Use *new* optional_fast_aggregate_verify

ethereum · Nov 25, 2020 · f0864b8 · f0864b8
1 parent edee05c
commit f0864b8
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diff --git a/specs/lightclient/beacon-chain.md b/specs/lightclient/beacon-chain.md
@@ -49,6 +49,7 @@ This is a standalone beacon chain patch adding light client support via sync com
 | - | - | 
 | `SYNC_COMMITTEE_SIZE` | `uint64(2**10)` (= 1024) |
 | `SYNC_COMMITTEE_PUBKEY_AGGREGATES_SIZE` | `uint64(2**6)` (= 64) |
+| `G2_INFINITY_POINT_SIG` | `BLSSignature(b'\xc0' + b'\x00' * 95)` |
 
 ### Time parameters
 
@@ -96,6 +97,22 @@ class SyncCommittee(Container):
 
 ## Helper functions
 
+### `Predicates`
+
+#### `optional_fast_aggregate_verify`
+
+```python
+def optional_fast_aggregate_verify(pubkeys: Sequence[BLSPubkey], message: Bytes32, signature: BLSSignature) -> bool:
+    """
+    If ``pubkeys`` is an empty list, the given ``signature`` should be a stub ``G2_INFINITY_POINT_SIG``.
+    Otherwise, verify it with standard BLS FastAggregateVerify API.
+    """
+    if len(pubkeys) == 0:
+        return signature == G2_INFINITY_POINT_SIG
+    else:
+        return bls.FastAggregateVerify(pubkeys, message, signature)
+```
+
 ### Beacon state accessors
 
 #### `get_sync_committee_indices`
@@ -159,7 +176,7 @@ def process_sync_committee(state: BeaconState, body: BeaconBlockBody) -> None:
     participant_pubkeys = [state.validators[participant_index].pubkey for participant_index in participant_indices]
     domain = get_domain(state, DOMAIN_SYNC_COMMITTEE, compute_epoch_at_slot(previous_slot))
     signing_root = compute_signing_root(get_block_root_at_slot(state, previous_slot), domain)
-    assert bls.FastAggregateVerify(participant_pubkeys, signing_root, body.sync_committee_signature)
+    assert optional_fast_aggregate_verify(participant_pubkeys, signing_root, body.sync_committee_signature)
 
     # Reward sync committee participants
     participant_rewards = Gwei(0)

diff --git a/tests/core/pyspec/eth2spec/test/helpers/block.py b/tests/core/pyspec/eth2spec/test/helpers/block.py
@@ -1,3 +1,4 @@
+from eth2spec.test.context import LIGHTCLIENT
 from eth2spec.test.helpers.keys import privkeys
 from eth2spec.utils import bls
 from eth2spec.utils.bls import only_with_bls
@@ -89,6 +90,10 @@ def build_empty_block(spec, state, slot=None):
     empty_block.proposer_index = spec.get_beacon_proposer_index(state)
     empty_block.body.eth1_data.deposit_count = state.eth1_deposit_index
     empty_block.parent_root = parent_block_root
+
+    if spec.fork == LIGHTCLIENT:
+        empty_block.body.sync_committee_signature = spec.G2_INFINITY_POINT_SIG
+
     apply_randao_reveal(spec, state, empty_block)
     return empty_block