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data_structures.rs
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data_structures.rs
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use crate::*;
use crate::{PCCommitterKey, PCVerifierKey, Vec};
use ark_ec::AffineCurve;
use ark_ff::{Field, ToBytes, UniformRand, Zero};
use ark_std::vec;
use rand_core::RngCore;
/// `UniversalParams` are the universal parameters for the inner product arg scheme.
#[derive(Derivative)]
#[derivative(Default(bound = ""), Clone(bound = ""), Debug(bound = ""))]
pub struct UniversalParams<G: AffineCurve> {
/// The key used to commit to polynomials.
pub comm_key: Vec<G>,
/// Some group generator.
pub h: G,
/// Some group generator specifically used for hiding.
pub s: G,
}
impl<G: AffineCurve> PCUniversalParams for UniversalParams<G> {
fn max_degree(&self) -> usize {
self.comm_key.len() - 1
}
}
/// `CommitterKey` is used to commit to, and create evaluation proofs for, a given
/// polynomial.
#[derive(Derivative)]
#[derivative(
Default(bound = ""),
Hash(bound = ""),
Clone(bound = ""),
Debug(bound = "")
)]
pub struct CommitterKey<G: AffineCurve> {
/// The key used to commit to polynomials.
pub comm_key: Vec<G>,
/// A random group generator.
pub h: G,
/// A random group generator that is to be used to make
/// a commitment hiding.
pub s: G,
/// The maximum degree supported by the parameters
/// this key was derived from.
pub max_degree: usize,
}
impl<G: AffineCurve> PCCommitterKey for CommitterKey<G> {
fn max_degree(&self) -> usize {
self.max_degree
}
fn supported_degree(&self) -> usize {
self.comm_key.len() - 1
}
}
/// `VerifierKey` is used to check evaluation proofs for a given commitment.
pub type VerifierKey<G> = CommitterKey<G>;
impl<G: AffineCurve> PCVerifierKey for VerifierKey<G> {
fn max_degree(&self) -> usize {
self.max_degree
}
fn supported_degree(&self) -> usize {
self.comm_key.len() - 1
}
}
/// Nothing to do to prepare this verifier key (for now).
pub type PreparedVerifierKey<G> = VerifierKey<G>;
impl<G: AffineCurve> PCPreparedVerifierKey<VerifierKey<G>> for PreparedVerifierKey<G> {
/// prepare `PreparedVerifierKey` from `VerifierKey`
fn prepare(vk: &VerifierKey<G>) -> Self {
vk.clone()
}
}
/// Commitment to a polynomial that optionally enforces a degree bound.
#[derive(Derivative)]
#[derivative(
Default(bound = ""),
Hash(bound = ""),
Clone(bound = ""),
Copy(bound = ""),
Debug(bound = ""),
PartialEq(bound = ""),
Eq(bound = "")
)]
pub struct Commitment<G: AffineCurve> {
/// A Pedersen commitment to the polynomial.
pub comm: G,
/// A Pedersen commitment to the shifted polynomial.
/// This is `none` if the committed polynomial does not
/// enforce a strict degree bound.
pub shifted_comm: Option<G>,
}
impl<G: AffineCurve> PCCommitment for Commitment<G> {
#[inline]
fn empty() -> Self {
Commitment {
comm: G::zero(),
shifted_comm: None,
}
}
fn has_degree_bound(&self) -> bool {
false
}
fn size_in_bytes(&self) -> usize {
ark_ff::to_bytes![G::zero()].unwrap().len() / 2
}
}
impl<G: AffineCurve> ToBytes for Commitment<G> {
#[inline]
fn write<W: ark_std::io::Write>(&self, mut writer: W) -> ark_std::io::Result<()> {
self.comm.write(&mut writer)?;
let shifted_exists = self.shifted_comm.is_some();
shifted_exists.write(&mut writer)?;
self.shifted_comm
.as_ref()
.unwrap_or(&G::zero())
.write(&mut writer)
}
}
/// Nothing to do to prepare this commitment (for now).
pub type PreparedCommitment<E> = Commitment<E>;
impl<G: AffineCurve> PCPreparedCommitment<Commitment<G>> for PreparedCommitment<G> {
/// prepare `PreparedCommitment` from `Commitment`
fn prepare(vk: &Commitment<G>) -> Self {
vk.clone()
}
}
/// `Randomness` hides the polynomial inside a commitment and is outputted by `InnerProductArg::commit`.
#[derive(Derivative)]
#[derivative(
Default(bound = ""),
Hash(bound = ""),
Clone(bound = ""),
Debug(bound = ""),
PartialEq(bound = ""),
Eq(bound = "")
)]
pub struct Randomness<G: AffineCurve> {
/// Randomness is some scalar field element.
pub rand: G::ScalarField,
/// Randomness applied to the shifted commitment is some scalar field element.
pub shifted_rand: Option<G::ScalarField>,
}
impl<G: AffineCurve> PCRandomness for Randomness<G> {
fn empty() -> Self {
Self {
rand: G::ScalarField::zero(),
shifted_rand: None,
}
}
fn rand<R: RngCore>(_: usize, has_degree_bound: bool, _: Option<usize>, rng: &mut R) -> Self {
let rand = G::ScalarField::rand(rng);
let shifted_rand = if has_degree_bound {
Some(G::ScalarField::rand(rng))
} else {
None
};
Self { rand, shifted_rand }
}
}
/// `Proof` is an evaluation proof that is output by `InnerProductArg::open`.
#[derive(Derivative)]
#[derivative(
Default(bound = ""),
Hash(bound = ""),
Clone(bound = ""),
Debug(bound = "")
)]
pub struct Proof<G: AffineCurve> {
/// Vector of left elements for each of the log_d iterations in `open`
pub l_vec: Vec<G>,
/// Vector of right elements for each of the log_d iterations within `open`
pub r_vec: Vec<G>,
/// Committer key from the last iteration within `open`
pub final_comm_key: G,
/// Coefficient from the last iteration within withinopen`
pub c: G::ScalarField,
/// Commitment to the blinding polynomial.
pub hiding_comm: Option<G>,
/// Linear combination of all the randomness used for commitments
/// to the opened polynomials, along with the randomness used for the
/// commitment to the hiding polynomial.
pub rand: Option<G::ScalarField>,
}
impl<G: AffineCurve> PCProof for Proof<G> {
fn size_in_bytes(&self) -> usize {
ark_ff::to_bytes![self].unwrap().len()
}
}
impl<G: AffineCurve> ToBytes for Proof<G> {
#[inline]
fn write<W: ark_std::io::Write>(&self, mut writer: W) -> ark_std::io::Result<()> {
self.l_vec.write(&mut writer)?;
self.r_vec.write(&mut writer)?;
self.final_comm_key.write(&mut writer)?;
self.c.write(&mut writer)?;
self.hiding_comm
.as_ref()
.unwrap_or(&G::zero())
.write(&mut writer)?;
self.rand
.as_ref()
.unwrap_or(&G::ScalarField::zero())
.write(&mut writer)
}
}
/// `SuccinctCheckPolynomial` is a succinctly-representated polynomial
/// generated from the `log_d` random oracle challenges generated in `open`.
/// It has the special property that can be evaluated in `O(log_d)` time.
pub struct SuccinctCheckPolynomial<F: Field>(pub Vec<F>);
impl<F: Field> SuccinctCheckPolynomial<F> {
/// Computes the coefficients of the underlying degree `d` polynomial.
pub fn compute_coeffs(&self) -> Vec<F> {
let challenges = &self.0;
let log_d = challenges.len();
let mut coeffs = vec![F::one(); 1 << log_d];
for (i, challenge) in challenges.iter().enumerate() {
let i = i + 1;
let elem_degree = 1 << (log_d - i);
for start in (elem_degree..coeffs.len()).step_by(elem_degree * 2) {
for offset in 0..elem_degree {
coeffs[start + offset] *= challenge;
}
}
}
coeffs
}
/// Evaluate `self` at `point` in time `O(log_d)`.
pub fn evaluate(&self, point: F) -> F {
let challenges = &self.0;
let log_d = challenges.len();
let mut product = F::one();
for (i, challenge) in challenges.iter().enumerate() {
let i = i + 1;
let elem_degree: u64 = (1 << (log_d - i)) as u64;
let elem = point.pow([elem_degree]);
product *= &(F::one() + &(elem * challenge));
}
product
}
}