Adopt EIP-7688: Forward compatible consensus data structures

EIP-4788 exposes the beacon root to smart contracts, but smart contracts using it need to be redeployed / upgraded whenever the indexing changes during a fork, even if that fork does not touch any used functionality. This problem expands further to bridges on other blockchains, or even into wallet apps on a phone that verify data from the beacon chain instead of trusting the server. It is quite unrealistic to expect such projects to all align their release cadence with Ethereum's forks. EIP-7688 fixes this by defining forward compatibility for beacon chain data structures. Electra `Profile` retain their Merkleization even when rebased to `StableContainer` definitions from future forks, enabling decentralized protocols to drop the requirement for trusted parties to periodically upgrade beacon state proof verifiers. (+1 squashed commit) Squashed commits: [8b92f7b0f] Adopt EIP-7688: Forward compatible consensus data structures EIP-4788 exposes the beacon root to smart contracts, but smart contracts using it need to be redeployed / upgraded whenever the indexing changes during a fork, even if that fork does not touch any used functionality. This problem expands further to bridges on other blockchains, or even into wallet apps on a phone that verify data from the beacon chain instead of trusting the server. It is quite unrealistic to expect such projects to all align their release cadence with Ethereum's forks. EIP-7688 fixes this by defining forward compatibility for beacon chain data structures. Electra `Profile` retain their Merkleization even when rebased to `StableContainer` definitions from future forks, enabling decentralized protocols to drop the requirement for trusted parties to periodically upgrade beacon state proof verifiers.
ethereum · Jul 22, 2024 · 0abb4b6 · 0abb4b6
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diff --git a/presets/mainnet/electra.yaml b/presets/mainnet/electra.yaml
@@ -43,3 +43,8 @@ MAX_WITHDRAWAL_REQUESTS_PER_PAYLOAD: 16
 # ---------------------------------------------------------------
 # 2**3 ( = 8) pending withdrawals
 MAX_PENDING_PARTIALS_PER_WITHDRAWALS_SWEEP: 8
+
+# Misc
+# ---------------------------------------------------------------
+# `floorlog2(get_generalized_index(BeaconBlockBody, 'blob_kzg_commitments')) + 1 + ceillog2(MAX_BLOB_COMMITMENTS_PER_BLOCK)` = 7 + 1 + 12 = 20
+KZG_COMMITMENT_INCLUSION_PROOF_DEPTH_ELECTRA: 20
diff --git a/presets/minimal/electra.yaml b/presets/minimal/electra.yaml
@@ -43,3 +43,8 @@ MAX_WITHDRAWAL_REQUESTS_PER_PAYLOAD: 2
 # ---------------------------------------------------------------
 # 2**0 ( = 1) pending withdrawals
 MAX_PENDING_PARTIALS_PER_WITHDRAWALS_SWEEP: 1
+
+# Misc
+# ---------------------------------------------------------------
+# [customized] `floorlog2(get_generalized_index(BeaconBlockBody, 'blob_kzg_commitments')) + 1 + ceillog2(MAX_BLOB_COMMITMENTS_PER_BLOCK)` = 7 + 1 + 4 = 12
+KZG_COMMITMENT_INCLUSION_PROOF_DEPTH_ELECTRA: 12
diff --git a/pysetup/helpers.py b/pysetup/helpers.py
@@ -194,6 +194,10 @@ def dependency_order_class_objects(objects: Dict[str, str], custom_types: Dict[s
     for key, value in items:
         dependencies = []
         for line in value.split('\n'):
+            profile_match = re.match(r'class\s+\w+\s*\(Profile\[\s*(\w+)\s*\]\s*\)\s*:', line)
+            if profile_match is not None:
+                dependencies.append(profile_match.group(1))  # SSZ `Profile` base
+                continue
             if not re.match(r'\s+\w+: .+', line):
                 continue  # skip whitespace etc.
             line = line[line.index(':') + 1:]  # strip of field name

diff --git a/pysetup/spec_builders/deneb.py b/pysetup/spec_builders/deneb.py
@@ -72,10 +72,5 @@ def hardcoded_custom_type_dep_constants(cls, spec_object) -> Dict[str, str]:
             'FIELD_ELEMENTS_PER_BLOB': spec_object.preset_vars['FIELD_ELEMENTS_PER_BLOB'].value,
             'MAX_BLOBS_PER_BLOCK': spec_object.config_vars['MAX_BLOBS_PER_BLOCK'].value,
             'MAX_BLOB_COMMITMENTS_PER_BLOCK': spec_object.preset_vars['MAX_BLOB_COMMITMENTS_PER_BLOCK'].value,
-        }
-
-    @classmethod
-    def hardcoded_func_dep_presets(cls, spec_object) -> Dict[str, str]:
-        return {
             'KZG_COMMITMENT_INCLUSION_PROOF_DEPTH': spec_object.preset_vars['KZG_COMMITMENT_INCLUSION_PROOF_DEPTH'].value,
         }
diff --git a/pysetup/spec_builders/electra.py b/pysetup/spec_builders/electra.py
@@ -10,12 +10,20 @@ class ElectraSpecBuilder(BaseSpecBuilder):
     def imports(cls, preset_name: str):
         return f'''
 from eth2spec.deneb import {preset_name} as deneb
+from eth2spec.utils.ssz.ssz_typing import StableContainer, Profile
 '''
 
     @classmethod
     def hardcoded_ssz_dep_constants(cls) -> Dict[str, str]:
         return {
-            'FINALIZED_ROOT_GINDEX_ELECTRA': 'GeneralizedIndex(169)',
-            'CURRENT_SYNC_COMMITTEE_GINDEX_ELECTRA': 'GeneralizedIndex(86)',
-            'NEXT_SYNC_COMMITTEE_GINDEX_ELECTRA': 'GeneralizedIndex(87)',
+            'FINALIZED_ROOT_GINDEX_ELECTRA': 'GeneralizedIndex(553)',
+            'CURRENT_SYNC_COMMITTEE_GINDEX_ELECTRA': 'GeneralizedIndex(278)',
+            'NEXT_SYNC_COMMITTEE_GINDEX_ELECTRA': 'GeneralizedIndex(279)',
+            'EXECUTION_PAYLOAD_GINDEX_ELECTRA': 'GeneralizedIndex(137)',
+        }
+
+    @classmethod
+    def hardcoded_custom_type_dep_constants(cls, spec_object) -> Dict[str, str]:
+        return {
+            'KZG_COMMITMENT_INCLUSION_PROOF_DEPTH_ELECTRA': spec_object.preset_vars['KZG_COMMITMENT_INCLUSION_PROOF_DEPTH_ELECTRA'].value,
         }
diff --git a/setup.py b/setup.py
@@ -173,7 +173,7 @@ def _update_constant_vars_with_kzg_setups(constant_vars, preset_name):
     constant_vars['KZG_SETUP_G1_MONOMIAL'] = VariableDefinition(constant_vars['KZG_SETUP_G1_MONOMIAL'].value, str(kzg_setups[0]), comment, None)
     constant_vars['KZG_SETUP_G1_LAGRANGE'] = VariableDefinition(constant_vars['KZG_SETUP_G1_LAGRANGE'].value, str(kzg_setups[1]), comment, None)
     constant_vars['KZG_SETUP_G2_MONOMIAL'] = VariableDefinition(constant_vars['KZG_SETUP_G2_MONOMIAL'].value, str(kzg_setups[2]), comment, None)
-    
+
 
 def get_spec(file_name: Path, preset: Dict[str, str], config: Dict[str, str], preset_name=str) -> SpecObject:
     functions: Dict[str, str] = {}
@@ -227,7 +227,7 @@ def get_spec(file_name: Path, preset: Dict[str, str], config: Dict[str, str], pr
                     raise
 
                 if parent_class:
-                    assert parent_class == "Container"
+                    assert parent_class in ["Container", "StableContainer", "Profile"]
                 # NOTE: trim whitespace from spec
                 ssz_objects[current_name] = "\n".join(line.rstrip() for line in source.splitlines())
             else:
@@ -552,7 +552,7 @@ def run(self):
         "pycryptodome==3.15.0",
         "py_ecc==6.0.0",
         "milagro_bls_binding==1.9.0",
-        "remerkleable==0.1.28",
+        "remerkleable @ git+https://github.com/etan-status/remerkleable@dev/etan/sc-default",
         "trie==2.0.2",
         RUAMEL_YAML_VERSION,
         "lru-dict==1.2.0",

diff --git a/specs/capella/light-client/full-node.md b/specs/capella/light-client/full-node.md
@@ -47,7 +47,7 @@ def block_to_light_client_header(block: SignedBeaconBlock) -> LightClientHeader:
             withdrawals_root=hash_tree_root(payload.withdrawals),
         )
         execution_branch = ExecutionBranch(
-            compute_merkle_proof(block.message.body, EXECUTION_PAYLOAD_GINDEX))
+            compute_merkle_proof(block.message.body, execution_payload_gindex_at_slot(block.message.slot)))
     else:
         # Note that during fork transitions, `finalized_header` may still point to earlier forks.
         # While Bellatrix blocks also contain an `ExecutionPayload` (minus `withdrawals_root`),

diff --git a/specs/capella/light-client/sync-protocol.md b/specs/capella/light-client/sync-protocol.md
@@ -14,6 +14,7 @@
 - [Containers](#containers)
   - [Modified `LightClientHeader`](#modified-lightclientheader)
 - [Helper functions](#helper-functions)
+  - [`execution_payload_gindex_at_slot`](#execution_payload_gindex_at_slot)
   - [`get_lc_execution_root`](#get_lc_execution_root)
   - [Modified `is_valid_light_client_header`](#modified-is_valid_light_client_header)
 
@@ -55,6 +56,16 @@ class LightClientHeader(Container):
 
 ## Helper functions
 
+### `execution_payload_gindex_at_slot`
+
+```python
+def execution_payload_gindex_at_slot(slot: Slot) -> GeneralizedIndex:
+    epoch = compute_epoch_at_slot(slot)
+    assert epoch >= CAPELLA_FORK_EPOCH
+
+    return EXECUTION_PAYLOAD_GINDEX
+```
+
 ### `get_lc_execution_root`
 
 ```python
@@ -79,11 +90,10 @@ def is_valid_light_client_header(header: LightClientHeader) -> bool:
             and header.execution_branch == ExecutionBranch()
         )
 
-    return is_valid_merkle_branch(
+    return is_valid_normalized_merkle_branch(
         leaf=get_lc_execution_root(header),
         branch=header.execution_branch,
-        depth=floorlog2(EXECUTION_PAYLOAD_GINDEX),
-        index=get_subtree_index(EXECUTION_PAYLOAD_GINDEX),
+        gindex=execution_payload_gindex_at_slot(header.beacon.slot),
         root=header.beacon.body_root,
     )
 ```
diff --git a/specs/deneb/light-client/full-node.md b/specs/deneb/light-client/full-node.md
@@ -53,7 +53,7 @@ def block_to_light_client_header(block: SignedBeaconBlock) -> LightClientHeader:
             execution_header.excess_blob_gas = payload.excess_blob_gas
 
         execution_branch = ExecutionBranch(
-            compute_merkle_proof(block.message.body, EXECUTION_PAYLOAD_GINDEX))
+            compute_merkle_proof(block.message.body, execution_payload_gindex_at_slot(block.message.slot)))
     else:
         # Note that during fork transitions, `finalized_header` may still point to earlier forks.
         # While Bellatrix blocks also contain an `ExecutionPayload` (minus `withdrawals_root`),

diff --git a/specs/deneb/light-client/sync-protocol.md b/specs/deneb/light-client/sync-protocol.md
@@ -77,11 +77,10 @@ def is_valid_light_client_header(header: LightClientHeader) -> bool:
             and header.execution_branch == ExecutionBranch()
         )
 
-    return is_valid_merkle_branch(
+    return is_valid_normalized_merkle_branch(
         leaf=get_lc_execution_root(header),
         branch=header.execution_branch,
-        depth=floorlog2(EXECUTION_PAYLOAD_GINDEX),
-        index=get_subtree_index(EXECUTION_PAYLOAD_GINDEX),
+        gindex=execution_payload_gindex_at_slot(header.beacon.slot),
         root=header.beacon.body_root,
     )
 ```
diff --git a/specs/deneb/p2p-interface.md b/specs/deneb/p2p-interface.md
@@ -14,6 +14,7 @@ The specification of these changes continues in the same format as the network s
   - [Constant](#constant)
   - [Preset](#preset)
   - [Configuration](#configuration)
+  - [Custom types](#custom-types)
   - [Containers](#containers)
     - [`BlobSidecar`](#blobsidecar)
     - [`BlobIdentifier`](#blobidentifier)
@@ -66,6 +67,12 @@ The specification of these changes continues in the same format as the network s
 | `MIN_EPOCHS_FOR_BLOB_SIDECARS_REQUESTS`  | `2**12` (= 4096 epochs, ~18 days) | The minimum epoch range over which a node must serve blob sidecars  |
 | `BLOB_SIDECAR_SUBNET_COUNT`              | `6`                               | The number of blob sidecar subnets used in the gossipsub protocol.  |
 
+### Custom types
+
+| Name | SSZ equivalent | Description |
+| - | - | - |
+| `KZGCommitmentInclusionProof` | `Vector[Bytes32, KZG_COMMITMENT_INCLUSION_PROOF_DEPTH]` | Merkle branch of a single `blob_kzg_commitments` list item within `BeaconBlockBody` |
+
 ### Containers
 
 #### `BlobSidecar`
@@ -79,7 +86,7 @@ class BlobSidecar(Container):
     kzg_commitment: KZGCommitment
     kzg_proof: KZGProof  # Allows for quick verification of kzg_commitment
     signed_block_header: SignedBeaconBlockHeader
-    kzg_commitment_inclusion_proof: Vector[Bytes32, KZG_COMMITMENT_INCLUSION_PROOF_DEPTH]
+    kzg_commitment_inclusion_proof: KZGCommitmentInclusionProof
 ```
 
 #### `BlobIdentifier`
@@ -98,12 +105,12 @@ class BlobIdentifier(Container):
 
 ```python
 def verify_blob_sidecar_inclusion_proof(blob_sidecar: BlobSidecar) -> bool:
-    gindex = get_subtree_index(get_generalized_index(BeaconBlockBody, 'blob_kzg_commitments', blob_sidecar.index))
+    gindex = get_generalized_index(BeaconBlockBody, 'blob_kzg_commitments', blob_sidecar.index)
     return is_valid_merkle_branch(
         leaf=blob_sidecar.kzg_commitment.hash_tree_root(),
         branch=blob_sidecar.kzg_commitment_inclusion_proof,
-        depth=KZG_COMMITMENT_INCLUSION_PROOF_DEPTH,
-        index=gindex,
+        depth=floorlog2(gindex),
+        index=get_subtree_index(gindex),
         root=blob_sidecar.signed_block_header.message.body_root,
     )
 ```