Merge branch 'dev' into eip-7495

ethereum · Jul 22, 2024 · 268166b · 268166b
2 parents d281ded + a42d670
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diff --git a/README.md b/README.md
@@ -26,7 +26,7 @@ Features are researched and developed in parallel, and then consolidated into se
 ### In-development Specifications
 | Code Name or Topic | Specs | Notes |
 | - | - | - |
-| Electra | <ul><li>Core</li><ul><li>[Beacon Chain changes](specs/electra/beacon-chain.md)</li><li>[EIP-6110 fork](specs/electra/fork.md)</li></ul><li>Additions</li><ul><li>[Honest validator guide changes](specs/electra/validator.md)</li></ul></ul> |
+| Electra | <ul><li>Core</li><ul><li>[Beacon Chain changes](specs/electra/beacon-chain.md)</li><li>[EIP-6110 fork](specs/electra/fork.md)</li></ul><li>Additions</li><ul><li>[Light client sync protocol changes](specs/electra/light-client/sync-protocol.md) ([fork](specs/electra/light-client/fork.md), [full node](specs/electra/light-client/full-node.md), [networking](specs/electra/light-client/p2p-interface.md))</li></ul><ul><li>[Honest validator guide changes](specs/electra/validator.md)</li></ul></ul> |
 | Sharding (outdated) | <ul><li>Core</li><ul><li>[Beacon Chain changes](specs/_features/sharding/beacon-chain.md)</li></ul><li>Additions</li><ul><li>[P2P networking](specs/_features/sharding/p2p-interface.md)</li></ul></ul> |
 | Custody Game (outdated) | <ul><li>Core</li><ul><li>[Beacon Chain changes](specs/_features/custody_game/beacon-chain.md)</li></ul><li>Additions</li><ul><li>[Honest validator guide changes](specs/_features/custody_game/validator.md)</li></ul></ul> | Dependent on sharding |
 | Data Availability Sampling (outdated) | <ul><li>Core</li><ul><li>[Core types and functions](specs/_features/das/das-core.md)</li><li>[Fork choice changes](specs/_features/das/fork-choice.md)</li></ul><li>Additions</li><ul><li>[P2P Networking](specs/_features/das/p2p-interface.md)</li><li>[Sampling process](specs/_features/das/sampling.md)</li></ul></ul> | <ul><li> Dependent on sharding</li><li>[Technical explainer](https://hackmd.io/@HWeNw8hNRimMm2m2GH56Cw/B1YJPGkpD)</li></ul> |

diff --git a/pysetup/spec_builders/electra.py b/pysetup/spec_builders/electra.py
@@ -12,12 +12,10 @@ def imports(cls, preset_name: str):
 from eth2spec.deneb import {preset_name} as deneb
 '''
 
-## TODO: deal with changed gindices
-
     @classmethod
     def hardcoded_ssz_dep_constants(cls) -> Dict[str, str]:
         return {
-            'FINALIZED_ROOT_GINDEX': 'GeneralizedIndex(169)',
-            'CURRENT_SYNC_COMMITTEE_GINDEX': 'GeneralizedIndex(86)',
-            'NEXT_SYNC_COMMITTEE_GINDEX': 'GeneralizedIndex(87)',
+            'FINALIZED_ROOT_GINDEX_ELECTRA': 'GeneralizedIndex(169)',
+            'CURRENT_SYNC_COMMITTEE_GINDEX_ELECTRA': 'GeneralizedIndex(86)',
+            'NEXT_SYNC_COMMITTEE_GINDEX_ELECTRA': 'GeneralizedIndex(87)',
         }
diff --git a/specs/_features/eip7594/polynomial-commitments-sampling.md b/specs/_features/eip7594/polynomial-commitments-sampling.md
@@ -39,12 +39,13 @@
     - [`coset_for_cell`](#coset_for_cell)
 - [Cells](#cells-1)
   - [Cell computation](#cell-computation)
+    - [`compute_cells_and_kzg_proofs_polynomialcoeff`](#compute_cells_and_kzg_proofs_polynomialcoeff)
     - [`compute_cells_and_kzg_proofs`](#compute_cells_and_kzg_proofs)
   - [Cell verification](#cell-verification)
     - [`verify_cell_kzg_proof_batch`](#verify_cell_kzg_proof_batch)
 - [Reconstruction](#reconstruction)
   - [`construct_vanishing_polynomial`](#construct_vanishing_polynomial)
-  - [`recover_data`](#recover_data)
+  - [`recover_polynomialcoeff`](#recover_polynomialcoeff)
   - [`recover_cells_and_kzg_proofs`](#recover_cells_and_kzg_proofs)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
@@ -555,6 +556,24 @@ def coset_for_cell(cell_index: CellIndex) -> Coset:
 
 ### Cell computation
 
+#### `compute_cells_and_kzg_proofs_polynomialcoeff`
+
+```python
+def compute_cells_and_kzg_proofs_polynomialcoeff(polynomial_coeff: PolynomialCoeff) -> Tuple[
+        Vector[Cell, CELLS_PER_EXT_BLOB],
+        Vector[KZGProof, CELLS_PER_EXT_BLOB]]:
+    """
+    Helper function which computes cells/proofs for a polynomial in coefficient form.
+    """
+    cells, proofs = [], []
+    for i in range(CELLS_PER_EXT_BLOB):
+        coset = coset_for_cell(CellIndex(i))
+        proof, ys = compute_kzg_proof_multi_impl(polynomial_coeff, coset)
+        cells.append(coset_evals_to_cell(ys))
+        proofs.append(proof)
+    return cells, proofs
+```
+
 #### `compute_cells_and_kzg_proofs`
 
 ```python
@@ -572,17 +591,7 @@ def compute_cells_and_kzg_proofs(blob: Blob) -> Tuple[
 
     polynomial = blob_to_polynomial(blob)
     polynomial_coeff = polynomial_eval_to_coeff(polynomial)
-
-    cells = []
-    proofs = []
-
-    for i in range(CELLS_PER_EXT_BLOB):
-        coset = coset_for_cell(CellIndex(i))
-        proof, ys = compute_kzg_proof_multi_impl(polynomial_coeff, coset)
-        cells.append(coset_evals_to_cell(ys))
-        proofs.append(proof)
-
-    return cells, proofs
+    return compute_cells_and_kzg_proofs_polynomialcoeff(polynomial_coeff)
 ```
 
 ### Cell verification
@@ -668,29 +677,27 @@ def construct_vanishing_polynomial(missing_cell_indices: Sequence[CellIndex]) ->
     return zero_poly_coeff
 ```
 
-### `recover_data`
+### `recover_polynomialcoeff`
 
 ```python
-def recover_data(cell_indices: Sequence[CellIndex],
-                 cells: Sequence[Cell],
-                 ) -> Sequence[BLSFieldElement]:
+def recover_polynomialcoeff(cell_indices: Sequence[CellIndex],
+                            cells: Sequence[Cell]) -> Sequence[BLSFieldElement]:
     """
-    Recover the missing evaluations for the extended blob, given at least half of the evaluations.
+    Recover the polynomial in coefficient form that when evaluated at the roots of unity will give the extended blob.
     """
-
-    # Get the extended domain. This will be referred to as the FFT domain.
+    # Get the extended domain. This will be referred to as the FFT domain
     roots_of_unity_extended = compute_roots_of_unity(FIELD_ELEMENTS_PER_EXT_BLOB)
 
-    # Flatten the cells into evaluations.
-    # If a cell is missing, then its evaluation is zero.
+    # Flatten the cells into evaluations
+    # If a cell is missing, then its evaluation is zero
     extended_evaluation_rbo = [0] * FIELD_ELEMENTS_PER_EXT_BLOB
     for cell_index, cell in zip(cell_indices, cells):
         start = cell_index * FIELD_ELEMENTS_PER_CELL
         end = (cell_index + 1) * FIELD_ELEMENTS_PER_CELL
         extended_evaluation_rbo[start:end] = cell
     extended_evaluation = bit_reversal_permutation(extended_evaluation_rbo)
 
-    # Compute Z(x) in monomial form
+    # Compute Z(x) in coefficient form
     # Z(x) is the polynomial which vanishes on all of the evaluations which are missing
     missing_cell_indices = [CellIndex(cell_index) for cell_index in range(CELLS_PER_EXT_BLOB)
                             if cell_index not in cell_indices]
@@ -703,7 +710,7 @@ def recover_data(cell_indices: Sequence[CellIndex],
     extended_evaluation_times_zero = [BLSFieldElement(int(a) * int(b) % BLS_MODULUS)
                                       for a, b in zip(zero_poly_eval, extended_evaluation)]
 
-    # Convert (E*Z)(x) to monomial form
+    # Convert (E*Z)(x) to coefficient form
     extended_evaluation_times_zero_coeffs = fft_field(extended_evaluation_times_zero, roots_of_unity_extended, inv=True)
 
     # Convert (E*Z)(x) to evaluation form over a coset of the FFT domain
@@ -713,18 +720,12 @@ def recover_data(cell_indices: Sequence[CellIndex],
     zero_poly_over_coset = coset_fft_field(zero_poly_coeff, roots_of_unity_extended)
 
     # Compute Q_3(x) = (E*Z)(x) / Z(x) in evaluation form over a coset of the FFT domain
-    reconstructed_poly_over_coset = [
-        div(a, b)
-        for a, b in zip(extended_evaluations_over_coset, zero_poly_over_coset)
-    ]
+    reconstructed_poly_over_coset = [div(a, b) for a, b in zip(extended_evaluations_over_coset, zero_poly_over_coset)]
 
-    # Convert Q_3(x) to monomial form
+    # Convert Q_3(x) to coefficient form
     reconstructed_poly_coeff = coset_fft_field(reconstructed_poly_over_coset, roots_of_unity_extended, inv=True)
 
-    # Convert Q_3(x) to evaluation form over the FFT domain and bit reverse the result
-    reconstructed_data = bit_reversal_permutation(fft_field(reconstructed_poly_coeff, roots_of_unity_extended))
-
-    return reconstructed_data
+    return reconstructed_poly_coeff[:FIELD_ELEMENTS_PER_BLOB]
 ```
 
 ### `recover_cells_and_kzg_proofs`
@@ -735,7 +736,7 @@ def recover_cells_and_kzg_proofs(cell_indices: Sequence[CellIndex],
         Vector[Cell, CELLS_PER_EXT_BLOB],
         Vector[KZGProof, CELLS_PER_EXT_BLOB]]:
     """
-    Given at least 50% of cells/proofs for a blob, recover all the cells/proofs.
+    Given at least 50% of cells for a blob, recover all the cells/proofs.
     This algorithm uses FFTs to recover cells faster than using Lagrange
     implementation, as can be seen here:
     https://ethresear.ch/t/reed-solomon-erasure-code-recovery-in-n-log-2-n-time-with-ffts/3039
@@ -745,6 +746,7 @@ def recover_cells_and_kzg_proofs(cell_indices: Sequence[CellIndex],
 
     Public method.
     """
+    # Check we have the same number of cells and indices
     assert len(cell_indices) == len(cells)
     # Check we have enough cells to be able to perform the reconstruction
     assert CELLS_PER_EXT_BLOB / 2 <= len(cell_indices) <= CELLS_PER_EXT_BLOB
@@ -757,29 +759,12 @@ def recover_cells_and_kzg_proofs(cell_indices: Sequence[CellIndex],
     for cell in cells:
         assert len(cell) == BYTES_PER_CELL
 
-    # Convert cells to coset evals
+    # Convert cells to coset evaluations
     cosets_evals = [cell_to_coset_evals(cell) for cell in cells]
 
-    reconstructed_data = recover_data(cell_indices, cosets_evals)
-
-    for cell_index, coset_evals in zip(cell_indices, cosets_evals):
-        start = cell_index * FIELD_ELEMENTS_PER_CELL
-        end = (cell_index + 1) * FIELD_ELEMENTS_PER_CELL
-        assert reconstructed_data[start:end] == coset_evals
-
-    recovered_cells = [
-        coset_evals_to_cell(reconstructed_data[i * FIELD_ELEMENTS_PER_CELL:(i + 1) * FIELD_ELEMENTS_PER_CELL])
-        for i in range(CELLS_PER_EXT_BLOB)]
-
-    polynomial_eval = reconstructed_data[:FIELD_ELEMENTS_PER_BLOB]
-    polynomial_coeff = polynomial_eval_to_coeff(polynomial_eval)
-    recovered_proofs = [None] * CELLS_PER_EXT_BLOB
-
-    for i in range(CELLS_PER_EXT_BLOB):
-        coset = coset_for_cell(CellIndex(i))
-        proof, ys = compute_kzg_proof_multi_impl(polynomial_coeff, coset)
-        assert coset_evals_to_cell(ys) == recovered_cells[i]
-        recovered_proofs[i] = proof
-
-    return recovered_cells, recovered_proofs
+    # Given the coset evaluations, recover the polynomial in coefficient form 
+    polynomial_coeff = recover_polynomialcoeff(cell_indices, cosets_evals)
+
+    # Recompute all cells/proofs
+    return compute_cells_and_kzg_proofs_polynomialcoeff(polynomial_coeff)
 ```
diff --git a/specs/altair/light-client/full-node.md b/specs/altair/light-client/full-node.md
@@ -76,7 +76,7 @@ def create_light_client_bootstrap(state: BeaconState,
         header=block_to_light_client_header(block),
         current_sync_committee=state.current_sync_committee,
         current_sync_committee_branch=CurrentSyncCommitteeBranch(
-            compute_merkle_proof(state, CURRENT_SYNC_COMMITTEE_GINDEX)),
+            compute_merkle_proof(state, current_sync_committee_gindex_at_slot(state.slot))),
     )
 ```
 
@@ -124,7 +124,7 @@ def create_light_client_update(state: BeaconState,
     if update_attested_period == update_signature_period:
         update.next_sync_committee = attested_state.next_sync_committee
         update.next_sync_committee_branch = NextSyncCommitteeBranch(
-            compute_merkle_proof(attested_state, NEXT_SYNC_COMMITTEE_GINDEX))
+            compute_merkle_proof(attested_state, next_sync_committee_gindex_at_slot(attested_state.slot)))
 
     # Indicate finality whenever possible
     if finalized_block is not None:
@@ -134,7 +134,7 @@ def create_light_client_update(state: BeaconState,
         else:
             assert attested_state.finalized_checkpoint.root == Bytes32()
         update.finality_branch = FinalityBranch(
-            compute_merkle_proof(attested_state, FINALIZED_ROOT_GINDEX))
+            compute_merkle_proof(attested_state, finalized_root_gindex_at_slot(attested_state.slot)))
 
     update.sync_aggregate = block.message.body.sync_aggregate
     update.signature_slot = block.message.slot

diff --git a/specs/altair/light-client/sync-protocol.md b/specs/altair/light-client/sync-protocol.md
@@ -21,13 +21,17 @@
   - [`LightClientOptimisticUpdate`](#lightclientoptimisticupdate)
   - [`LightClientStore`](#lightclientstore)
 - [Helper functions](#helper-functions)
+  - [`finalized_root_gindex_at_slot`](#finalized_root_gindex_at_slot)
+  - [`current_sync_committee_gindex_at_slot`](#current_sync_committee_gindex_at_slot)
+  - [`next_sync_committee_gindex_at_slot`](#next_sync_committee_gindex_at_slot)
   - [`is_valid_light_client_header`](#is_valid_light_client_header)
   - [`is_sync_committee_update`](#is_sync_committee_update)
   - [`is_finality_update`](#is_finality_update)
   - [`is_better_update`](#is_better_update)
   - [`is_next_sync_committee_known`](#is_next_sync_committee_known)
   - [`get_safety_threshold`](#get_safety_threshold)
   - [`get_subtree_index`](#get_subtree_index)
+  - [`is_valid_normalized_merkle_branch`](#is_valid_normalized_merkle_branch)
   - [`compute_sync_committee_period_at_slot`](#compute_sync_committee_period_at_slot)
 - [Light client initialization](#light-client-initialization)
   - [`initialize_light_client_store`](#initialize_light_client_store)
@@ -171,6 +175,30 @@ class LightClientStore(object):
 
 ## Helper functions
 
+### `finalized_root_gindex_at_slot`
+
+```python
+def finalized_root_gindex_at_slot(slot: Slot) -> GeneralizedIndex:
+    # pylint: disable=unused-argument
+    return FINALIZED_ROOT_GINDEX
+```
+
+### `current_sync_committee_gindex_at_slot`
+
+```python
+def current_sync_committee_gindex_at_slot(slot: Slot) -> GeneralizedIndex:
+    # pylint: disable=unused-argument
+    return CURRENT_SYNC_COMMITTEE_GINDEX
+```
+
+### `next_sync_committee_gindex_at_slot`
+
+```python
+def next_sync_committee_gindex_at_slot(slot: Slot) -> GeneralizedIndex:
+    # pylint: disable=unused-argument
+    return NEXT_SYNC_COMMITTEE_GINDEX
+```
+
 ### `is_valid_light_client_header`
 
 ```python
@@ -273,6 +301,22 @@ def get_subtree_index(generalized_index: GeneralizedIndex) -> uint64:
     return uint64(generalized_index % 2**(floorlog2(generalized_index)))
 ```
 
+### `is_valid_normalized_merkle_branch`
+
+```python
+def is_valid_normalized_merkle_branch(leaf: Bytes32,
+                                      branch: Sequence[Bytes32],
+                                      gindex: GeneralizedIndex,
+                                      root: Root) -> bool:
+    depth = floorlog2(gindex)
+    index = get_subtree_index(gindex)
+    num_extra = len(branch) - depth
+    for i in range(num_extra):
+        if branch[i] != Bytes32():
+            return False
+    return is_valid_merkle_branch(leaf, branch[num_extra:], depth, index, root)
+```
+
 ### `compute_sync_committee_period_at_slot`
 
 ```python
@@ -292,11 +336,10 @@ def initialize_light_client_store(trusted_block_root: Root,
     assert is_valid_light_client_header(bootstrap.header)
     assert hash_tree_root(bootstrap.header.beacon) == trusted_block_root
 
-    assert is_valid_merkle_branch(
+    assert is_valid_normalized_merkle_branch(
         leaf=hash_tree_root(bootstrap.current_sync_committee),
         branch=bootstrap.current_sync_committee_branch,
-        depth=floorlog2(CURRENT_SYNC_COMMITTEE_GINDEX),
-        index=get_subtree_index(CURRENT_SYNC_COMMITTEE_GINDEX),
+        gindex=current_sync_committee_gindex_at_slot(bootstrap.header.beacon.slot),
         root=bootstrap.header.beacon.state_root,
     )
 
@@ -364,11 +407,10 @@ def validate_light_client_update(store: LightClientStore,
         else:
             assert is_valid_light_client_header(update.finalized_header)
             finalized_root = hash_tree_root(update.finalized_header.beacon)
-        assert is_valid_merkle_branch(
+        assert is_valid_normalized_merkle_branch(
             leaf=finalized_root,
             branch=update.finality_branch,
-            depth=floorlog2(FINALIZED_ROOT_GINDEX),
-            index=get_subtree_index(FINALIZED_ROOT_GINDEX),
+            gindex=finalized_root_gindex_at_slot(update.attested_header.beacon.slot),
             root=update.attested_header.beacon.state_root,
         )
 
@@ -379,11 +421,10 @@ def validate_light_client_update(store: LightClientStore,
     else:
         if update_attested_period == store_period and is_next_sync_committee_known(store):
             assert update.next_sync_committee == store.next_sync_committee
-        assert is_valid_merkle_branch(
+        assert is_valid_normalized_merkle_branch(
             leaf=hash_tree_root(update.next_sync_committee),
             branch=update.next_sync_committee_branch,
-            depth=floorlog2(NEXT_SYNC_COMMITTEE_GINDEX),
-            index=get_subtree_index(NEXT_SYNC_COMMITTEE_GINDEX),
+            gindex=next_sync_committee_gindex_at_slot(update.attested_header.beacon.slot),
             root=update.attested_header.beacon.state_root,
         )
 

diff --git a/specs/capella/light-client/fork.md b/specs/capella/light-client/fork.md
@@ -7,8 +7,8 @@
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
 
 - [Introduction](#introduction)
-  - [Upgrading light client data](#upgrading-light-client-data)
-  - [Upgrading the store](#upgrading-the-store)
+- [Upgrading light client data](#upgrading-light-client-data)
+- [Upgrading the store](#upgrading-the-store)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 <!-- /TOC -->
@@ -17,7 +17,7 @@
 
 This document describes how to upgrade existing light client objects based on the [Altair specification](../../altair/light-client/sync-protocol.md) to Capella. This is necessary when processing pre-Capella data with a post-Capella `LightClientStore`. Note that the data being exchanged over the network protocols uses the original format.
 
-### Upgrading light client data
+## Upgrading light client data
 
 A Capella `LightClientStore` can still process earlier light client data. In order to do so, that pre-Capella data needs to be locally upgraded to Capella before processing.
 
@@ -70,7 +70,7 @@ def upgrade_lc_optimistic_update_to_capella(pre: bellatrix.LightClientOptimistic
     )
 ```
 
-### Upgrading the store
+## Upgrading the store
 
 Existing `LightClientStore` objects based on Altair MUST be upgraded to Capella before Capella based light client data can be processed. The `LightClientStore` upgrade MAY be performed before `CAPELLA_FORK_EPOCH`.