This document will walk you through how to use Hyperlane to enable fast native transfers to and from your L2 via a custom gas token.

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Primary Motives

  1. Create a custom gas token to use on your L2 of choice.
  2. Use this gas token to enable fast native transfers, instead of long wait times for settlement via canonical bridges.

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Pre-Requisites

To complete the following walkthrough, you should have the following available:
  1. A L2 network (”yourchain”) on which you are able to specify a custom gas token and would like to enable fast native transfers to and from.
  2. A sole deployer or authorized owner to receive mint of the receipt token (more information on this token below).
  3. An installed instance of the Hyperlane CLI and a wallet private key sourced as HYP_KEY, funded on all relevant networks.

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Walkthrough: Fast Native Transfers

  • Note that a “receipt token” below is a (one-time) mintable “dummy” token used to collateralize a warp-route on yourchain’s corresponding L1. You will burn the minting rights to the token after creating it. - Also, depending on your L2, the token symbol of your custom gas token may be assigned the same symbol as your receipt token. If deploying on ethereum, you may want to set your symbol to ETH.

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1. Deploy a Receipt Token

Deploy an ETH receipt token to ethereum to become your L2’s custom gas token.
  1. For example, you may deploy your receipt token via Remix with a funded wallet and a contract similar to below: 
    // SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

contract YourchainETH is ERC20 {
    constructor() ERC20("YourchainETH", "ETH") {
        _mint(msg.sender, 10000000 * (10 ** 18));
    }
}
  2. Ensure 100% of the total supply of your ETH receipt token is minted to the deployer or authorized address of choice. This must be a one-time mint event in order to avoid value dilution of the ethereum ↔ yourchain native HWR, below.
  3. Once deployed, save the address of the contract for use below.

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2. Set the Custom Gas Token

Set the custom gas token on yourchain to the newly deployed ETH ERC20 receipt token.
  1. To set a custom gas token using OP stack: https://docs.optimism.io/builders/chain-operators/features/custom-gas-token
  2. To set a custom gas token using arbitrum orbit: https://docs.arbitrum.io/launch-orbit-chain/how-tos/use-a-custom-gas-token

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3. Transfer All Receipt Tokens

Use your L2’s canonical bridge to transfer 100% of the ETH receipt token from ethereum to yourchain.
  1. To transfer using the OP stack standard bridge: https://docs.optimism.io/builders/app-developers/bridging/standard-bridge
  2. To transfer using the arbitrum orbit bridge: https://docs.arbitrum.io/launch-orbit-chain/how-tos/add-orbit-chain-to-bridge-ui

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4. Deploy a Native Hyperlane Warp Route (HWR)

Using the Hyperlane CLI, deploy an ethereum ETH EvmHypNative ↔ yourchain ETH EvmHypNative HWR:
  1. Run hyperlane warp init and complete the following flow:
    1. Select ethereum and yourchain using space, and hit enter.
    2. For ethereum, select native and accept the mailbox.
    3. For yourchain, select native and accept the mailbox.
  2. Before executing the deployment, ensure yourchain’s metadata.yaml has a blockExplorers field defined. This will be needed for contract verification in order to easily collateralize yourchain’s HWR.
  3. Run hyperlane warp deploy and confirm the warp deploy config is as expected.
  4. After execution, your yourchain-ethereum-config.yaml deployment file will look similar to the following: 
    # yaml-language-server: $schema=../schema.json
tokens:
  - addressOrDenom: "0x3e5bB1a03fef5DB15A320885E6A0C8Bff8b656bd"
    chainName: yourchain
    connections:
      - token: ethereum|ethereum|0x6d64832bDB4F04721D4F23CCbF17326cb636101e
    decimals: 18
    name: Ether
    standard: EvmHypNative
    symbol: ETH
  - addressOrDenom: "0x6d64832bDB4F04721D4F23CCbF17326cb636101e"
    chainName: ethereum
    connections:
      - token: ethereum|yourchain|0x3e5bB1a03fef5DB15A320885E6A0C8Bff8b656bd
    decimals: 18
    name: Ether
    standard: EvmHypNative
    symbol: ETH

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5. Collateralize Your HWR

Deposit yourchain ETH as collateral into yourchain’s native HWR via the receive() function. If needed, you may use the verified contract to do this via your scanner’s UI, or a wallet such as Metamask This collateralizes the native HWR, enabling users to bridge their native assets quickly to and from yourchain.

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6. Testing

You can initiate a test transfer of a single wei with the following command: 
hyperlane warp send --relay --symbol ETH
The --relay flag is optional and will relay the message to the destination chain. You can also run a relayer that delivers only for your HWR in the background with: 
hyperlane relayer --symbol TOKEN
You can test in either direction between where you have the HWR set.
By Default, your warp core config is found in the local Registry at $HOME/.hyperlane/deployments/warp_routes to be used with the --warp flag.
🎉 Congrats! You have now enabled fast native transfer to and from yourchain via a custom gas token on your L2.
Please note that this collateralization strategy takes on certain ISM trust assumptions.

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Resources

Take a look at the inEVM bridge to see an example of these HWRs in action. Check out some additional information, published by the Hyperlane supporting team & Injective: