Specifications

Introduction

Interchain account is system that allows other chain to manage the accounts on another chain via Inter-Blockchain Communication (IBC).
Interchain accounts are managed by another chain while retaining all the capabilities of a normal account. While an Ethereum CA's contract logic is performed within Ethereum's EVM, Interchain accounts are managed by another chain via IBC in a trustless way.

Implementation

This repo is on proof-of-concept level yet. And, IBC on Ethereum is not implemented yet. Currently, this implements only the interface needed to implement an interchain account.

InterchainAccount Contract

InterchainAccount is ownable contract. And, owner will be the InterchainAccountRouter that creates this InterchainAccount contract.
Owner can request a tx by runTx method in InterchainAccount contract. runTx will execute transaction to to address with requested value (ether) and data. data can be made by ABI specification.

function runTx(address to, uint256 value, bytes memory data) public onlyOwner returns (bool, bytes memory) {
    return to.call(data);
}

InterchainAccountRouter Contract

InterchainAccountRouter is responsible to generate the interchain account and deserialize the interchain account tx and execute it.

If RegisterIBCAccountPacket is delivered from IBC, createAccount will create new interchain account and returns its address to sending chain. RegisterIBCAccountPacket includes the salt to help the receiving chain to create an address and sending chain can calculate the address to be generated in advance.
But, currently, solidity supports CREATE2 as only assembly code. So generating new address with salt deterministically is not easy. This feature will be implemented in near future.

function createAccount() public returns (address) {
    InterchainAccount iaContract = new InterchainAccount();
    interchainAccounts[address(iaContract)] = true;
    emit InterchainAccountCreated(address(iaContract));
    return address(iaContract);
}

receiveRunTxPacket method in InterchainAccountRouter contract is mockup method for mocking the process in receiving RunTxPacket.
This will deserialize the tx bytes by ABI and check authentication and execute tx.

function receiveRunTxPacket(bytes memory txBytes) public {
    InterchainAccountTx memory interchainAccountTx = deserializeTx(txBytes);
    authenticateTx(interchainAccountTx);
    require(runTx(interchainAccountTx));
}

struct InterchainAccountTx {
    address from;
    address to;
    uint256 value;
    bytes data;
}

deserializeTx will deserialize tx bytes by ABI.
You can make tx bytes by encoding [from, to, value, data] by ABI in order.

function deserializeTx(bytes memory txBytes) private returns (InterchainAccountTx memory) {
    address from;
    address to;
    uint256 value;
    bytes memory data;
    (from, to, value, data) = abi.decode(txBytes, (address, address, uint256, bytes));
    InterchainAccountTx memory interchainAccountTx;
    interchainAccountTx.from = from;
    interchainAccountTx.to = to;
    interchainAccountTx.value = value;
    interchainAccountTx.data = data;
    emit InterchainAccountDeserialzed(from, to, value, data);
    return interchainAccountTx;
}