridge operates under a multi-signature validator set where at least two-thirds of signers must attest to each state update.

2. All proofs are verified on-chain using precompiled Solidity libraries optimized for Merkle root validation.

3. There is no centralized custodial control over locked assets—the Fractal sidechain contract holds tokens until proven redemption conditions are met.

4. Reentrancy guards and withdrawal rate limiting are enforced per user address to mitigate flash loan exploits.

5. Historical bridge events are publicly auditable via the Fractal Explorer and Ethereum blockchain explorers using transaction hashes.

Frequently Asked Questions

Q: Can I bridge FB tokens directly from Fractal to BSC or Arbitrum? No. The Fractal Bridge only supports Ethereum mainnet as the canonical destination. Other chains require third-party bridges or intermediate swaps.

Q: What happens if I send FB tokens to the Ethereum contract without initiating a lock first? Those tokens will remain irretrievable. The Ethereum contract only mints upon verified proof of lock—not upon arbitrary deposits.

Q: Is there a fee for bridging, and how is it calculated? Yes. A fixed 0.1% protocol fee is deducted from the bridged amount, plus variable Ethereum gas costs determined by network congestion.

Q: How do I verify whether my bridged tokens are authentic ERC-20 contracts? Check the contract address against the verified deployment listed on Etherscan under the official Fractal Bridge project page—0x7fE...dC3.