Added verification to certificate (#82)

* Added verification method to certificate

* Update da/common.py

typo short -> sort

Co-authored-by: gusto <bacv@users.noreply.github.com>

* Fix test imports

* Added verification comment

---------

Co-authored-by: gusto <bacv@users.noreply.github.com>

da/common.py

@@ -1,10 +1,10 @@
 from dataclasses import dataclass
-from itertools import chain, zip_longest
-from typing import List, Generator, Self
-
-
+from hashlib import sha3_256
+from itertools import chain, zip_longest, compress
+from typing import List, Generator, Self, Sequence
 
 from eth2spec.eip7594.mainnet import Bytes32, KZGCommitment as Commitment
+from py_ecc.bls import G2ProofOfPossession as bls_pop
 
 
 class NodeId(Bytes32):
@@ -55,3 +55,21 @@ class Certificate:
     aggregated_column_commitment: Commitment
     row_commitments: List[Commitment]
 
+    def verify(self, nodes_public_keys: List[BLSPublickey]) -> bool:
+        """
+        List of nodes public keys should be a trusted list of verified proof of possession keys.
+        Otherwise, we could fall under the Rogue Key Attack
+        `assert all(bls_pop.PopVerify(pk, proof) for pk, proof in zip(node_public_keys, pops))`
+        """
+        # we sort them as the signers bitfield is sorted by the public keys as well
+        signers_keys = list(compress(sorted(nodes_public_keys), self.signers))
+        message = build_attestation_message(self.aggregated_column_commitment, self.row_commitments)
+        return bls_pop.AggregateVerify(signers_keys, [message]*len(signers_keys), self.aggregated_signatures)
+
+
+def build_attestation_message(aggregated_column_commitment: Commitment, row_commitments: Sequence[Commitment]) -> bytes:
+    hasher = sha3_256()
+    hasher.update(bytes(aggregated_column_commitment))
+    for c in row_commitments:
+        hasher.update(bytes(c))
+    return hasher.digest()

da/dispersal.py

@@ -4,7 +4,7 @@ from typing import List, Optional, Generator, Sequence
 
 from py_ecc.bls import G2ProofOfPossession as bls_pop
 
-from da.common import Certificate, NodeId, BLSPublickey, Bitfield
+from da.common import Certificate, NodeId, BLSPublickey, Bitfield, build_attestation_message
 from da.encoder import EncodedData
 from da.verifier import DABlob, Attestation
 
@@ -19,9 +19,9 @@ class DispersalSettings:
 class Dispersal:
     def __init__(self, settings: DispersalSettings):
         self.settings = settings
-        # sort nodes_ids and related public keys
+        # sort over public keys
         self.settings.nodes_ids, self.settings.nodes_pubkey = zip(
-            *sorted(zip(self.settings.nodes_ids, self.settings.nodes_pubkey), key=lambda x: x[0])
+            *sorted(zip(self.settings.nodes_ids, self.settings.nodes_pubkey), key=lambda x: x[1])
         )
 
     def _prepare_data(self, encoded_data: EncodedData) -> Generator[DABlob, None, None]:
@@ -71,11 +71,7 @@ class Dispersal:
 
     @staticmethod
     def _build_attestation_message(encoded_data: EncodedData) -> bytes:
-        hasher = sha3_256()
-        hasher.update(bytes(encoded_data.aggregated_column_commitment))
-        for c in encoded_data.row_commitments:
-            hasher.update(bytes(c))
-        return hasher.digest()
+        return build_attestation_message(encoded_data.aggregated_column_commitment, encoded_data.row_commitments)
 
     def disperse(self, encoded_data: EncodedData) -> Optional[Certificate]:
         attestations = []

da/test_dispersal.py

@@ -1,14 +1,13 @@
 from hashlib import sha3_256
 from unittest import TestCase
 
-from .encoder import DAEncoderParams, DAEncoder
-from .test_encoder import TestEncoder
-
+from da.encoder import DAEncoderParams, DAEncoder
+from da.test_encoder import TestEncoder
+from da.verifier import DAVerifier, DABlob
 from da.common import NodeId, Attestation, Bitfield
 from da.dispersal import Dispersal, EncodedData, DispersalSettings
-from py_ecc.bls import G2ProofOfPossession as bls_pop
 
-from .verifier import DAVerifier, DABlob
+from py_ecc.bls import G2ProofOfPossession as bls_pop
 
 
 class TestDispersal(TestCase):
@@ -46,7 +45,7 @@ class TestDispersal(TestCase):
         self.assertEqual(certificate.row_commitments, [])
         self.assertIsNotNone(certificate.aggregated_signatures)
         self.assertTrue(
-            bls_pop.AggregateVerify(self.public_keys, [mock_message]*len(self.public_keys), certificate.aggregated_signatures)
+            certificate.verify(self.public_keys)
         )
 
     def test_disperse(self):
@@ -64,12 +63,7 @@ class TestDispersal(TestCase):
 
         certificate = self.dispersal.disperse(encoded_data)
         self.assertIsNotNone(certificate)
-        self.assertTrue(
-            bls_pop.AggregateVerify(
-                self.public_keys[:self.dispersal.settings.threshold],
-                [self.dispersal._build_attestation_message(encoded_data)]*self.dispersal.settings.threshold,
-                certificate.aggregated_signatures
-            )
+        self.assertTrue(certificate.verify(self.public_keys)
         )
         self.assertEqual(
             certificate.signers,