Expanding the EVM tooling ecosystem.

Arbiter is a framework for stateful Ethereum smart-contract simulation. The framework features an ethers-rs middleware built on top of revm which allows the end user to interact with a sandboxed revm instance as if it were an Ethereum node. This provides a familiar interface for interacting with the Ethereum Virtual Machine (EVM), but with unrivaled speed. Furthermore, Arbiter provides containment and management for simulations. For a running list of vulnerabilities found with Arbiter, please see the Vulnerability Corpus.

Overview

The Arbiter workspace has three crates:

• arbiter: The binary crate that exposes a command line interface for initializing simulations via a templated repository and generating contract bindings needed for the simulation.
• arbiter-core: The lib crate that contains the core logic for the Arbiter framework including the RevmMiddleware discussed before, the Environment which envelopes simulations, and the Manager who controls a collection of environments.
• arbiter-derive: The lib crate that contains custom derive macros for more succinct simulation building.

The purpose of Arbiter is to provide a toolset to construct arbitrary agents (defined in Rust, by smart contracts, or even other foreign function interfaces) and have these agents interact with an Ethereum-like environment of your design. All contract bytecode is run directly using a blazing-fast EVM instance revm (which is used in live RPC nodes such as reth) so that your contracts are tested in the exact same type of environment that they are deployed in.

Motivation

Smart contract engineers need to test their contracts against a wide array of potentially adversarial environments and contract parameters. The static stateless testing of contracts can only take you so far. To truly test the security of a contract, you need to test it against a wide array of dynamic environments that encompass the externalities of Ethereum mainnet. We wanted to do just that with Arbiter.

Both smart contract and financial engineers come together in Decentralized Finance (DeFi) to build and deploy a wide array of complex decentralized applications as well as financial strategies respectively. For the latter, a financial engineer may want to test their strategies against thousands of market conditions, contract settings, shocks, and autonomous or random or even AI agents all while making sure their strategy isn't vulnerable to bytecode-level exploits.

To configure such a rich simulation environment on a test or local network is also possible with Arbiter by a change in choice of middleware. The most efficient choice for getting robust, yet quick, simulations would bypass any networking and use a low level language's implementation of the EVM. Furthermore, we can gain control over the EVM worldstate by working directly on revm. We would like the user to have a choice in how they want to simulate their contracts and Arbiter provides that choice.

Sim Driven Development and Strategization

Test driven development is a popular engineering practice to write tests first, which fail, and implement logic to get the test to eventually pass. With simulation driven development, it's possible to build "tests" that can only pass if the incentives actually work. For example, a sim driven test might be is_loan_liquidated, and a simulation must be made for a liquidator agent to do the liquidation. This approach significantly improves the testing of economic systems and other mechanism designs, which is important in the world of networks that are mostly incentive driven.

The same goes with developing strategies that one would like to deploy on a live Ethereum network. One can use Arbiter to simulate their strategy with an intended goal and see if it actually works. This is especially important in the world of DeFi where strategies are often a mix of on and offchain and are susceptible to exploits.

Installation

To install Arbiter, you will need to have Rust installed on your machine. You can install Rust by following the instructions here. Once you have Rust installed, you can install Arbiter by running the following commands:

cargo install arbiter

This will install the Arbiter binary on your machine. You can then run arbiter --help to see that Arbiter was installed properly as well as see the help menu.

Command Line Interface

The Arbiter binary provides a CLI for creating new project much like Foundry, which Arbiter aims to work alongside with. It also gives you the abilities to fork a state of an EVM network and store it to disk so that you can use this fork in a simulation.

Initialization

To create a new project, you should have Foundry installed. You can find the installation here. To create a new Arbiter project, you can run:

arbiter init your-project-name
cd your-project-name

This initializes a new Arbiter project with a template. You can generate the bindings again by running:

arbiter bind

The template is executable at this point and you can run it by running:

cargo run

Optional Arguments

You can run arbiter init <simulation_name> --no-git to remove the .git directory from the template upon initialization.

Bindings

You can load or write your own smart contracts in the templates contracts/ directory and begin writing your own simulations. Arbiter treats Rust smart-contract bindings as first-class citizens. The contract bindings are generated via Foundry's forge command. arbiter bind wraps forge with some convenience features that will generate all your bindings to src/bindings as a rust module. Foundry power-users are welcome to use forge directly.

Forking

To fork a state of an EVM network, you must first create a fork config file. An example is provided in the example_fork directory. Essentially, you provide your storage location for the data, the network you want the block number you want, and metadata about the contracts you want to fork.

arbiter fork <fork_config.toml>

This will create a fork of the network you specified in the config file and store it in the location you specified. It can then be loaded into an arbiter-core Environment by using the Fork::from_disk() method.

Forking is done this way to make sure that all emulation done does not require a constant connection to an RPC-endpoint.

Optional Arguments You can run arbiter fork <fork_config.toml> --overwrite to overwrite the fork if it already exists.

Optional Arguments

You can run arbiter init <simulation_name> --no-git to remove the .git directory from the template upon initialization.

Documentation

To see the documentation for the Arbiter crates, please visit the following:

• arbiter
• arbiter-core
• arbiter-derive

You will also find each of these on crates.io.

Benchmarks

In arbiter-core, we have a a small benchmarking suite that compares the RevmMiddleware implementation over the Environment to the Anvil local testnet chain implementation. The biggest reasons why we chose to build Arbiter was to gain more control over the EVM environment and to have a more robust simulation framework, but we also wanted to gain in speed which is why we chose to build our own interface over revm as opposed to using Anvil (which does use revm under the hood). For the following, Anvil was set to mine blocks for each transaction as opposed to setting an enforced block time and the Environment was set with a block rate of 10.0 (this was chosen somewhat arbitrarily as we will add in more block control in the future). Preliminary benchmarks of the RevmMiddleware interface over revm against Anvil are given in the following table.

to run the benchmarking code yourself, you can run:

cargo bench --package arbiter-core -F contracts

bench from 10/24/23 arbiter-core v0.6.3

Operation	RevmMiddleware	Anvil	Relative Difference
Deploy	238.975µs	7712.436µs	~32.2729x
Lookup	565.617µs	17880.124µs	~31.6117x
Stateless Call	1402.524µs	10397.55µs	~7.413456x
Stateful Call	2043.88µs	154553.225µs	~75.61756x

bench from 06/??/23ish arbiter-core v0.4.??

Operation	RevmMiddleware	Anvil	Relative Difference
Deploy	241.819µs	8.215446ms	~33.97x
Lookup	480.319µs	13.052063ms	~27.17x
Stateless Call	4.03235ms	10.238771ms	~2.53x
Stateful Call	843.296µs	153.102478ms	~181.55x

The above can be described by:

• Deploy: Deploying a contract to the EVM. We deployed both ArbiterToken and ArbiterMath in this method, so you can divide the time by two to get an estimate for the time it takes to deploy a single contract.

• Lookup: Looking up a the balanceOf for a client's address for ArbiterToken. We called ArbiterToken's balanceOf function 100 times in this method. Divide by 100 to get the time it takes to lookup a single balance.

• Stateless Call: Calling a contract that does not mutate state. We called ArbiterMath's cdf function 100 times in this method. Divide by 100 to get the time it takes to call a single stateless function.

• Stateful Call: Calling a contract that mutates state. We called ArbiterToken's mint function 100 times in this call. Divide by 100 to get the time it takes to call a single stateful function.

The benchmarking code can be found in the arbiter-core/benches/ directory and these specific times were achieved over a 1000 run average. The above was achieved running cargo bench --package arbiter-core which will automatically run with the release profile. Times were achieved on an Apple Macbook Pro M1 Max with 8 performance and 2 efficiency cores, and with 32GB of RAM.

Of course, the use cases of Anvil and the RevmMiddleware can be different. Anvil represents a more realistic environment with networking and mining, while the RevmMiddleware is simpler environment with the bare essentials to running stateful simulations. Anvil also mines blocks for each transaction, while the RevmMiddleware does not. We hope to improve our API to allow the end user to be able to interface with their own choice of EVM environment to suit what ever their needs may be!

Please let us know if you find any issues with these benchmarks or if you have any suggestions on how to improve them!

Testing

If you contribute please write tests for any new code you write, To run the tests, you can run:

cargo test --all --all-features

Contributing

See our Contributing Guidelines