These contracts provide the core functionality for the POA bridge. They implement the logic to relay assests between two EVM-based blockchain networks. The contracts collect bridge validator's signatures to approve and facilitate relay operations.

The POA bridge smart contracts are intended to work with the bridge process implemented on NodeJS. Please refer to the bridge process documentation to configure and deploy the bridge.

The POA Bridge allows users to transfer assets between two chains in the Ethereum ecosystem. It is composed of several elements which are located in different POA Network repositories:

Bridge Elements

1. Solidity smart contracts, contained in this repository.
2. Token Bridge. A NodeJS oracle responsible for listening to events and sending transactions to authorize asset transfers.
3. Bridge UI Application. A DApp interface to transfer tokens and coins between chains.
4. Bridge Monitor. A tool for checking balances and unprocessed events in bridged networks.
5. Bridge Deployment Playbooks. Manages configuration instructions for remote deployments.

Currently, the contracts support two types of relay operations:

• Tokenize the native coin in one blockchain network (Home) into an ERC20 token in another network (Foreign).
• Swap a token presented by an existing ERC20 contract in a Foreign network into an ERC20 token in the Home network, where one pair of bridge contracts corresponds to one pair of ERC20 tokens.

The POA bridge contracts consist of several components:

• The Home Bridge smart contract. This is currently deployed in POA.Network.
• The Foreign Bridge smart contract. This is deployed in the Ethereum Mainnet.
• Depending on the type of relay operations the following components are also used:
  • in NATIVE-TO-ERC mode: the ERC20 token (in fact, the ERC677 extension is used) is deployed on the Foreign network;
  • in ERC-TO-ERC mode: the ERC20 token (in fact, the ERC677 extension is used) is deployed on the Home network;
• The Validators smart contract is deployed in both the POA.Network and the Ethereum Mainnet.

Responsibilities and roles of the bridge:

• Administrator role (representation of a multisig contract):
  • add/remove validators
  • set daily limits on both bridges
  • set maximum per transaction limit on both bridges
  • set minimum per transaction limit on both bridges
  • upgrade contracts in case of vulnerability
  • set minimum required signatures from validators in order to relay a user's transaction
• Validator role:
  • provide 100% uptime to relay transactions
  • listen for UserRequestForSignature events on Home Bridge and sign an approval to relay assets on Foreign network
  • listen for CollectedSignatures events on Home Bridge. As soon as enough signatures are collected, transfer all collected signatures to the Foreign Bridge contract.
  • listen for UserRequestForAffirmation or Transfer (depending on the bridge mode) events on the Foreign Bridge and send approval to Home Bridge to relay assets from Foreign Network to Home
• User role:
  • sends assets to Bridge contracts:
    • in NATIVE-TO-ERC mode: send native coins to the Home Bridge to receive ERC20 tokens from the Foreign Bridge, send ERC20 tokens to the Foreign Bridge to unlock native coins from the Home Bridge;
    • in ERC-TO-ERC mode: transfer ERC20 tokens to the Foreign Bridge to mint ERC20 tokens on the Home Network, transfer ERC20 tokens to the Home Bridge to unlock ERC20 tokens on Foreign networks.

npm install

Please the README.md in the deploy folder for instructions and .env file configuration

npm test

npm run flatten

See the CONTRIBUTING document for contribution, testing and pull request protocol.

This project is licensed under the GNU General Public License v3.0. See the LICENSE file for details.