add initial impl

Cargo.toml

@@ -9,6 +9,7 @@ members = [
     "eip7594",
     "cryptography/bls12_381",
     "cryptography/kzg_multi_open",
+    "cryptography/kzg_single_open",
     "cryptography/polynomial",
     "cryptography/erasure_codes",
 ]
@@ -32,6 +33,7 @@ polynomial = { package = "crate_crypto_internal_eth_kzg_polynomial", version = "
 erasure_codes = { package = "crate_crypto_internal_eth_kzg_erasure_codes", version = "0.4.1", path = "cryptography/erasure_codes" }
 rust_eth_kzg = { version = "0.4.1", path = "eip7594" }
 kzg_multi_open = { package = "crate_crypto_kzg_multi_open_fk20", version = "0.4.1", path = "cryptography/kzg_multi_open" }
+kzg_single_open = { package = "crate_crypto_kzg_single_open_fk20", version = "0.4.1", path = "cryptography/kzg_single_open" }
 c_eth_kzg = { version = "0.4.1", path = "bindings/c" }
 hex = "0.4.3"
 rayon = "1.10.0"

cryptography/kzg_single_open/Cargo.toml

@@ -0,0 +1,30 @@
+[package]
+name = "crate_crypto_kzg_single_open"
+description = "This crate provides an implementation for KZG10 suited for DAS in Ethereum"
+version = { workspace = true }
+authors = { workspace = true }
+edition = { workspace = true }
+license = { workspace = true }
+rust-version = { workspace = true }
+repository = { workspace = true }
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+bls12_381 = { workspace = true }
+polynomial = { workspace = true }
+hex = { workspace = true }
+rayon = { workspace = true }
+# We should not be importing this library here
+# We need it for the CommitKey
+kzg_multi_open = { workspace = true }
+pairing = { version = "0.23" }
+
+
+[dev-dependencies]
+criterion = "0.5.1"
+rand = "0.8.4"
+
+[[bench]]
+name = "benchmark"
+harness = false

cryptography/kzg_single_open/benches/benchmark.rs

@@ -0,0 +1,28 @@
+use bls12_381::Scalar;
+use bls12_381::{ff::Field, group::Group, G1Projective};
+use crate_crypto_kzg_single_open::compute_proof;
+use criterion::{criterion_group, criterion_main, Criterion};
+use kzg_multi_open::commit_key::CommitKey;
+use polynomial::domain::Domain;
+
+pub fn bench_single_opening_proof(c: &mut Criterion) {
+    const NUM_G1_ELEMENTS: usize = 4096;
+
+    let polynomial_4096: Vec<_> = (0..4096)
+        .into_iter()
+        .map(|i| -Scalar::from(i as u64))
+        .collect();
+    let G1s: Vec<_> = (0..NUM_G1_ELEMENTS)
+        .into_iter()
+        .map(|i| (G1Projective::generator() * (Scalar::from((i + 123456789) as u64))).into())
+        .collect();
+    let ck = CommitKey::new(G1s);
+    let rand_point = Scalar::random(&mut rand::thread_rng());
+    let domain = Domain::new(4096);
+    c.bench_function("compute single proof", |b| {
+        b.iter(|| compute_proof(&ck, &domain, &polynomial_4096, rand_point))
+    });
+}
+
+criterion_group!(benches, bench_single_opening_proof);
+criterion_main!(benches);

cryptography/kzg_single_open/src/lib.rs

@@ -0,0 +1,119 @@
+use bls12_381::{multi_pairings, G1Point, G2Point, G2Prepared, Scalar};
+use kzg_multi_open::{commit_key::CommitKey, opening_key::OpeningKey};
+use polynomial::{domain::Domain, monomial::PolyCoeff};
+
+pub struct Proof {
+    pub quotient_commitment: bls12_381::G1Point,
+    pub claimed_evaluation: Scalar,
+}
+
+/// Takes a polynomial in lagrange form in reverse bit order and an input point
+/// and computes a proof that the polynomial is correctly evaluated at the input point.
+///
+// Note: The total time taken is around 40-50ms on a single thread. 2-3ms of this is
+// division, fft and poly_eval. The rest of it is committing.
+pub fn compute_proof(
+    commit_key: &CommitKey,
+    domain: &Domain,
+    polynomial_lagrange: &[Scalar],
+    input_point: Scalar,
+) -> Proof {
+    // Bit reverse the polynomial and interpolate it.
+    //
+    // The bit-reversal is an artifact of a feature we want to maintain
+    // when we use FK20.
+    let mut poly_lagrange = polynomial_lagrange.to_vec();
+    reverse_bit_order(&mut poly_lagrange);
+    let polynomial_coeff = domain.ifft_scalars(poly_lagrange);
+
+    let quotient_poly = divide_by_linear(&polynomial_coeff, input_point);
+    let quotient_commitment = commit_key.commit_g1(quotient_poly.as_slice());
+    let claimed_evaluation = poly_eval(&polynomial_coeff, &input_point);
+
+    Proof {
+        quotient_commitment: quotient_commitment.into(),
+        claimed_evaluation,
+    }
+}
+
+pub(crate) fn reverse_bits(n: usize, bits: u32) -> usize {
+    let mut n = n;
+    let mut r = 0;
+    for _ in 0..bits {
+        r = (r << 1) | (n & 1);
+        n >>= 1;
+    }
+    r
+}
+
+/// Computes log2 of an integer.
+///
+/// Panics if the integer is not a power of two
+pub(crate) fn log2(x: u32) -> u32 {
+    assert!(x > 0 && x.is_power_of_two(), "x must be a power of two.");
+    x.trailing_zeros()
+}
+
+// Taken and modified from: https://github.com/filecoin-project/ec-gpu/blob/bdde768d0613ae546524c5612e2ad576a646e036/ec-gpu-gen/src/fft_cpu.rs#L10C8-L10C18
+pub fn reverse_bit_order<T>(a: &mut [T]) {
+    let n = a.len() as u32;
+    assert!(n.is_power_of_two(), "n must be a power of two");
+    let log_n = log2(n);
+
+    for k in 0..n {
+        let rk = reverse_bits(k as usize, log_n) as u32;
+        if k < rk {
+            a.swap(rk as usize, k as usize);
+        }
+    }
+}
+
+/// Checks that a polynomial `p` was evaluated at a point `z` and returned the value specified `y`.
+/// ie. y = p(z).
+pub fn verify(
+    opening_key: OpeningKey,
+    input_point: Scalar,
+    output_point: Scalar,
+    poly_comm: G1Point,
+    witness_comm: G1Point,
+) -> bool {
+    // For scalar muls could also do precomputations
+    let inner_a: G1Point = (poly_comm - (opening_key.g1s[0] * output_point)).into();
+    let inner_b: G2Point = (opening_key.g2s[1] - (opening_key.g2s[0] * input_point)).into();
+    let prepared_inner_b = G2Prepared::from(-inner_b);
+
+    let g2_gen_affine: G2Point = opening_key.g2s[0].into();
+    let prepared_g2_gen = G2Prepared::from(g2_gen_affine);
+
+    multi_pairings(&[
+        (&inner_a, &prepared_g2_gen),
+        (&witness_comm, &prepared_inner_b),
+    ])
+}
+
+pub fn poly_eval(poly: &PolyCoeff, value: &Scalar) -> Scalar {
+    let mut result = Scalar::from(0u64);
+    for coeff in poly.iter().rev() {
+        result = result * value + coeff;
+    }
+    result
+}
+
+/// Division using ruffini's rule
+fn divide_by_linear(poly: &[Scalar], z: Scalar) -> Vec<Scalar> {
+    let mut quotient: Vec<Scalar> = Vec::with_capacity(poly.len());
+    let mut k = Scalar::from(0u64);
+
+    for coeff in poly.iter().rev() {
+        let t = *coeff + k;
+        quotient.push(t);
+        k = z * t;
+    }
+
+    // Pop off the remainder term
+    quotient.pop();
+
+    // Reverse the results as monomial form stores coefficients starting with lowest degree
+    quotient.reverse();
+    quotient
+}