Token Bridge Architecture
The token bridge is one of the tools built by the bridge network which enables users to move assets from one supported chain to another. It is divided into two interdependent layers which includes:
- 1.Base / Protocol layer.
- 2.Control / Infrastructure layer.
Protocol layer: This layer comprises of the group smart contracts which is domicile on each network/chain supported by the bridge network, it acts as the base layer on which the bridges entire systems stems from. It's this smart contract that acts as vault for asset management, cross chain transactions and transaction validations. The smart contract includes:
- 1.Bridge / Vault contract
- 2.Controller contract
- 3.Settings contract
- 4.Deployer contract
- 5.Fee Controller/Management contract
- 6.Registry contract
Infrastructure layer: This layer is made up of two important components:
- 1.Oracles
- 2.Validators
The oracles are simple relayers that passes events from one chain to another. They listen for events on a source chain and relay that events on the destination chain. Usually there is a minimum confirmation required before the relayer sends the transaction to the destination chain, the confirmation number varies between chains.
The validators act as guardians of the protocol. Validators are added by governance to help secure the network by validating transactions. Once an oracle relays a transaction from the source to the destination chain, the validators pick the transaction and verify that the data passed by the oracle is the same as in the source chain. If the transaction is valid the validators sign the transaction with their private keys once the validation threshold is reached(by default can’t be less than 51%). The signatures are used to confirm the transaction which result in asset being minted or claimed depending on the type of transaction initiated.
Assets on Bridge Network are classified into two types:
- 1.Native assets
- 2.Foreign Assets
Native assets are those that originated on a specific chain. Example: ETH is a native asset on the ethereum blockchain. The ethereum blockchain is the source or native chain for ETH. Native assets are bridge through a lock and release mechanism. When a native asset is to be bridged to another blockchain, the native asset is locked on the source chain and a corresponding version of the asset is either unlocked or minted on the destination chain. Most native assets are wrapped on the destination chain by the
mint function, but in some cases, for assets like USDC where there reside a native version on the destination chain as well, the corresponding amount is unlocked from a pool of that native asset on the destination chain. To bridge back to the original or source chain, the wrapped version of the native asset on the destination chain can be sent back using the
burn function. Foreign Assets are wrapped version of a native asset. The assets exist on chains supported by the native assets. When a native asset is locked a corresponding foreign asset is minting on the destination chain on a 1:1 ratio. The foreign asset minting and burning is controlled by the bridge protocol and secured by the validators who guard the network ensuring the every asset minting has a corresponding native asset locked.
Bridging to another blockchain:
Bridging back to a native chain: