nova-study/src/transcript.rs

use ark_ec::{AffineRepr, CurveGroup, Group};
use ark_ff::PrimeField;
use ark_serialize::CanonicalSerialize;
use std::marker::PhantomData;

use ark_r1cs_std::fields::fp::FpVar;

use ark_crypto_primitives::sponge::poseidon::{
    constraints::PoseidonSpongeVar, PoseidonConfig, PoseidonSponge,
};
use ark_crypto_primitives::sponge::{
    constraints::CryptographicSpongeVar, Absorb, CryptographicSponge,
};
use ark_relations::r1cs::{ConstraintSystemRef, SynthesisError};

use ark_poly::DenseUVPolynomial;

pub struct Transcript<F: PrimeField + Absorb, C: CurveGroup>
where
    <C as CurveGroup>::BaseField: Absorb,
{
    // where F is the Constraint Field (eq. C::ScalarField)
    sponge: PoseidonSponge<F>,
    _c: PhantomData<C>,
}
impl<F: PrimeField + Absorb, C: CurveGroup> Transcript<F, C>
where
    <C as CurveGroup>::BaseField: Absorb,
{
    pub fn new(poseidon_config: &PoseidonConfig<F>) -> Self {
        let mut sponge = PoseidonSponge::<F>::new(&poseidon_config);
        Transcript {
            sponge,
            _c: PhantomData,
        }
    }
    pub fn add(&mut self, v: &F) {
        self.sponge.absorb(&v);
    }
    pub fn add_vec(&mut self, v: &[F]) {
        self.sponge.absorb(&v);
    }
    pub fn add_point(&mut self, v: &C) {
        let v_affine = v.into_affine();
        let xy = v_affine.xy().unwrap(); // WIP
        self.sponge.absorb(&vec![xy.0, xy.1]);
    }
    pub fn get_challenge(&mut self) -> F {
        let c = self.sponge.squeeze_field_elements(1);
        self.add(&c[0]);
        c[0]
    }
    pub fn get_challenge_vec(&mut self, n: usize) -> Vec<F> {
        let c = self.sponge.squeeze_field_elements(n);
        self.sponge.absorb(&c);
        c
    }
}

pub struct TranscriptVar<F: PrimeField> {
    // where F is the Constraint Field
    sponge: PoseidonSpongeVar<F>,
}
impl<F: PrimeField> TranscriptVar<F> {
    pub fn new(cs: ConstraintSystemRef<F>, poseidon_config: PoseidonConfig<F>) -> Self {
        let mut sponge = PoseidonSpongeVar::<F>::new(cs.clone(), &poseidon_config);
        Self { sponge }
    }
    pub fn add(&mut self, v: FpVar<F>) -> Result<(), SynthesisError> {
        self.sponge.absorb(&v)
    }
    pub fn get_challenge(&mut self) -> Result<FpVar<F>, SynthesisError> {
        let c = self.sponge.squeeze_field_elements(1)?;
        self.sponge.absorb(&c[0]);
        Ok(c[0].clone())
    }
    pub fn get_challenge_vec(&mut self, n: usize) -> Result<Vec<FpVar<F>>, SynthesisError> {
        let c = self.sponge.squeeze_field_elements(n)?;
        self.sponge.absorb(&c);
        Ok(c)
    }
}

use ark_crypto_primitives::sponge::poseidon::find_poseidon_ark_and_mds;

// WARNING this is for test only
pub fn poseidon_test_config<F: PrimeField>() -> PoseidonConfig<F> {
    let full_rounds = 8;
    let partial_rounds = 31;
    let alpha = 5;
    let rate = 2;

    let (ark, mds) = find_poseidon_ark_and_mds::<F>(
        F::MODULUS_BIT_SIZE as u64,
        rate,
        full_rounds,
        partial_rounds,
        0,
    );

    PoseidonConfig::new(
        full_rounds as usize,
        partial_rounds as usize,
        alpha,
        mds,
        ark,
        rate,
        1,
    )
}

// #[cfg(test)]
// mod tests {
//     use super::*;
//     use ark_mnt4_298::{Fr, G1Projective}; // scalar field
//     use ark_std::{One, Zero};
//
//     #[test]
//     fn test_poseidon() {
//         let config = poseidon_test_config::<Fr>();
//         let mut tr = Transcript::<Fr, G1Projective>::new(&config);
//         tr.add(&Fr::one());
//         println!("c {:?}", tr.get_challenge().to_string());
//     }
// }