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Axiom Rust Circuit

warning

The Rust circuit SDK assumes more background in writing circuits with halo2-lib. We recommend using the Typescript SDK for most applications.

The Rust SDK allows you to write more complex circuits, fully utilizing the capabilities of halo2-lib.

Installation​

To install our Rust circuit SDK into a Cargo project, run:

cargo add axiom-sdk

Overview​

To implement an Axiom circuit using the Rust SDK you need to:

  • Specify an input struct that consists of native Rust types and ethers-rs types (ie. u64, Address, H256, etc.). The struct name must end with Input (ie. MyCircuitInput).
  • Implement the AxiomComputeFn trait on your input struct

Input Specification​

Your input struct can contain native Rust types (ie. u64, [usize; N], etc.) and ethers-rs types (ie. Address, H256, etc.), and its name must end with Input (ie. MyCircuitInput). Additional types can be used if they implement the RawInput trait (see here). The struct must be annotated with the #[AxiomComputeInput] attribute so that it implements the sufficient circuit traits. This attribute will also generate a new struct with Input replaced with CircuitInput (ie. AccountAgeInput -> AccountAgeCircuitInput), which has all the fields of the specified struct, but with halo2-lib types to be used inside your circuit (like AssignedValue<Fr>).

Here is an example:

#[AxiomComputeInput]
pub struct AccountAgeInput {
    pub addr: Address,
    pub claimed_block_number: u64,
}

Compute Function Specification​

You must implement the AxiomComputeFn on your input struct. There is only one trait function that you must implement:

fn compute(
    api: &mut AxiomAPI,
    assigned_inputs: AccountAgeCircuitInput<AssignedValue<Fr>>,
) -> Vec<AxiomResult>

where AccountAgeCircuitInput should be replaced with your derived circuit input struct.

The AxiomAPI struct gives you access to subquery calling functions in addition to a RlcCircuitBuilder to specify your circuit. Your compute function should then return any values that you wish to pass on-chain in the Vec<AxiomResult> -- an AxiomResult is either an enum of either HiLo<AssignedValue<Fr>> or AssignedValue<Fr> (in which case it is converted to hi-lo for you).

Here is an example:

impl AxiomComputeFn for AccountAgeInput {
    fn compute(
        api: &mut AxiomAPI,
        assigned_inputs: AccountAgeCircuitInput<AssignedValue<Fr>>,
    ) -> Vec<AxiomResult> {
        let gate = GateChip::new();
        let zero = api.ctx().load_zero();
        let one = api.ctx().load_constant(Fr::one());
        let prev_block = gate.sub(api.ctx(), assigned_inputs.claimed_block_number, one);

        let account_prev_block = api.get_account(prev_block, assigned_inputs.addr);
        let prev_nonce = account_prev_block.call(AccountField::Nonce);
        let prev_nonce = api.from_hi_lo(prev_nonce);
        api.ctx().constrain_equal(&prev_nonce, &zero);

        let account = api.get_account(assigned_inputs.claimed_block_number, assigned_inputs.addr);
        let curr_nonce = account.call(AccountField::Nonce);
        let curr_nonce = api.from_hi_lo(curr_nonce);

        api.range.check_less_than(api.ctx(), zero, curr_nonce, 40);

        vec![
            assigned_inputs.addr.into(),
            assigned_inputs.claimed_block_number.into(),
        ]
    }
}

Running The Circuit​

To run your circuit, create a main function call the run_cli function with your input struct as the generic parameter:

fn main() {
    env_logger::init();
    run_cli::<AccountAgeInput>();
}

The main function will run a CLI that allows you to run mock proving, key generation, and proving of your circuit. The CLI has the following commands:

Commands:
  mock    Run the mock prover
  keygen  Generate new proving & verifying keys
  prove   Generate a new proof
  run     Generate an Axiom compute query
  help    Print this message or the help of the given subcommand(s)

Options:
  -k, --degree <DEGREE>        To determine the size of your circuit (12..25)
  -p, --provider <PROVIDER>    JSON RPC provider URI
  -i, --input <INPUT_PATH>     JSON inputs to feed into your circuit
  -d, --data-path <DATA_PATH>  For saving build artifacts (optional)
  -c, --config <CONFIG>        For custom advanced usage only (optional)
  -h, --help                   Print help
  -V, --version                Print version

For example:

cargo run --example account_age -- --input data/account_age_input.json -k 12 -p <PROVIDER_URI> <CMD>

where PROVIDER_URI is a JSON-RPC URI, and CMD is mock, prove, keygen, or run.