w3f-pcs 0.0.6

Collection of tools for augmenting polynomial commitment schemes
Documentation 
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use ark_ec::pairing::Pairing;
use ark_ec::{AffineRepr, CurveGroup};
use ark_serialize::*;
use ark_std::iter::Sum;
use ark_std::ops::{Add, Mul, Sub};
use ark_std::vec::Vec;

use crate::pcs::Commitment;
use crate::utils::ec::small_multiexp_affine;

/// KZG commitment to G1 represented in affine coordinates.
#[derive(Clone, Debug, PartialEq, Eq, CanonicalSerialize, CanonicalDeserialize)]
pub struct KzgCommitment<E: Pairing>(pub E::G1Affine);

impl<E: Pairing> Mul<E::ScalarField> for KzgCommitment<E> {
    type Output = Self;

    fn mul(self, by: E::ScalarField) -> Self {
        (&self).mul(by)
    }
}

impl<E: Pairing> Commitment<E::ScalarField> for KzgCommitment<E> {
    fn mul(&self, by: E::ScalarField) -> KzgCommitment<E> {
        KzgCommitment(self.0.mul(by).into())
    }

    fn combine(coeffs: &[<E as Pairing>::ScalarField], commitments: &[Self]) -> Self {
        let bases = commitments.iter().map(|c| c.0).collect::<Vec<_>>();
        let prod = small_multiexp_affine(coeffs, &bases);
        KzgCommitment(prod.into())
    }
}

impl<E: Pairing> Add<Self> for KzgCommitment<E> {
    type Output = KzgCommitment<E>;

    fn add(self, other: KzgCommitment<E>) -> KzgCommitment<E> {
        KzgCommitment((self.0 + other.0).into_affine())
    }
}

impl<E: Pairing> Sub<Self> for KzgCommitment<E> {
    type Output = KzgCommitment<E>;

    fn sub(self, other: KzgCommitment<E>) -> KzgCommitment<E> {
        KzgCommitment((self.0 + -other.0.into_group()).into_affine())
    }
}

impl<E: Pairing> Sum<Self> for KzgCommitment<E> {
    fn sum<I: Iterator<Item = Self>>(iter: I) -> KzgCommitment<E> {
        KzgCommitment(iter.map(|c| c.0.into_group()).sum::<E::G1>().into_affine())
    }
}