Leechael / substrate-evm_account_mapping

EVM Account Mapping Pallet for Substrate

This is a Substrate pallet that enable interactive with EVM-compatible wallets.

It give us a chance to lure EVM chains Web3ers to try the amazing Polkadot economic or Sub-based standalone chains.

Highlights:

• Account mapping, not abstraction
  • the Substrate account is 1:1 mapping from ETH private key
  • User can export the private key and import to Polkadot.js extension to take full control of the Substrate account
• Super lightweight, super easy to integrate to Substrate chains
  • The pallet only dependent pallet-transaction-payment
  • No extra RPC or RuntimeAPI
  • No need to modify the Runtime or node
• Super lightweight, super easy to integrate to frontends
  • No forked package
  • No monkey patch, no injection

Try

Import ETH private key to Polkadot.js

This is optional, only do it if you want to take full control of the wallet.

• You can get wallet's private key from "Account detail" on MetaMask
• In Polkadot.js app, click "+ Account"
  • Select "Raw seed", paste the private key to seed (hex or string)
    • You need to add 0x for prefix
  • Expand "Advanced creation options" and select "ECDSA (Non BTC/ETH compatible)"
  • Check "I have saved ..." and click "Next"
• You can import the saved Json to the polkadot.js extension
  • There is no way to create an ECDSA wallet directly

Here's a seed private key for test: 0x415ac5b1b9c3742f85f2536b1eb60a03bf64a590ea896b087182f9c92f41ea12

Run the dev node

$ cargo build --release
$ target/release/node-template --dev

Run the demo frontend

See demo/README.md

Integrate

Integrate to your Substrate-based blockchain

First, add the pallet to your runtime Cargo.toml

Then, add config to your runtime

parameter_types! {
	pub EIP712Name: Vec<u8> = b"Substrate".to_vec();
	pub EIP712Version: Vec<u8> = b"1".to_vec();
	pub EIP712ChainID: pallet_evm_account_mapping::EIP712ChainID = sp_core::U256::from(0);
	pub EIP712VerifyingContractAddress: pallet_evm_account_mapping::EIP712VerifyingContractAddress = sp_core::H160::from([0u8; 20]);
}

impl pallet_evm_account_mapping::Config for Runtime {
	type RuntimeEvent = RuntimeEvent;
	type RuntimeCall = RuntimeCall;
	type Currency = Balances;
	type ServiceFee = ConstU128<10000000000>;
	type OnUnbalancedForServiceFee = DealWithServiceFee;
	type CallFilter = frame_support::traits::Everything;
	type EIP712Name = EIP712Name;
	type EIP712Version = EIP712Version;
	type EIP712ChainID = EIP712ChainID;
	type EIP712VerifyingContractAddress = EIP712VerifyingContractAddress;
	type WeightInfo = pallet_evm_account_mapping::weights::SubstrateWeight<Runtime>;
}

Integrate to your dApp

See frontend-sdk/README.md

Technical details

TD;LR:

• EVM-compatible chains private keys are ECDSA which Substrate supports it as well
• The difference is how calculate address
  • We can get the public address, and calculate ETH address and Substrate address which 1:1 mapping
• To confirm the user's identity, we can ask the wallet sign the Substrate call
  • The pallet will verify it
  • We choose EIP-712 standard signature for better visibility and security
• Because the call signed by a ETH wallet, we have to make it be an unsigned call
  • That's why meta_call
• For security, we simulate the signed call workflow (SignedExtra)
  • frame_system::CheckNonZeroSender<Runtime>
  • frame_system::CheckSpecVersion<Runtime>
  • frame_system::CheckTxVersion<Runtime>
  • frame_system::CheckGenesis<Runtime>
  • frame_system::CheckEra<Runtime>
  • frame_system::CheckNonce<Runtime>
  • frame_system::CheckWeight<Runtime>
  • pallet_transaction_payment::ChargeTransactionPayment<Runtime>

Understand how to make meta call data

You can check the PoC code to understanding theory.

deno run --allow-all docs/poc.ts

Here's a sample to send a call for system.remarkWithEvent("Hello")

evmAccountMapping.metaCall("5DT96geTS2iLpkH8fAhYAAphNpxddKCV36s5ShVFavf1xQiF", system.remarkWithEvent("Hello"), 0, "0x37cb6ff8e296d7e476ee13a6cfababe788217519d428fcc723b482dc97cb4d1359a8d1c020fe3cebc1d06a67e61b1f0e296739cecacc640b0ba48e8a7555472e1b", None)

Before try this, transfer some token to 5DT96geTS2iLpkH8fAhYAAphNpxddKCV36s5ShVFavf1xQiF

License

This project released under Apache License, Version 2.0.