Token Transfers

Sending ERC20 Tokens to Polkadot

The bridge currently supports sending ERC20 tokens from Ethereum to any Polkadot parachain, and back again.

The bridged tokens are minted in ForeignAssets pallet of the AssetHub parachain, and then transferred to the final destination using a reserve transfer.

A token transfer can be initiated with a single transaction to our Gateway contract.

How to send tokens to a parachain

Sending tokens is usually a single step for the user. However, a preliminary registration step is required for tokens which have not previously been bridged before.

Token Registration

First, the ERC20 token needs to be registered on AssetHub in the ForeignAssets pallet.

This can initiated by sending the following transaction to the Gateway.

/// @dev Send a message to the AssetHub parachain to register a new fungible asset
///      in the `ForeignAssets` pallet.
function registerToken(address token) external payable;

This function will charge a fee in Ether that can be retrieved ahead of time by calling quoteRegisterTokenFee.

Token Sending

To send a previously registered token to a destination parachain, send this transaction to the Gateway:

/// @dev Send ERC20 tokens to parachain `destinationChain` and deposit into account `destinationAddress`
function sendToken(address token, ParaID destinationChain, MultiAddress destinationAddress, uint128 destinationFee, uint128 amount)
    external
    payable;

This function will charge a fee in Ether that can be retrieved ahead of time by calling quoteSendTokenFee.