Architecture

The FBTC protocol's architecture is primarily structured around three main components: custodial addresses on the Bitcoin main chain, smart contracts on destination chains, and off-chain modules.

Custodial Addresses

Onchain Smart Contracts

Offchain Service

High-level Workflow

Mint Flow

Mint FBTC

1. Qualified users transfer native BTC to a pre-configured custodial address.

2. Qualified users interact with the Bridge contract and initiate a mint request.

3. The Bridge Monitor that monitors on-chain events in real-time detects the minting request.

4. Bridge Monitor also monitors BTC deposit transactions on the Bitcoin main chain.

5. Bridge Monitor sends the minting request to TSS Gateway.

6. TSS Gateway initiates a contract to confirm the minting of the Bridge contract. Multiple TSS Nodes co-sign through the MPC algorithm construct the transaction signature. Each TSS Node operates an independent risk control system that validates the deposit transactions and minting requests to secure the FBTC minting.

7. After the minting transaction is confirmed on the destination chain, the FBTC token is minted.

Burn Flow

Burn FBTC

1. A qualified user interacts with the Bridge contract and initiates a burn request.

2. The Bridge contract burns the qualified user's FBTC token.

3. The Bridge Monitor monitors the burn request event.

4. Bridge Monitor sends the withdrawal request to TSS Gateway.

5. TSS Gateway initiates a BTC transfer, and transfers the specified amount of BTC to the pre-configured withdrawal address of the qualified user. Multiple TSS Nodes co-sign through the MPC algorithm construct the transaction signature. Each TSS Node operates an independent risk control system that validates the BTC transfer transactions and burning requests to secure the FBTC unwrapping.

6. After the withdrawal transaction is confirmed on the Bitcoin main chain, TSS Gateway calls the Bridge contract to confirm that the withdrawal request has been processed.

Cross-chain Flow

FBTC Cross-chain Transfer

1. A user interacts with the bridge contract from the source chain and initiates a cross-chain request.

2. The Bridge contract burns the user’s FBTC.

3. Bridge Monitor monitors events on the source chain in real-time and detects the cross-chain request immediately.

4. Bridge Monitor sends the cross-chain request to TSS Gateway.

5. TSS Gateway initiates a contract call to the Bridge contract on the destination chain to confirm the FBTC cross-chain operation. Multiple TSS Nodes with individual risk control co-sign the confirmation transaction.

6. After the cross-chain transaction is confirmed on the destination chain, the specified number of FBTC tokens are minted for the users.