Implement compute row kzg commitments

Fix related bugs

nomos-da/kzgrs-backend/src/encoder.rs

@@ -1,6 +1,7 @@
 use crate::common::{hash_column_and_commitment, Chunk, ChunksMatrix, Row};
 use crate::global::{DOMAIN, GLOBAL_PARAMETERS};
 use ark_poly::univariate::DensePolynomial;
+use kzgrs::common::bytes_to_polynomial_unchecked;
 use kzgrs::{
     bytes_to_polynomial, commit_polynomial, encode, generate_element_proof, Commitment,
     Evaluations, KzgRsError, Polynomial, Proof, BYTES_PER_FIELD_ELEMENT,
@@ -62,11 +63,15 @@ impl DaEncoder {
         matrix
             .rows()
             .map(|r| {
-                bytes_to_polynomial::<BYTES_PER_FIELD_ELEMENT>(r.as_bytes().as_ref(), *DOMAIN)
-                    .and_then(|(evals, poly)| {
-                        commit_polynomial(&poly, &GLOBAL_PARAMETERS)
-                            .map(|commitment| ((evals, poly), commitment))
-                    })
+                // Using the unchecked version here. Because during the process of chunkifiying
+                // we already make sure to have the chunks of proper elements.
+                // Also, after rs encoding, we are sure all `Fr` elements already fits within modulus.
+                let (evals, poly) = bytes_to_polynomial_unchecked::<BYTES_PER_FIELD_ELEMENT>(
+                    r.as_bytes().as_ref(),
+                    *DOMAIN,
+                );
+                commit_polynomial(&poly, &GLOBAL_PARAMETERS)
+                    .map(|commitment| ((evals, poly), commitment))
             })
             .collect()
     }
@@ -217,4 +222,12 @@ pub mod test {
             assert_eq!(row.0[0].len(), BYTES_PER_FIELD_ELEMENT);
         }
     }
+
+    #[test]
+    fn test_compute_row_kzg_commitments() {
+        let data = rand_data(32);
+        let matrix = ENCODER.chunkify(data.as_ref());
+        let commitments_data = DaEncoder::compute_kzg_row_commitments(&matrix).unwrap();
+        assert_eq!(commitments_data.len(), matrix.len());
+    }
 }

nomos-da/kzgrs/src/common.rs

@@ -1,6 +1,6 @@
 // std
 // crates
-use crate::Commitment;
+use crate::{Commitment, BYTES_PER_FIELD_ELEMENT};
 use ark_bls12_381::fr::Fr;
 use ark_ff::{BigInteger256, PrimeField, Zero};
 use ark_poly::domain::general::GeneralEvaluationDomain;
@@ -53,7 +53,7 @@ pub fn bytes_to_polynomial<const CHUNK_SIZE: usize>(
     data: &[u8],
     domain: GeneralEvaluationDomain<Fr>,
 ) -> Result<(Evaluations<Fr>, DensePolynomial<Fr>), KzgRsError> {
-    if CHUNK_SIZE >= 32 {
+    if CHUNK_SIZE > BYTES_PER_FIELD_ELEMENT {
         return Err(KzgRsError::ChunkSizeTooBig(CHUNK_SIZE));
     }
     if data.len() % CHUNK_SIZE != 0 {
@@ -62,9 +62,21 @@ pub fn bytes_to_polynomial<const CHUNK_SIZE: usize>(
             current_size: data.len(),
         });
     }
+    Ok(bytes_to_polynomial_unchecked::<CHUNK_SIZE>(data, domain))
+}
+
+/// Transform chunks of bytes (of size `CHUNK_SIZE`) into `Fr` which are considered evaluations of a
+/// polynomial. Then use FFT to transform that polynomial into coefficient form.
+/// No extra checks are done for the caller.
+/// Caller need to ensure that `CHUNK_SIZE` is not bigger than the underlying `Fr` element can be
+/// decoded from.
+pub fn bytes_to_polynomial_unchecked<const CHUNK_SIZE: usize>(
+    data: &[u8],
+    domain: GeneralEvaluationDomain<Fr>,
+) -> (Evaluations<Fr>, DensePolynomial<Fr>) {
     let evals = bytes_to_evaluations::<CHUNK_SIZE>(data, domain);
     let coefficients = evals.interpolate_by_ref();
-    Ok((evals, coefficients))
+    (evals, coefficients)
 }
 
 #[cfg(test)]