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Rootstock account abstraction

Note: The contracts and tests in this repo must be used with the appropriate version of RSKJ modified for account abstraction.

This project explores introducing account abstraction in Rootstock using the ERC-4337 design. An important part of this approach is the separation of a transaction's validation logic from its execution. The ERC is still a work in progress. However, some L2 rollup projects have implemented similar versions with "native" account abstraction. We start with code from a ZKSync tutorial from Matter Labs.

Our approach is to create a contract with "some: ERC-4337 features and then use RSKIP-167 (install code precompiled contract) to inject the compiled bytecode in the state trie under the node for an externally owned account (EOA). This will create a new type of EOA which can serve as a nearly native smart (contract) wallet.

Two key features of ERC4337 that we adopt are the separation of transaction validation and execution within the wallet. When processing a TX, a RSKJ node will call the wallet's ValidateTransaction method, and if it succeeds, then it will call the wallet's Execute method. To illustrate the generality of validation process the wallet is initiated with 2 owners, and for validation, a transaction must provide the concatenated ECDSA signature of each owner. This signature appears in a new EIP-2718 format new rransaction type. Noticeably absent from our appoach is any refence to ERC4337's paymaster (and associated contracts).

Motivation

Users on EVM chains are advised to store and manage their assets (coins, tokens, NFTs) using contracts, rather than EOAs. This approach results in a "smart (contract) wallet" which offers better security and UX. However, these smart wallets have two addresses: one of the user's EOA and another of the associated contract. One high-level goal of account abstraction is to combine both so that an account can have code as well.

Contracts

The contract TwoUserMultiSig.sol is an adaptation of one from a ZKSync tutorial. Some modification were simplifications to get rid of objects related to ZKSync's rollup system. We added some methods for batched validation and execution. Instead of zksync's libraries for singers, we extended ethers.js's TransactionRequest and UnsignedTransaction classes to encode transactions.

  • TwoUserMultiSig.sol: the main wallet
  • TransactionHelper.sol: simplified from the original and extended to separate encoding and hashing methods.
  • RLP.sol: a dependency
  • DummyDocMint.sol: this is a mintable ERC20 token. We use mint and transfer to create examples and tests wallet functionality including batching.

Running the PoC Wallet Tests

As noted at the top, since we use install code (RSK167) to inject bytecode into an EOA, this wallet can only be deployed and used with a version of RSKJ modified to include the installcode precompiled contract, introduce the new transaction type, as well as a host of changes reuired to validate and execute the new type of transactions.

Build the RSK client for AA-poc branch. Then start it in regtest mode

Once the RSKJ client is running:

npx hardhat test test/AA-test.ts # unit tests run on Hardhat network
npx hardhat test test test/AA-integration-test.ts --network localhost # this must be run with appropriate RSKJ node
npx hardhat test test test/AA-int-Batch-test.ts --network localhost #multicall AA