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_bn254::{constraints::GVar, Bn254, Fr, G1Projective as Projective};
 20use ark_grumpkin::{constraints::GVar as GVar2, Projective as Projective2};
 21
 22use folding_schemes::commitment::{kzg::KZG, pedersen::Pedersen};
 23use folding_schemes::folding::nova::Nova;
 24use folding_schemes::frontend::FCircuit;
 25use folding_schemes::{Error, FoldingScheme};
 26mod utils;
 27use utils::init_nova_ivc_params;
 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) -> Result<Self, Error> {
 42        Ok(Self { _f: PhantomData })
 43    }
 44    fn state_len(&self) -> usize {
 45        1
 46    }
 47    fn external_inputs_len(&self) -> usize {
 48        0
 49    }
 50
 51    /// computes the next state values in place, assigning z_{i+1} into z_i, and computing the new
 52    /// z_{i+1}
 53    fn step_native(
 54        &self,
 55        _i: usize,
 56        z_i: Vec<F>,
 57        _external_inputs: Vec<F>,
 58    ) -> Result<Vec<F>, Error> {
 59        let out_bytes = Sha256::evaluate(&(), z_i[0].into_bigint().to_bytes_le()).unwrap();
 60        let out: Vec<F> = out_bytes.to_field_elements().unwrap();
 61
 62        Ok(vec![out[0]])
 63    }
 64
 65    /// generates the constraints for the step of F for the given z_i
 66    fn generate_step_constraints(
 67        &self,
 68        _cs: ConstraintSystemRef<F>,
 69        _i: usize,
 70        z_i: Vec<FpVar<F>>,
 71        _external_inputs: Vec<FpVar<F>>,
 72    ) -> Result<Vec<FpVar<F>>, SynthesisError> {
 73        let unit_var = UnitVar::default();
 74        let out_bytes = Sha256Gadget::evaluate(&unit_var, &z_i[0].to_bytes()?)?;
 75        let out = out_bytes.0.to_constraint_field()?;
 76        Ok(vec![out[0].clone()])
 77    }
 78}
 79
 80/// cargo test --example sha256
 81#[cfg(test)]
 82pub mod tests {
 83    use super::*;
 84    use ark_r1cs_std::{alloc::AllocVar, R1CSVar};
 85    use ark_relations::r1cs::ConstraintSystem;
 86
 87    // test to check that the Sha256FCircuit computes the same values inside and outside the circuit
 88    #[test]
 89    fn test_f_circuit() {
 90        let cs = ConstraintSystem::<Fr>::new_ref();
 91
 92        let circuit = Sha256FCircuit::<Fr>::new(()).unwrap();
 93        let z_i = vec![Fr::from(1_u32)];
 94
 95        let z_i1 = circuit.step_native(0, z_i.clone(), vec![]).unwrap();
 96
 97        let z_iVar = Vec::<FpVar<Fr>>::new_witness(cs.clone(), || Ok(z_i)).unwrap();
 98        let computed_z_i1Var = circuit
 99            .generate_step_constraints(cs.clone(), 0, z_iVar.clone(), vec![])
100            .unwrap();
101        assert_eq!(computed_z_i1Var.value().unwrap(), z_i1);
102    }
103}
104
105/// cargo run --release --example sha256
106fn main() {
107    let num_steps = 10;
108    let initial_state = vec![Fr::from(1_u32)];
109
110    let F_circuit = Sha256FCircuit::<Fr>::new(()).unwrap();
111
112    println!("Prepare Nova ProverParams & VerifierParams");
113    let (prover_params, verifier_params, _) = init_nova_ivc_params::<Sha256FCircuit<Fr>>(F_circuit);
114
115    /// The idea here is that eventually we could replace the next line chunk that defines the
116    /// `type NOVA = Nova<...>` by using another folding scheme that fulfills the `FoldingScheme`
117    /// trait, and the rest of our code would be working without needing to be updated.
118    type NOVA = Nova<
119        Projective,
120        GVar,
121        Projective2,
122        GVar2,
123        Sha256FCircuit<Fr>,
124        KZG<'static, Bn254>,
125        Pedersen<Projective2>,
126    >;
127
128    println!("Initialize FoldingScheme");
129    let mut folding_scheme = NOVA::init(&prover_params, F_circuit, initial_state.clone()).unwrap();
130
131    // compute a step of the IVC
132    for i in 0..num_steps {
133        let start = Instant::now();
134        folding_scheme.prove_step(vec![]).unwrap();
135        println!("Nova::prove_step {}: {:?}", i, start.elapsed());
136    }
137
138    let (running_instance, incoming_instance, cyclefold_instance) = folding_scheme.instances();
139
140    println!("Run the Nova's IVC verifier");
141    NOVA::verify(
142        verifier_params,
143        initial_state,
144        folding_scheme.state(), // latest state
145        Fr::from(num_steps as u32),
146        running_instance,
147        incoming_instance,
148        cyclefold_instance,
149    )
150    .unwrap();
151}