Public methods must accept raw bytes

Author: asn-d6

specs/_features/eip7594/polynomial-commitments-sampling.md

@@ -81,6 +81,18 @@ Cells are the smallest unit of blob data that can come with their own KZG proofs
 
 ## Helper functions
 
+### BLS12-381 helpers
+
+#### `bytes_to_cell`
+
+```python
+def bytes_to_cell(cell_bytes: Vector[Bytes32, FIELD_ELEMENTS_PER_CELL]) -> Cell:
+    """
+    Convert untrusted bytes into a Cell.
+    """
+    return [bytes_to_bls_field(element) for element in cell_bytes]
+```
+
 ### Linear combinations
 
 #### `g2_lincomb`
@@ -397,28 +409,32 @@ def compute_cells(blob: Blob) -> Vector[Cell, CELLS_PER_BLOB]:
 #### `verify_cell_proof`
 
 ```python
-def verify_cell_proof(commitment: KZGCommitment,
+def verify_cell_proof(commitment_bytes: Bytes48,
                       cell_id: int,
-                      cell: Cell,
-                      proof: KZGProof) -> bool:
+                      cell_bytes: Vector[Bytes32, FIELD_ELEMENTS_PER_CELL],
+                      proof: Bytes48) -> bool:
     """
     Check a cell proof
 
     Public method.
     """
     coset = coset_for_cell(cell_id)
 
-    return verify_kzg_proof_multi_impl(commitment, coset, cell, proof)
+    return verify_kzg_proof_multi_impl(
+        bytes_to_kzg_commitment(commitment_bytes),
+        coset,
+        bytes_to_cell(cell_bytes),
+        bytes_to_kzg_proof(proof))
 ```
 
 #### `verify_cell_proof_batch`
 
 ```python
-def verify_cell_proof_batch(row_commitments: Sequence[KZGCommitment],
+def verify_cell_proof_batch(row_commitments_bytes: Sequence[Bytes48],
                             row_ids: Sequence[int],
                             column_ids: Sequence[int],
-                            cells: Sequence[Cell],
-                            proofs: Sequence[KZGProof]) -> bool:
+                            cells_bytes: Sequence[Vector[Bytes32, FIELD_ELEMENTS_PER_CELL]],
+                            proofs_bytes: Sequence[Bytes48]) -> bool:
     """
     Check multiple cell proofs. This function implements the naive algorithm of checking every cell
     individually; an efficient algorithm can be found here:
@@ -430,10 +446,14 @@ def verify_cell_proof_batch(row_commitments: Sequence[KZGCommitment],
 
     Public method.
     """
-
     # Get commitments via row IDs
-    commitments = [row_commitments[row_id] for row_id in row_ids]
-    
+    commitments_bytes = [row_commitments_bytes[row_id] for row_id in row_ids]
+
+    # Get objects from bytes
+    commitments = [bytes_to_kzg_commitment(commitment_bytes) for commitment_bytes in commitments_bytes]
+    cells = [bytes_to_cell(cell_bytes) for cell_bytes in cells_bytes]
+    proofs = [bytes_to_kzg_proof(proof_bytes) for proof_bytes in proofs_bytes]
+
     return all(
         verify_kzg_proof_multi_impl(commitment, coset_for_cell(column_id), cell, proof)
         for commitment, column_id, cell, proof in zip(commitments, column_ids, cells, proofs)
@@ -445,7 +465,8 @@ def verify_cell_proof_batch(row_commitments: Sequence[KZGCommitment],
 ### `recover_polynomial`
 
 ```python
-def recover_polynomial(cell_ids: Sequence[CellID], cells: Sequence[Cell]) -> Polynomial:
+def recover_polynomial(cell_ids: Sequence[CellID],
+                       cells_bytes: Sequence[Vector[Bytes32, FIELD_ELEMENTS_PER_CELL]]) -> Polynomial:
     """
     Recovers a polynomial from 2 * FIELD_ELEMENTS_PER_CELL evaluations, half of which can be missing.
 
@@ -455,7 +476,10 @@ def recover_polynomial(cell_ids: Sequence[CellID], cells: Sequence[Cell]) -> Pol
 
     Public method.
     """
-    assert len(cell_ids) == len(cells)
+    assert len(cell_ids) == len(cells_bytes)
+
+    cells = [bytes_to_cell(cell_bytes) for cell_bytes in cells_bytes]
+
     assert len(cells) >= CELLS_PER_BLOB // 2
     missing_cell_ids = [cell_id for cell_id in range(CELLS_PER_BLOB) if cell_id not in cell_ids]
     roots_of_unity_reduced = compute_roots_of_unity(CELLS_PER_BLOB)

tests/core/pyspec/eth2spec/test/eip7594/unittests/polynomial_commitments/test_polynomial_commitments.py

@@ -10,6 +10,10 @@
 from eth2spec.utils.bls import BLS_MODULUS
 
 
+def field_element_bytes(x):
+    return int.to_bytes(x % BLS_MODULUS, 32, "big")
+
+
 @with_eip7594_and_later
 @spec_test
 @single_phase
@@ -34,10 +38,13 @@ def test_verify_cell_proof(spec):
     blob = get_sample_blob(spec)
     commitment = spec.blob_to_kzg_commitment(blob)
     cells, proofs = spec.compute_cells_and_proofs(blob)
+
+    cells_bytes = [[field_element_bytes(element) for element in cell] for cell in cells]
+
     cell_id = 0
-    assert spec.verify_cell_proof(commitment, cell_id, cells[cell_id], proofs[cell_id])
+    assert spec.verify_cell_proof(commitment, cell_id, cells_bytes[cell_id], proofs[cell_id])
     cell_id = 1
-    assert spec.verify_cell_proof(commitment, cell_id, cells[cell_id], proofs[cell_id])
+    assert spec.verify_cell_proof(commitment, cell_id, cells_bytes[cell_id], proofs[cell_id])
 
 
 @with_eip7594_and_later
@@ -48,12 +55,14 @@ def test_verify_cell_proof_batch(spec):
     commitment = spec.blob_to_kzg_commitment(blob)
     cells, proofs = spec.compute_cells_and_proofs(blob)
 
+    cells_bytes = [[field_element_bytes(element) for element in cell] for cell in cells]
+
     assert spec.verify_cell_proof_batch(
-        row_commitments=[commitment],
+        row_commitments_bytes=[commitment],
         row_ids=[0],
         column_ids=[0, 1],
-        cells=cells[0:1],
-        proofs=proofs,
+        cells_bytes=cells_bytes[0:1],
+        proofs_bytes=proofs,
     )
 
 
@@ -73,21 +82,21 @@ def test_recover_polynomial(spec):
 
     # Extend data with Reed-Solomon and split the extended data in cells
     cells = spec.compute_cells(blob)
+    cells_bytes = [[field_element_bytes(element) for element in cell] for cell in cells]
 
     # Compute the cells we will be recovering from
     cell_ids = []
-    known_cells = []
     # First figure out just the indices of the cells
     for i in range(N_SAMPLES):
         j = rng.randint(0, spec.CELLS_PER_BLOB)
         while j in cell_ids:
             j = rng.randint(0, spec.CELLS_PER_BLOB)
         cell_ids.append(j)
     # Now the cells themselves
-    known_cells = [cells[cell_id] for cell_id in cell_ids]
+    known_cells_bytes = [cells_bytes[cell_id] for cell_id in cell_ids]
 
     # Recover the data
-    recovered_data = spec.recover_polynomial(cell_ids, known_cells)
+    recovered_data = spec.recover_polynomial(cell_ids, known_cells_bytes)
 
     # Check that the original data match the non-extended portion of the recovered data
     assert original_polynomial == recovered_data[:len(recovered_data) // 2]