1#![allow(non_snake_case)]
  2#![allow(non_upper_case_globals)]
  3#![allow(non_camel_case_types)]
  4#![allow(clippy::upper_case_acronyms)]
  5
  6use ark_crypto_primitives::crh::{
  7    sha256::{
  8        constraints::{Sha256Gadget, UnitVar},
  9        Sha256,
 10    },
 11    CRHScheme, CRHSchemeGadget,
 12};
 13use ark_ff::{BigInteger, PrimeField, ToConstraintField};
 14use ark_r1cs_std::{fields::fp::FpVar, ToBytesGadget, ToConstraintFieldGadget};
 15use ark_relations::r1cs::{ConstraintSystemRef, SynthesisError};
 16use core::marker::PhantomData;
 17use std::time::Instant;
 18
 19use ark_pallas::{constraints::GVar, Fr, Projective};
 20use ark_vesta::{constraints::GVar as GVar2, Projective as Projective2};
 21
 22use folding_schemes::commitment::pedersen::Pedersen;
 23use folding_schemes::folding::nova::Nova;
 24use folding_schemes::frontend::FCircuit;
 25use folding_schemes::{Error, FoldingScheme};
 26mod utils;
 27use utils::test_nova_setup;
 28
 29/// This is the circuit that we want to fold, it implements the FCircuit trait.
 30/// The parameter z_i denotes the current state, and z_{i+1} denotes the next state which we get by
 31/// applying the step.
 32/// In this example we set z_i and z_{i+1} to be a single value, but the trait is made to support
 33/// arrays, so our state could be an array with different values.
 34#[derive(Clone, Copy, Debug)]
 35pub struct Sha256FCircuit<F: PrimeField> {
 36    _f: PhantomData<F>,
 37}
 38impl<F: PrimeField> FCircuit<F> for Sha256FCircuit<F> {
 39    type Params = ();
 40
 41    fn new(_params: Self::Params) -> Self {
 42        Self { _f: PhantomData }
 43    }
 44    fn state_len(self) -> usize {
 45        1
 46    }
 47
 48    /// computes the next state values in place, assigning z_{i+1} into z_i, and computing the new
 49    /// z_{i+1}
 50    fn step_native(self, z_i: Vec<F>) -> Result<Vec<F>, Error> {
 51        let out_bytes = Sha256::evaluate(&(), z_i[0].into_bigint().to_bytes_le()).unwrap();
 52        let out: Vec<F> = out_bytes.to_field_elements().unwrap();
 53
 54        Ok(vec![out[0]])
 55    }
 56
 57    /// generates the constraints for the step of F for the given z_i
 58    fn generate_step_constraints(
 59        self,
 60        _cs: ConstraintSystemRef<F>,
 61        z_i: Vec<FpVar<F>>,
 62    ) -> Result<Vec<FpVar<F>>, SynthesisError> {
 63        let unit_var = UnitVar::default();
 64        let out_bytes = Sha256Gadget::evaluate(&unit_var, &z_i[0].to_bytes()?)?;
 65        let out = out_bytes.0.to_constraint_field()?;
 66        Ok(vec![out[0].clone()])
 67    }
 68}
 69
 70/// cargo test --example sha256
 71#[cfg(test)]
 72pub mod tests {
 73    use super::*;
 74    use ark_r1cs_std::alloc::AllocVar;
 75    use ark_relations::r1cs::ConstraintSystem;
 76
 77    // test to check that the Sha256FCircuit computes the same values inside and outside the circuit
 78    #[test]
 79    fn test_sha256_f_circuit() {
 80        let cs = ConstraintSystem::<Fr>::new_ref();
 81
 82        let circuit = Sha256FCircuit::<Fr>::new(());
 83        let z_i = vec![Fr::from(1_u32)];
 84
 85        let z_i1 = circuit.step_native(z_i.clone()).unwrap();
 86
 87        let z_iVar = Vec::<FpVar<Fr>>::new_witness(cs.clone(), || Ok(z_i)).unwrap();
 88        let computed_z_i1Var = circuit
 89            .generate_step_constraints(cs.clone(), z_iVar.clone())
 90            .unwrap();
 91        assert_eq!(computed_z_i1Var.value().unwrap(), z_i1);
 92    }
 93}
 94
 95/// cargo run --release --example sha256
 96fn main() {
 97    let num_steps = 10;
 98    let initial_state = vec![Fr::from(1_u32)];
 99
100    let F_circuit = Sha256FCircuit::<Fr>::new(());
101
102    println!("Prepare Nova ProverParams & VerifierParams");
103    let (prover_params, verifier_params) = test_nova_setup::<Sha256FCircuit<Fr>>(F_circuit);
104
105    /// The idea here is that eventually we could replace the next line chunk that defines the
106    /// `type NOVA = Nova<...>` by using another folding scheme that fulfills the `FoldingScheme`
107    /// trait, and the rest of our code would be working without needing to be updated.
108    type NOVA = Nova<
109        Projective,
110        GVar,
111        Projective2,
112        GVar2,
113        Sha256FCircuit<Fr>,
114        Pedersen<Projective>,
115        Pedersen<Projective2>,
116    >;
117
118    println!("Initialize FoldingScheme");
119    let mut folding_scheme = NOVA::init(&prover_params, F_circuit, initial_state.clone()).unwrap();
120
121    // compute a step of the IVC
122    for i in 0..num_steps {
123        let start = Instant::now();
124        folding_scheme.prove_step().unwrap();
125        println!("Nova::prove_step {}: {:?}", i, start.elapsed());
126    }
127
128    let (running_instance, incomming_instance, cyclefold_instance) = folding_scheme.instances();
129
130    println!("Run the Nova's IVC verifier");
131    NOVA::verify(
132        verifier_params,
133        initial_state,
134        folding_scheme.state(), // latest state
135        Fr::from(num_steps as u32),
136        running_instance,
137        incomming_instance,
138        cyclefold_instance,
139    )
140    .unwrap();
141}