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Prod check (#61)

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chancharles92 2 years ago
committed by GitHub
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8281e7c877
No known key found for this signature in database GPG Key ID: 4AEE18F83AFDEB23
9 changed files with 456 additions and 70 deletions
  1. +1
    -1
      arithmetic/src/virtual_polynomial.rs
  2. +1
    -1
      hyperplonk/src/structs.rs
  3. +1
    -1
      pcs/src/structs.rs
  4. +4
    -1
      poly-iop/Cargo.toml
  5. +9
    -0
      poly-iop/src/errors.rs
  6. +246
    -64
      poly-iop/src/prod_check/mod.rs
  7. +192
    -0
      poly-iop/src/prod_check/util.rs
  8. +1
    -1
      poly-iop/src/structs.rs
  9. +1
    -1
      poly-iop/src/sum_check/mod.rs

+ 1
- 1
arithmetic/src/virtual_polynomial.rs

@ -52,7 +52,7 @@ pub struct VirtualPolynomial {
raw_pointers_lookup_table: HashMap<*const DenseMultilinearExtension<F>, usize>, raw_pointers_lookup_table: HashMap<*const DenseMultilinearExtension<F>, usize>,
} }
#[derive(Clone, Debug, Default, PartialEq, CanonicalSerialize)]
#[derive(Clone, Debug, Default, PartialEq, Eq, CanonicalSerialize)]
/// Auxiliary information about the multilinear polynomial /// Auxiliary information about the multilinear polynomial
pub struct VPAuxInfo<F: PrimeField> { pub struct VPAuxInfo<F: PrimeField> {
/// max number of multiplicands in each product /// max number of multiplicands in each product

+ 1
- 1
hyperplonk/src/structs.rs

@ -165,7 +165,7 @@ pub struct HyperPlonkVerifyingKey
/// id_w2 = 1 // second witness /// id_w2 = 1 // second witness
/// ///
/// NOTE: here coeff is a signed integer, instead of a field element /// NOTE: here coeff is a signed integer, instead of a field element
#[derive(Clone, Debug, Default, PartialEq)]
#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub struct CustomizedGates { pub struct CustomizedGates {
pub(crate) gates: Vec<(i64, Option<usize>, Vec<usize>)>, pub(crate) gates: Vec<(i64, Option<usize>, Vec<usize>)>,
} }

+ 1
- 1
pcs/src/structs.rs

@ -1,7 +1,7 @@
use ark_ec::PairingEngine; use ark_ec::PairingEngine;
use ark_serialize::{CanonicalDeserialize, CanonicalSerialize, Read, SerializationError, Write}; use ark_serialize::{CanonicalDeserialize, CanonicalSerialize, Read, SerializationError, Write};
#[derive(CanonicalSerialize, CanonicalDeserialize, Clone, Debug, Default, PartialEq)]
#[derive(CanonicalSerialize, CanonicalDeserialize, Clone, Debug, Default, PartialEq, Eq)]
/// A commitment is an Affine point. /// A commitment is an Affine point.
pub struct Commitment<E: PairingEngine> { pub struct Commitment<E: PairingEngine> {
/// the actual commitment is an affine point. /// the actual commitment is an affine point.

+ 4
- 1
poly-iop/Cargo.toml

@ -6,12 +6,14 @@ edition = "2021"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies] [dependencies]
pcs = { path = "../pcs" }
ark-ff = { version = "^0.3.0", default-features = false } ark-ff = { version = "^0.3.0", default-features = false }
ark-std = { version = "^0.3.0", default-features = false } ark-std = { version = "^0.3.0", default-features = false }
ark-poly = { version = "^0.3.0", default-features = false } ark-poly = { version = "^0.3.0", default-features = false }
ark-serialize = { version = "^0.3.0", default-features = false } ark-serialize = { version = "^0.3.0", default-features = false }
ark-bls12-381 = { version = "0.3.0", default-features = false, features = [ "curve" ] } ark-bls12-381 = { version = "0.3.0", default-features = false, features = [ "curve" ] }
ark-ec = { version = "^0.3.0", default-features = false }
rand_chacha = { version = "0.3.0", default-features = false } rand_chacha = { version = "0.3.0", default-features = false }
displaydoc = { version = "0.2.3", default-features = false } displaydoc = { version = "0.2.3", default-features = false }
@ -37,7 +39,8 @@ parallel = [
"arithmetic/parallel", "arithmetic/parallel",
"ark-std/parallel", "ark-std/parallel",
"ark-ff/parallel", "ark-ff/parallel",
"ark-poly/parallel"
"ark-poly/parallel",
"pcs/parallel",
] ]
print-trace = [ print-trace = [
"arithmetic/print-trace", "arithmetic/print-trace",

+ 9
- 0
poly-iop/src/errors.rs

@ -3,6 +3,7 @@
use arithmetic::ArithErrors; use arithmetic::ArithErrors;
use ark_std::string::String; use ark_std::string::String;
use displaydoc::Display; use displaydoc::Display;
use pcs::prelude::PCSErrors;
use transcript::TranscriptErrors; use transcript::TranscriptErrors;
/// A `enum` specifying the possible failure modes of the PolyIOP. /// A `enum` specifying the possible failure modes of the PolyIOP.
@ -26,6 +27,8 @@ pub enum PolyIOPErrors {
TranscriptErrors(TranscriptErrors), TranscriptErrors(TranscriptErrors),
/// Arithmetic Error: {0} /// Arithmetic Error: {0}
ArithmeticErrors(ArithErrors), ArithmeticErrors(ArithErrors),
/// PCS error {0}
PCSErrors(PCSErrors),
} }
impl From<ark_serialize::SerializationError> for PolyIOPErrors { impl From<ark_serialize::SerializationError> for PolyIOPErrors {
@ -45,3 +48,9 @@ impl From for PolyIOPErrors {
Self::ArithmeticErrors(e) Self::ArithmeticErrors(e)
} }
} }
impl From<PCSErrors> for PolyIOPErrors {
fn from(e: PCSErrors) -> Self {
Self::PCSErrors(e)
}
}

+ 246
- 64
poly-iop/src/prod_check/mod.rs

@ -1,37 +1,49 @@
//! Main module for the Permutation Check protocol
//! Main module for the Product Check protocol
use crate::{errors::PolyIOPErrors, ZeroCheck};
use arithmetic::VirtualPolynomial;
use ark_ff::PrimeField;
use crate::{
errors::PolyIOPErrors,
prod_check::util::{compute_product_poly, prove_zero_check},
PolyIOP, ZeroCheck,
};
use arithmetic::VPAuxInfo;
use ark_ec::PairingEngine;
use ark_ff::{One, PrimeField, Zero};
use ark_poly::DenseMultilinearExtension; use ark_poly::DenseMultilinearExtension;
use ark_std::{end_timer, start_timer};
use pcs::prelude::PolynomialCommitmentScheme;
use std::{marker::PhantomData, rc::Rc};
use transcript::IOPTranscript; use transcript::IOPTranscript;
/// A ProductCheck is derived from ZeroCheck.
///
/// A ProductCheck IOP takes the following steps:
mod util;
/// A product-check proves that two n-variate multilinear polynomials `f(x),
/// g(x)` satisfy:
/// \prod_{x \in {0,1}^n} f(x) = \prod_{x \in {0,1}^n} g(x)
/// ///
/// Inputs:
/// - f(x)
/// A ProductCheck is derived from ZeroCheck.
/// ///
/// Prover steps: /// Prover steps:
/// 1. `compute_product_poly` to build `prod(x0, ..., x_n)` from virtual
/// polynomial f
/// 2. push commitments of `f(x)`, `prod(x)` to the transcript
/// (done by the snark caller)
/// 3. `generate_challenge` from current transcript (generate alpha)
/// 4. `prove` to generate the zerocheck proof for the virtual polynomial
/// prod(1, x) - prod(x, 0) * prod(x, 1) + alpha * (f(x) - prod(0, x))
/// 1. build `prod(x0, ..., x_n)` from f and g,
/// such that `prod(0, x1, ..., xn)` equals `f/g` over domain {0,1}^n
/// 2. push commitments of `prod(x)` to the transcript,
/// and `generate_challenge` from current transcript (generate alpha)
/// 3. generate the zerocheck proof for the virtual polynomial
/// prod(1, x) - prod(x, 0) * prod(x, 1) + alpha * (f(x) - prod(0, x) * g(x))
/// ///
/// Verifier steps: /// Verifier steps:
/// 1. Extract commitments of `f(x)`, `prod(x)` from the proof, push them to the
/// transcript (done by the snark caller)
/// 1. Extract commitments of `prod(x)` from the proof, push
/// them to the transcript
/// 2. `generate_challenge` from current transcript (generate alpha) /// 2. `generate_challenge` from current transcript (generate alpha)
/// 3. `verify` to verify the zerocheck proof and generate the subclaim for /// 3. `verify` to verify the zerocheck proof and generate the subclaim for
/// polynomial evaluations /// polynomial evaluations
pub trait ProductCheck<F: PrimeField>: ZeroCheck<F> {
pub trait ProductCheck<E, PCS>: ZeroCheck<E::Fr>
where
E: PairingEngine,
PCS: PolynomialCommitmentScheme<E>,
{
type ProductCheckSubClaim; type ProductCheckSubClaim;
type ProductCheckChallenge;
type ProductProof; type ProductProof;
type Polynomial;
/// Initialize the system with a transcript /// Initialize the system with a transcript
/// ///
@ -41,58 +53,44 @@ pub trait ProductCheck: ZeroCheck {
/// ProductCheck prover/verifier. /// ProductCheck prover/verifier.
fn init_transcript() -> Self::Transcript; fn init_transcript() -> Self::Transcript;
/// Generate random challenge `alpha` from a transcript.
fn generate_challenge(
transcript: &mut Self::Transcript,
) -> Result<Self::ProductCheckChallenge, PolyIOPErrors>;
/// Compute the product polynomial `prod(x)` where
///
/// - `prod(0,x) := prod(0, x1, …, xn)` is the MLE over the
/// evaluations of `f(x)` on the boolean hypercube {0,1}^n
///
/// - `prod(1,x)` is a MLE over the evaluations of `prod(x, 0) * prod(x, 1)`
/// on the boolean hypercube {0,1}^n
///
/// The caller needs to check num_vars matches in f
/// Cost: linear in N.
fn compute_product_poly(
fx: &VirtualPolynomial<F>,
) -> Result<DenseMultilinearExtension<F>, PolyIOPErrors>;
/// Initialize the prover to argue that for a virtual polynomial f(x),
/// it holds that `s = \prod_{x \in {0,1}^n} f(x)`
/// Generate a proof for product check, showing that witness multilinear
/// polynomials f(x), g(x) satisfy `\prod_{x \in {0,1}^n} f(x) =
/// \prod_{x \in {0,1}^n} g(x)`
/// ///
/// Inputs: /// Inputs:
/// - fx: the virtual polynomial
/// - prod_x: the product polynomial
/// - transcript: a transcript that is used to generate the challenges alpha
/// - claimed_product: the claimed product value
/// - fx: the numerator multilinear polynomial
/// - gx: the denominator multilinear polynomial
/// - transcript: the IOP transcript
/// - pk: PCS committing key
///
/// Outputs
/// - the product check proof
/// - the product polynomial (used for testing)
/// ///
/// Cost: O(N) /// Cost: O(N)
fn prove( fn prove(
fx: &VirtualPolynomial<F>,
prod_x: &DenseMultilinearExtension<F>,
transcript: &mut IOPTranscript<F>,
claimed_product: F,
) -> Result<Self::ProductProof, PolyIOPErrors>;
/// Verify that for a witness virtual polynomial f(x),
/// it holds that `s = \prod_{x \in {0,1}^n} f(x)`
fx: &Self::Polynomial,
gx: &Self::Polynomial,
transcript: &mut IOPTranscript<E::Fr>,
pk: &PCS::ProverParam,
) -> Result<(Self::ProductProof, Self::Polynomial), PolyIOPErrors>;
/// Verify that for witness multilinear polynomials f(x), g(x)
/// it holds that `\prod_{x \in {0,1}^n} f(x) = \prod_{x \in {0,1}^n} g(x)`
fn verify( fn verify(
proof: &Self::ProductProof, proof: &Self::ProductProof,
aux_info: &Self::VPAuxInfo,
num_vars: usize,
transcript: &mut Self::Transcript, transcript: &mut Self::Transcript,
claimed_product: F,
) -> Result<Self::ProductCheckSubClaim, PolyIOPErrors>; ) -> Result<Self::ProductCheckSubClaim, PolyIOPErrors>;
} }
/// A product check subclaim consists of /// A product check subclaim consists of
/// - A zero check IOP subclaim for /// - A zero check IOP subclaim for
/// `Q(x) = prod(1, x) - prod(x, 0) * prod(x, 1) + alpha * (f(x) - prod(0, x)`
/// is 0, consists of the following:
/// `Q(x) = prod(1, x) - prod(x, 0) * prod(x, 1) + challenge * (f(x) - prod(0,
/// x) * g(x))` is 0, consists of the following:
/// - the SubClaim from the SumCheck /// - the SubClaim from the SumCheck
/// - the initial challenge r which is used to build eq(x, r) in ZeroCheck /// - the initial challenge r which is used to build eq(x, r) in ZeroCheck
/// - The challenge `challenge`
/// - A final query for `prod(1, ..., 1, 0) = claimed_product`. /// - A final query for `prod(1, ..., 1, 0) = claimed_product`.
// Note that this final query is in fact a constant that // Note that this final query is in fact a constant that
// is independent from the proof. So we should avoid // is independent from the proof. So we should avoid
@ -102,16 +100,200 @@ pub struct ProductCheckSubClaim> {
// the SubClaim from the ZeroCheck // the SubClaim from the ZeroCheck
zero_check_sub_claim: ZC::ZeroCheckSubClaim, zero_check_sub_claim: ZC::ZeroCheckSubClaim,
// final query which consists of // final query which consists of
// - the vector `(1, ..., 1, 0)`
// - the evaluation `claimed_product`
// - the vector `(1, ..., 1, 0)` (needs to be reversed because Arkwork's MLE uses big-endian
// format for points)
// The expected final query evaluation is 1
final_query: (Vec<F>, F), final_query: (Vec<F>, F),
challenge: F,
} }
/// The random challenges in a product check protocol
#[allow(dead_code)]
pub struct ProductCheckChallenge<F: PrimeField> {
alpha: F,
/// A product check proof consists of
/// - a zerocheck proof
/// - a product polynomial commitment
#[derive(Clone, Debug, Default, PartialEq)]
pub struct ProductProof<E: PairingEngine, PCS: PolynomialCommitmentScheme<E>, ZC: ZeroCheck<E::Fr>>
{
zero_check_proof: ZC::ZeroCheckProof,
prod_x_comm: PCS::Commitment,
}
impl<E, PCS> ProductCheck<E, PCS> for PolyIOP<E::Fr>
where
E: PairingEngine,
PCS: PolynomialCommitmentScheme<E, Polynomial = Rc<DenseMultilinearExtension<E::Fr>>>,
{
type ProductCheckSubClaim = ProductCheckSubClaim<E::Fr, Self>;
type ProductProof = ProductProof<E, PCS, Self>;
type Polynomial = Rc<DenseMultilinearExtension<E::Fr>>;
fn init_transcript() -> Self::Transcript {
IOPTranscript::<E::Fr>::new(b"Initializing ProductCheck transcript")
}
fn prove(
fx: &Self::Polynomial,
gx: &Self::Polynomial,
transcript: &mut IOPTranscript<E::Fr>,
pk: &PCS::ProverParam,
) -> Result<(Self::ProductProof, Self::Polynomial), PolyIOPErrors> {
let start = start_timer!(|| "prod_check prove");
if fx.num_vars != gx.num_vars {
return Err(PolyIOPErrors::InvalidParameters(
"fx and gx have different number of variables".to_string(),
));
}
// compute the product polynomial
let prod_x = compute_product_poly(fx, gx)?;
// generate challenge
let prod_x_comm = PCS::commit(pk, &Rc::new(prod_x.clone()))?;
transcript.append_serializable_element(b"prod(x)", &prod_x_comm)?;
let alpha = transcript.get_and_append_challenge(b"alpha")?;
// build the zero-check proof
let (zero_check_proof, _) = prove_zero_check(fx, gx, &prod_x, &alpha, transcript)?;
end_timer!(start);
Ok((
ProductProof {
zero_check_proof,
prod_x_comm,
},
Rc::new(prod_x.clone()),
))
}
fn verify(
proof: &Self::ProductProof,
num_vars: usize,
transcript: &mut Self::Transcript,
) -> Result<Self::ProductCheckSubClaim, PolyIOPErrors> {
let start = start_timer!(|| "prod_check verify");
// update transcript and generate challenge
transcript.append_serializable_element(b"prod(x)", &proof.prod_x_comm)?;
let alpha = transcript.get_and_append_challenge(b"alpha")?;
// invoke the zero check on the iop_proof
// the virtual poly info for Q(x)
let aux_info = VPAuxInfo {
max_degree: 2,
num_variables: num_vars,
phantom: PhantomData::default(),
};
let zero_check_sub_claim =
<Self as ZeroCheck<E::Fr>>::verify(&proof.zero_check_proof, &aux_info, transcript)?;
// the final query is on prod_x, hence has length `num_vars` + 1
let mut final_query = vec![E::Fr::one(); aux_info.num_variables + 1];
// the point has to be reversed because Arkworks uses big-endian.
final_query[0] = E::Fr::zero();
let final_eval = E::Fr::one();
end_timer!(start);
Ok(ProductCheckSubClaim {
zero_check_sub_claim,
final_query: (final_query, final_eval),
challenge: alpha,
})
}
} }
#[cfg(test)] #[cfg(test)]
mod test {}
mod test {
use super::ProductCheck;
use crate::{errors::PolyIOPErrors, PolyIOP};
use ark_bls12_381::{Bls12_381, Fr};
use ark_ec::PairingEngine;
use ark_poly::{DenseMultilinearExtension, MultilinearExtension};
use ark_std::test_rng;
use pcs::{prelude::KZGMultilinearPCS, PolynomialCommitmentScheme};
use std::rc::Rc;
// f and g are guaranteed to have the same product
fn test_product_check_helper<E, PCS>(
f: &DenseMultilinearExtension<E::Fr>,
g: &DenseMultilinearExtension<E::Fr>,
pk: &PCS::ProverParam,
) -> Result<(), PolyIOPErrors>
where
E: PairingEngine,
PCS: PolynomialCommitmentScheme<E, Polynomial = Rc<DenseMultilinearExtension<E::Fr>>>,
{
let mut transcript = <PolyIOP<E::Fr> as ProductCheck<E, PCS>>::init_transcript();
transcript.append_message(b"testing", b"initializing transcript for testing")?;
let (proof, prod_x) = <PolyIOP<E::Fr> as ProductCheck<E, PCS>>::prove(
&Rc::new(f.clone()),
&Rc::new(g.clone()),
&mut transcript,
pk,
)?;
let mut transcript = <PolyIOP<E::Fr> as ProductCheck<E, PCS>>::init_transcript();
transcript.append_message(b"testing", b"initializing transcript for testing")?;
let subclaim =
<PolyIOP<E::Fr> as ProductCheck<E, PCS>>::verify(&proof, f.num_vars, &mut transcript)?;
assert_eq!(
prod_x.evaluate(&subclaim.final_query.0).unwrap(),
subclaim.final_query.1,
"different product"
);
// bad path
let mut transcript = <PolyIOP<E::Fr> as ProductCheck<E, PCS>>::init_transcript();
transcript.append_message(b"testing", b"initializing transcript for testing")?;
let h = f + g;
let (bad_proof, prod_x_bad) = <PolyIOP<E::Fr> as ProductCheck<E, PCS>>::prove(
&Rc::new(f.clone()),
&Rc::new(h.clone()),
&mut transcript,
pk,
)?;
let mut transcript = <PolyIOP<E::Fr> as ProductCheck<E, PCS>>::init_transcript();
transcript.append_message(b"testing", b"initializing transcript for testing")?;
let bad_subclaim = <PolyIOP<E::Fr> as ProductCheck<E, PCS>>::verify(
&bad_proof,
f.num_vars,
&mut transcript,
)?;
assert_ne!(
prod_x_bad.evaluate(&bad_subclaim.final_query.0).unwrap(),
bad_subclaim.final_query.1,
"can't detect wrong proof"
);
Ok(())
}
fn test_product_check(nv: usize) -> Result<(), PolyIOPErrors> {
let mut rng = test_rng();
let f: DenseMultilinearExtension<Fr> = DenseMultilinearExtension::rand(nv, &mut rng);
let mut g = f.clone();
g.evaluations.reverse();
let srs = KZGMultilinearPCS::<Bls12_381>::gen_srs_for_testing(&mut rng, nv + 1)?;
let (pk, _) = KZGMultilinearPCS::<Bls12_381>::trim(&srs, nv + 1, Some(nv + 1))?;
test_product_check_helper::<Bls12_381, KZGMultilinearPCS<Bls12_381>>(&f, &g, &pk)?;
Ok(())
}
#[test]
fn test_trivial_polynomial() -> Result<(), PolyIOPErrors> {
test_product_check(1)
}
#[test]
fn test_normal_polynomial() -> Result<(), PolyIOPErrors> {
test_product_check(10)
}
}

+ 192
- 0
poly-iop/src/prod_check/util.rs

@ -0,0 +1,192 @@
//! This module implements useful functions for the product check protocol.
use crate::{errors::PolyIOPErrors, structs::IOPProof, utils::get_index, PolyIOP, ZeroCheck};
use arithmetic::VirtualPolynomial;
use ark_ff::PrimeField;
use ark_poly::DenseMultilinearExtension;
use ark_std::{end_timer, start_timer};
use std::rc::Rc;
use transcript::IOPTranscript;
/// Compute the product polynomial `prod(x)` where
///
/// - `prod(0,x) := prod(0, x1, …, xn)` is the MLE over the
/// evaluations of `f(x)/g(x)` on the boolean hypercube {0,1}^n
///
/// - `prod(1,x)` is a MLE over the evaluations of `prod(x, 0) * prod(x, 1)`
/// on the boolean hypercube {0,1}^n
///
/// The caller needs to check num_vars matches in f and g
/// Cost: linear in N.
pub(super) fn compute_product_poly<F: PrimeField>(
fx: &DenseMultilinearExtension<F>,
gx: &DenseMultilinearExtension<F>,
) -> Result<DenseMultilinearExtension<F>, PolyIOPErrors> {
let start = start_timer!(|| "compute evaluations of prod polynomial");
let num_vars = fx.num_vars;
// ===================================
// prod(0, x)
// ===================================
let prod_0x_eval = compute_prod_0(fx, gx)?;
// ===================================
// prod(1, x)
// ===================================
//
// `prod(1, x)` can be computed via recursing the following formula for 2^n-1
// times
//
// `prod(1, x_1, ..., x_n) :=
// prod(x_1, x_2, ..., x_n, 0) * prod(x_1, x_2, ..., x_n, 1)`
//
// At any given step, the right hand side of the equation
// is available via either eval_0x or the current view of eval_1x
let mut prod_1x_eval = vec![];
for x in 0..(1 << num_vars) - 1 {
// sign will decide if the evaluation should be looked up from eval_0x or
// eval_1x; x_zero_index is the index for the evaluation (x_2, ..., x_n,
// 0); x_one_index is the index for the evaluation (x_2, ..., x_n, 1);
let (x_zero_index, x_one_index, sign) = get_index(x, num_vars);
if !sign {
prod_1x_eval.push(prod_0x_eval[x_zero_index] * prod_0x_eval[x_one_index]);
} else {
// sanity check: if we are trying to look up from the eval_1x table,
// then the target index must already exist
if x_zero_index >= prod_1x_eval.len() || x_one_index >= prod_1x_eval.len() {
return Err(PolyIOPErrors::ShouldNotArrive);
}
prod_1x_eval.push(prod_1x_eval[x_zero_index] * prod_1x_eval[x_one_index]);
}
}
// prod(1, 1, ..., 1) := 0
prod_1x_eval.push(F::zero());
// ===================================
// prod(x)
// ===================================
// prod(x)'s evaluation is indeed `e := [eval_0x[..], eval_1x[..]].concat()`
let eval = [prod_0x_eval.as_slice(), prod_1x_eval.as_slice()].concat();
let prod_x = DenseMultilinearExtension::from_evaluations_vec(num_vars + 1, eval);
end_timer!(start);
Ok(prod_x)
}
/// generate the zerocheck proof for the virtual polynomial
/// prod(1, x) - prod(x, 0) * prod(x, 1) + alpha * (f(x) - prod(0, x) * g(x))
///
/// Returns proof and Q(x) for testing purpose.
///
/// Cost: O(N)
pub(super) fn prove_zero_check<F: PrimeField>(
fx: &DenseMultilinearExtension<F>,
gx: &DenseMultilinearExtension<F>,
prod_x: &DenseMultilinearExtension<F>,
alpha: &F,
transcript: &mut IOPTranscript<F>,
) -> Result<(IOPProof<F>, VirtualPolynomial<F>), PolyIOPErrors> {
let start = start_timer!(|| "zerocheck in product check");
let prod_partial_evals = build_prod_partial_eval(prod_x)?;
let prod_0x = Rc::new(prod_partial_evals[0].clone());
let prod_1x = Rc::new(prod_partial_evals[1].clone());
let prod_x0 = Rc::new(prod_partial_evals[2].clone());
let prod_x1 = Rc::new(prod_partial_evals[3].clone());
let fx = Rc::new(fx.clone());
let gx = Rc::new(gx.clone());
// compute g(x) * prod(0, x) * alpha
let mut q_x = VirtualPolynomial::new_from_mle(gx, F::one());
q_x.mul_by_mle(prod_0x, *alpha)?;
// g(x) * prod(0, x) * alpha
// - f(x) * alpha
q_x.add_mle_list([fx], -*alpha)?;
// Q(x) := prod(1,x) - prod(x, 0) * prod(x, 1)
// + alpha * (
// g(x) * prod(0, x)
// - f(x))
q_x.add_mle_list([prod_x0, prod_x1], -F::one())?;
q_x.add_mle_list([prod_1x], F::one())?;
let iop_proof = <PolyIOP<F> as ZeroCheck<F>>::prove(&q_x, transcript)?;
end_timer!(start);
Ok((iop_proof, q_x))
}
/// Helper function of the IOP.
///
/// Input:
/// - prod(x)
///
/// Output: the following 4 polynomials
/// - prod(0, x)
/// - prod(1, x)
/// - prod(x, 0)
/// - prod(x, 1)
fn build_prod_partial_eval<F: PrimeField>(
prod_x: &DenseMultilinearExtension<F>,
) -> Result<[DenseMultilinearExtension<F>; 4], PolyIOPErrors> {
let start = start_timer!(|| "build partial prod polynomial");
let prod_x_eval = &prod_x.evaluations;
let num_vars = prod_x.num_vars - 1;
// prod(0, x)
let prod_0_x =
DenseMultilinearExtension::from_evaluations_slice(num_vars, &prod_x_eval[0..1 << num_vars]);
// prod(1, x)
let prod_1_x = DenseMultilinearExtension::from_evaluations_slice(
num_vars,
&prod_x_eval[1 << num_vars..1 << (num_vars + 1)],
);
// ===================================
// prod(x, 0) and prod(x, 1)
// ===================================
//
// now we compute eval_x0 and eval_x1
// eval_0x will be the odd coefficients of eval
// and eval_1x will be the even coefficients of eval
let mut eval_x0 = vec![];
let mut eval_x1 = vec![];
for (x, &prod_x) in prod_x_eval.iter().enumerate() {
if x & 1 == 0 {
eval_x0.push(prod_x);
} else {
eval_x1.push(prod_x);
}
}
let prod_x_0 = DenseMultilinearExtension::from_evaluations_vec(num_vars, eval_x0);
let prod_x_1 = DenseMultilinearExtension::from_evaluations_vec(num_vars, eval_x1);
end_timer!(start);
Ok([prod_0_x, prod_1_x, prod_x_0, prod_x_1])
}
/// Returns the evaluations of
/// - `prod(0,x) := prod(0, x1, …, xn)` which is the MLE over the
/// evaluations of f(x)/g(x) on the boolean hypercube {0,1}^n:
///
/// The caller needs to check num_vars matches in f/g
/// Cost: linear in N.
fn compute_prod_0<F: PrimeField>(
fx: &DenseMultilinearExtension<F>,
gx: &DenseMultilinearExtension<F>,
) -> Result<Vec<F>, PolyIOPErrors> {
let start = start_timer!(|| "compute prod(0,x)");
let mut prod_0x_evals = vec![];
for (&fi, &gi) in fx.iter().zip(gx.iter()) {
prod_0x_evals.push(fi / gi);
}
end_timer!(start);
Ok(prod_0x_evals)
}

+ 1
- 1
poly-iop/src/structs.rs

@ -16,7 +16,7 @@ pub struct IOPProof {
/// A message from the prover to the verifier at a given round /// A message from the prover to the verifier at a given round
/// is a list of evaluations. /// is a list of evaluations.
#[derive(Clone, Debug, Default, PartialEq, CanonicalSerialize)]
#[derive(Clone, Debug, Default, PartialEq, Eq, CanonicalSerialize)]
pub struct IOPProverMessage<F: PrimeField> { pub struct IOPProverMessage<F: PrimeField> {
pub(crate) evaluations: Vec<F>, pub(crate) evaluations: Vec<F>,
} }

+ 1
- 1
poly-iop/src/sum_check/mod.rs

@ -113,7 +113,7 @@ pub trait SumCheckVerifier {
/// A SumCheckSubClaim is a claim generated by the verifier at the end of /// A SumCheckSubClaim is a claim generated by the verifier at the end of
/// verification when it is convinced. /// verification when it is convinced.
#[derive(Clone, Debug, Default, PartialEq)]
#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub struct SumCheckSubClaim<F: PrimeField> { pub struct SumCheckSubClaim<F: PrimeField> {
/// the multi-dimensional point that this multilinear extension is evaluated /// the multi-dimensional point that this multilinear extension is evaluated
/// to /// to

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