PLONK

This is a pure Rust implementation of the PLONK proving system over BLS12-381

This library contains a modularised implementation of KZG10 as the default polynomial commitment scheme.

Usage

use dusk_plonk::prelude::*;
use rand_core::OsRng;

// Implement a circuit that checks:
// 1) a + b = c where C is a PI
// 2) a <= 2^6
// 3) b <= 2^5
// 4) a * b = d where D is a PI
// 5) JubJub::GENERATOR * e(JubJubScalar) = f where F is a Public Input
#[derive(Debug, Default)]
pub struct TestCircuit {
    a: BlsScalar,
    b: BlsScalar,
    c: BlsScalar,
    d: BlsScalar,
    e: JubJubScalar,
    f: JubJubAffine,
}

impl Circuit for TestCircuit {
    const CIRCUIT_ID: [u8; 32] = [0xff; 32];
    fn gadget(
        &mut self,
        composer: &mut StandardComposer,
    ) -> Result<(), Error> {
        let a = composer.add_input(self.a);
        let b = composer.add_input(self.b);
        // Make first constraint a + b = c
        composer.poly_gate(
            a,
            b,
            composer.zero_var(),
            BlsScalar::zero(),
            BlsScalar::one(),
            BlsScalar::one(),
            BlsScalar::zero(),
            BlsScalar::zero(),
            Some(-self.c),
        );
        // Check that a and b are in range
        composer.range_gate(a, 1 << 6);
        composer.range_gate(b, 1 << 5);
        // Make second constraint a * b = d
        composer.poly_gate(
            a,
            b,
            composer.zero_var(),
            BlsScalar::one(),
            BlsScalar::zero(),
            BlsScalar::zero(),
            BlsScalar::one(),
            BlsScalar::zero(),
            Some(-self.d),
        );

        let e = composer.add_input(self.e.into());
        let scalar_mul_result = composer
            .fixed_base_scalar_mul(e, dusk_jubjub::GENERATOR_EXTENDED);
        // Apply the constrain
        composer.assert_equal_public_point(scalar_mul_result, self.f);
        Ok(())
    }
    fn padded_circuit_size(&self) -> usize {
        1 << 11
    }
}

// Now let's use the Circuit we've just implemented!

let pp = PublicParameters::setup(1 << 12, &mut OsRng).unwrap();
// Initialize the circuit
let mut circuit = TestCircuit::default();
// Compile the circuit
let (pk, vd) = circuit.compile(&pp).unwrap();
// Prover POV
let proof = {
    let mut circuit = TestCircuit {
        a: BlsScalar::from(20u64),
        b: BlsScalar::from(5u64),
        c: BlsScalar::from(25u64),
        d: BlsScalar::from(100u64),
        e: JubJubScalar::from(2u64),
        f: JubJubAffine::from(
            dusk_jubjub::GENERATOR_EXTENDED * JubJubScalar::from(2u64),
        ),
    };
    circuit.gen_proof(&pp, &pk, b"Test").unwrap()
};
// Verifier POV
let public_inputs: Vec<PublicInputValue> = vec![
    BlsScalar::from(25u64).into(),
    BlsScalar::from(100u64).into(),
    JubJubAffine::from(
        dusk_jubjub::GENERATOR_EXTENDED * JubJubScalar::from(2u64),
    )
    .into(),
];
circuit::verify_proof(
    &pp,
    &vd.key(),
    &proof,
    &public_inputs,
    &vd.pi_pos(),
    b"Test",
).unwrap();

Features

This crate includes a variety of features which will briefly be explained below:

• alloc: Enables the usage of an allocator and with it the capability of performing Proof constructions and verifications. Without this feature it IS NOT possible to prove or verify anything. Its absence only makes dusk-plonk export certain fixed-size data structures such as Proof which can be useful in no_std envoirments where we don't have allocators either.
• std: Enables std usage as well as rayon parallelisation in some proving and verifying ops. It also uses the std versions of the elliptic curve deps, which utilises the parallel feature from dusk-bls12-381. By default, this is the feature that comes enabled with the crate.
• trace: Enables the Circuit debugger tooling. This is essentially the capability of using the StandardComposer::check_circuit_satisfied function. The function will output information about each circuit gate until one of the gates does not satisfy the equation, or there are no more gates. If there is an unsatisfied gate equation, the function will panic and return the gate number.
• trace-print: Goes a step further than trace and prints each gate component data, giving a clear overview of all the values which make up the circuit that we're constructing. The recommended method is to derive the std output, and the std error, and then place them in text file which can be used to efficiently analyse the gates.
• canon: Enables canonical serialisation for particular data structures, which is very useful in integrating this library within the rest of the Dusk stack - especially for storage purposes.

Documentation

There are two main types of documentation in this repository:

• Crate documentation. This provides info about all of the functions that the library provides, as well as the documentation regarding the data structures that it exports. To check this, please feel free to go to the documentation page or run make doc or make doc-internal.

• Notes. This is a specific subset of documentation which explains the key mathematical concepts of PLONK and how they work with mathematical demonstrations. To check it, run make doc and open the resulting docs, which will be located under /target with your browser.

Performance

Benchmarks taken on Intel(R) Core(TM) i9-9900X CPU @ 3.50GHz For a circuit-size of 2^16 constraints/gates:

• Proving time: 5.46s
• Verification time: 9.34ms. (This time will not vary depending on the circuit-size.)

Acknowledgements

• Reference implementation AztecProtocol/Barretenberg
• FFT Module and KZG10 Module were taken and modified from zexe/zcash and scipr-lab, respectively.

Licensing

This code is licensed under Mozilla Public License Version 2.0 (MPL-2.0). Please see LICENSE for further info.

About

Implementation designed by the dusk team.

Contributing

• If you want to contribute to this repository/project please, check CONTRIBUTING.md
• If you want to report a bug or request a new feature addition, please open an issue on this repository.