v9_r2_Challenges/300_zk-dirham/src/main.rs

use ark_ec::AffineRepr;
use ark_ff::PrimeField;
use ark_mnt4_753::{Fr as MNT4BigFr, MNT4_753};
use ark_mnt6_753::G1Affine;
use ark_mnt6_753::{constraints::G1Var, Fr as MNT6BigFr};

use ark_crypto_primitives::merkle_tree::{Config, MerkleTree, Path};
use ark_crypto_primitives::{crh::TwoToOneCRHScheme, snark::SNARK};
use ark_groth16::Groth16;
use ark_r1cs_std::fields::fp::FpVar;
use ark_r1cs_std::prelude::*;
use ark_relations::r1cs::{ConstraintSynthesizer, ConstraintSystemRef, SynthesisError};
use ark_serialize::{CanonicalDeserialize, Read};

use std::fs::File;
use std::io::Cursor;

pub mod poseidon_parameters;

type ConstraintF = MNT4BigFr;

use ark_crypto_primitives::{
    crh::{poseidon, *},
    merkle_tree::constraints::*,
    merkle_tree::*,
};
use ark_std::rand::SeedableRng;

type LeafH = poseidon::CRH<ConstraintF>;
type LeafHG = poseidon::constraints::CRHGadget<ConstraintF>;

type CompressH = poseidon::TwoToOneCRH<ConstraintF>;
type CompressHG = poseidon::constraints::TwoToOneCRHGadget<ConstraintF>;

type LeafVar = [FpVar<ConstraintF>];
struct MntMerkleTreeParamsVar;
impl ConfigGadget<MntMerkleTreeParams, ConstraintF> for MntMerkleTreeParamsVar {
    type Leaf = LeafVar;
    type LeafDigest = <LeafHG as CRHSchemeGadget<LeafH, ConstraintF>>::OutputVar;
    type LeafInnerConverter = IdentityDigestConverter<FpVar<ConstraintF>>;
    type InnerDigest = <CompressHG as TwoToOneCRHSchemeGadget<CompressH, ConstraintF>>::OutputVar;
    type LeafHash = LeafHG;
    type TwoToOneHash = CompressHG;
}

type MntMerkleTree = MerkleTree<MntMerkleTreeParams>;

struct MntMerkleTreeParams;

impl Config for MntMerkleTreeParams {
    type Leaf = [ConstraintF];

    type LeafDigest = <LeafH as CRHScheme>::Output;
    type LeafInnerDigestConverter = IdentityDigestConverter<ConstraintF>;
    type InnerDigest = <CompressH as TwoToOneCRHScheme>::Output;

    type LeafHash = LeafH;
    type TwoToOneHash = CompressH;
}

#[derive(Clone)]
struct SpendCircuit {
    pub leaf_params: <LeafH as CRHScheme>::Parameters,
    pub two_to_one_params: <LeafH as CRHScheme>::Parameters,
    pub root: <CompressH as TwoToOneCRHScheme>::Output,
    pub proof: Path<MntMerkleTreeParams>,
    pub secret: ConstraintF,
    pub nullifier: ConstraintF,
}

impl ConstraintSynthesizer<ConstraintF> for SpendCircuit {
    fn generate_constraints(
        self,
        cs: ConstraintSystemRef<ConstraintF>,
    ) -> Result<(), SynthesisError> {
        let root = <LeafHG as CRHSchemeGadget<LeafH, _>>::OutputVar::new_input(
            ark_relations::ns!(cs, "new_digest"),
            || Ok(self.root),
        )?;

        let leaf_crh_params_var =
            <LeafHG as CRHSchemeGadget<LeafH, _>>::ParametersVar::new_constant(
                ark_relations::ns!(cs, "leaf_crh_parameter"),
                &self.leaf_params,
            )?;
        let two_to_one_crh_params_var =
            <CompressHG as TwoToOneCRHSchemeGadget<CompressH, _>>::ParametersVar::new_constant(
                ark_relations::ns!(cs, "two_to_one_crh_parameter"),
                &self.two_to_one_params,
            )?;

        let secret = FpVar::new_witness(ark_relations::ns!(cs, "secret"), || Ok(self.secret))?;
        let secret_bits = secret.to_bits_le()?;
        Boolean::enforce_smaller_or_equal_than_le(&secret_bits, MNT6BigFr::MODULUS)?;

        let nullifier = <LeafHG as CRHSchemeGadget<LeafH, _>>::OutputVar::new_input(
            ark_relations::ns!(cs, "nullifier"),
            || Ok(self.nullifier),
        )?;

        let nullifier_in_circuit =
            <LeafHG as CRHSchemeGadget<LeafH, _>>::evaluate(&leaf_crh_params_var, &[secret])?;
        nullifier_in_circuit.enforce_equal(&nullifier)?;

        let base = G1Var::new_constant(ark_relations::ns!(cs, "base"), G1Affine::generator())?;
        let pk = base.scalar_mul_le(secret_bits.iter())?.to_affine()?;

        let leaf_g: Vec<_> = vec![pk.x];

        let cw: PathVar<MntMerkleTreeParams, ConstraintF, MntMerkleTreeParamsVar> =
            PathVar::new_witness(ark_relations::ns!(cs, "new_witness"), || Ok(&self.proof))?;

        cw.verify_membership(
            &leaf_crh_params_var,
            &two_to_one_crh_params_var,
            &root,
            &leaf_g,
        )?
        .enforce_equal(&Boolean::constant(true))?;

        Ok(())
    }
}

fn from_file<T: CanonicalDeserialize>(path: &str) -> T {
    let mut file = File::open(path).unwrap();
    let mut buffer = Vec::new();
    file.read_to_end(&mut buffer).unwrap();
    T::deserialize_uncompressed_unchecked(Cursor::new(&buffer)).unwrap()
}

fn main() {
    let rng = &mut ark_std::rand::rngs::StdRng::seed_from_u64(0u64);
    let leaves: Vec<Vec<MNT4BigFr>> = from_file("./leaves.bin");
    let leaked_secret: MNT4BigFr = from_file("./leaked_secret.bin");
    let (pk, vk): (
        <Groth16<MNT4_753> as SNARK<MNT4BigFr>>::ProvingKey,
        <Groth16<MNT4_753> as SNARK<MNT4BigFr>>::VerifyingKey,
    ) = from_file("./proof_keys.bin");
    let leaf_crh_params = poseidon_parameters::poseidon_parameters();
    let i = 2;
    let two_to_one_crh_params = leaf_crh_params.clone();
    let nullifier = <LeafH as CRHScheme>::evaluate(&leaf_crh_params, vec![leaked_secret]).unwrap();

    let tree = MntMerkleTree::new(
        &leaf_crh_params,
        &two_to_one_crh_params,
        leaves.iter().map(|x| x.as_slice()),
    )
    .unwrap();
    let root = tree.root();
    let leaf = &leaves[i];

    let tree_proof = tree.generate_proof(i).unwrap();
    assert!(tree_proof
        .verify(
            &leaf_crh_params,
            &two_to_one_crh_params,
            &root,
            leaf.as_slice()
        )
        .unwrap());

    let c = SpendCircuit {
        leaf_params: leaf_crh_params.clone(),
        two_to_one_params: two_to_one_crh_params.clone(),
        root: root.clone(),
        proof: tree_proof.clone(),
        nullifier: nullifier.clone(),
        secret: leaked_secret.clone(),
    };
    let proof = Groth16::<MNT4_753>::prove(&pk, c.clone(), rng).unwrap();
    assert!(Groth16::<MNT4_753>::verify(&vk, &vec![root, nullifier], &proof).unwrap());
}