Merge pull request #522 from ethereum/JustinDrake-patch-1

Attester slashing fixes

specs/core/0_beacon-chain.md

@@ -26,7 +26,7 @@
                 - [`ProposerSlashing`](#proposerslashing)
             - [Attester slashings](#attester-slashings)
                 - [`AttesterSlashing`](#attesterslashing)
-                - [`SlashableVote`](#slashablevote)
+                - [`SlashableAttestation`](#slashableattestation)
             - [Attestations](#attestations)
                 - [`Attestation`](#attestation)
                 - [`AttestationData`](#attestationdata)
@@ -78,7 +78,7 @@
         - [`get_domain`](#get_domain)
         - [`get_bitfield_bit`](#get_bitfield_bit)
         - [`verify_bitfield`](#verify_bitfield)
-        - [`verify_slashable_vote`](#verify_slashable_vote)
+        - [`verify_slashable_attestation`](#verify_slashable_attestation)
         - [`is_double_vote`](#is_double_vote)
         - [`is_surround_vote`](#is_surround_vote)
         - [`integer_squareroot`](#integer_squareroot)
@@ -298,23 +298,23 @@ The following data structures are defined as [SimpleSerialize (SSZ)](https://git
 
 ```python
 {
-    # First batch of votes
+    # First slashable attestation
-    'slashable_vote_1': SlashableVote,
+    'slashable_attestation_1': SlashableAttestation,
-    # Second batch of votes
+    # Second slashable attestation
-    'slashable_vote_2': SlashableVote,
+    'slashable_attestation_2': SlashableAttestation,
 }
 ```
 
-##### `SlashableVote`
+##### `SlashableAttestation`
 
 ```python
 {
     # Validator indices
     'validator_indices': '[uint64]',
-    # Custody bitfield
-    'custody_bitfield': 'bytes',
     # Attestation data
     'data': AttestationData,
+    # Custody bitfield
+    'custody_bitfield': 'bytes',
     # Aggregate signature
     'aggregate_signature': 'bytes96',
 }
@@ -326,10 +326,10 @@ The following data structures are defined as [SimpleSerialize (SSZ)](https://git
 
 ```python
 {
-    # Attestation data
-    'data': AttestationData,
     # Attester aggregation bitfield
     'aggregation_bitfield': 'bytes',
+    # Attestation data
+    'data': AttestationData,
     # Custody bitfield
     'custody_bitfield': 'bytes',
     # BLS aggregate signature
@@ -552,14 +552,14 @@ The following data structures are defined as [SimpleSerialize (SSZ)](https://git
 
 ```python
 {
-    # Signed data
-    'data': AttestationData,
     # Attester aggregation bitfield
     'aggregation_bitfield': 'bytes',
+    # Attestation data
+    'data': AttestationData,
     # Custody bitfield
     'custody_bitfield': 'bytes',
-    # Slot the attestation was included
+    # Inclusion slot
-    'slot_included': 'uint64',
+    'inclusion_slot': 'uint64',
 }
 ```
 
@@ -1012,33 +1012,33 @@ def verify_bitfield(bitfield: bytes, committee_size: int) -> bool:
     return True
 ```
 
-### `verify_slashable_vote`
+### `verify_slashable_attestation`
 
 ```python
-def verify_slashable_vote(state: BeaconState, slashable_vote: SlashableVote) -> bool:
+def verify_slashable_attestation(state: BeaconState, slashable_attestation: SlashableAttestation) -> bool:
     """
-    Verify validity of ``slashable_vote`` fields.
+    Verify validity of ``slashable_attestation`` fields.
     """
-    if slashable_vote.custody_bitfield != b'\x00' * len(slashable_vote.custody_bitfield):  # [TO BE REMOVED IN PHASE 1]
+    if slashable_attestation.custody_bitfield != b'\x00' * len(slashable_attestation.custody_bitfield):  # [TO BE REMOVED IN PHASE 1]
         return False
 
-    if len(slashable_vote.validator_indices) == 0:
+    if len(slashable_attestation.validator_indices) == 0:
         return False
 
-    for i in range(len(slashable_vote.validator_indices) - 1):
+    for i in range(len(slashable_attestation.validator_indices) - 1):
-        if slashable_vote.validator_indices[i] >= slashable_vote.validator_indices[i + 1]:
+        if slashable_attestation.validator_indices[i] >= slashable_attestation.validator_indices[i + 1]:
             return False
 
-    if not verify_bitfield(slashable_vote.custody_bitfield, len(slashable_vote.validator_indices)):
+    if not verify_bitfield(slashable_attestation.custody_bitfield, len(slashable_attestation.validator_indices)):
         return False
 
-    if len(slashable_vote.validator_indices) > MAX_INDICES_PER_SLASHABLE_VOTE:
+    if len(slashable_attestation.validator_indices) > MAX_INDICES_PER_SLASHABLE_VOTE:
         return False
 
     custody_bit_0_indices = []
     custody_bit_1_indices = []
-    for i, validator_index in enumerate(slashable_vote.validator_indices):
+    for i, validator_index in enumerate(slashable_attestation.validator_indices):
-        if get_bitfield_bit(slashable_vote.custody_bitfield, i) == 0b0:
+        if get_bitfield_bit(slashable_attestation.custody_bitfield, i) == 0b0:
             custody_bit_0_indices.append(validator_index)
         else:
             custody_bit_1_indices.append(validator_index)
@@ -1049,10 +1049,10 @@ def verify_slashable_vote(state: BeaconState, slashable_vote: SlashableVote) ->
             bls_aggregate_pubkeys([state.validator_registry[i].pubkey for i in custody_bit_1_indices]),
         ],
         messages=[
-            hash_tree_root(AttestationDataAndCustodyBit(attestation_data=slashable_vote.data, custody_bit=0b0)),
+            hash_tree_root(AttestationDataAndCustodyBit(attestation_data=slashable_attestation.data, custody_bit=0b0)),
-            hash_tree_root(AttestationDataAndCustodyBit(attestation_data=slashable_vote.data, custody_bit=0b1)),
+            hash_tree_root(AttestationDataAndCustodyBit(attestation_data=slashable_attestation.data, custody_bit=0b1)),
         ],
-        signature=slashable_vote.aggregate_signature,
+        signature=slashable_attestation.aggregate_signature,
         domain=get_domain(
             state.fork,
             slot_to_epoch(vote_data.data.slot),
@@ -1067,9 +1067,7 @@ def verify_slashable_vote(state: BeaconState, slashable_vote: SlashableVote) ->
 def is_double_vote(attestation_data_1: AttestationData,
                    attestation_data_2: AttestationData) -> bool
     """
-    Assumes ``attestation_data_1`` is distinct from ``attestation_data_2``.
+    Checks if the two ``AttestationData`` have the same target.
-    Returns True if the provided ``AttestationData`` are slashable
-    due to a 'double vote'.
     """
     target_epoch_1 = slot_to_epoch(attestation_data_1.slot)
     target_epoch_2 = slot_to_epoch(attestation_data_2.slot)
@@ -1082,11 +1080,7 @@ def is_double_vote(attestation_data_1: AttestationData,
 def is_surround_vote(attestation_data_1: AttestationData,
                      attestation_data_2: AttestationData) -> bool:
     """
-    Assumes ``attestation_data_1`` is distinct from ``attestation_data_2``.
+    Checks if ``attestation_data_1`` surrounds ``attestation_data_2``.
-    Returns True if the provided ``AttestationData`` are slashable
-    due to a 'surround vote'.
-    Note: parameter order matters as this function only checks
-    that ``attestation_data_1`` surrounds ``attestation_data_2``.
     """
     source_epoch_1 = attestation_data_1.justified_epoch
     source_epoch_2 = attestation_data_2.justified_epoch
@@ -1598,15 +1592,15 @@ Verify that `len(block.body.attester_slashings) <= MAX_ATTESTER_SLASHINGS`.
 
 For each `attester_slashing` in `block.body.attester_slashings`:
 
-* Let `slashable_vote_1 = attester_slashing.slashable_vote_1`.
+* Let `slashable_attestation_1 = attester_slashing.slashable_attestation_1`.
-* Let `slashable_vote_2 = attester_slashing.slashable_vote_2`.
+* Let `slashable_attestation_2 = attester_slashing.slashable_attestation_2`.
-* Let `intersection = [x for x in slashable_vote_1.validator_indices if x in slashable_vote_2.validator_indices]`.
+* Verify that `slashable_attestation_1.data != slashable_attestation_2.data`.
-* Verify that `len(intersection) >= 1`.
+* Verify that `is_double_vote(slashable_attestation_1.data, slashable_attestation_2.data)` or `is_surround_vote(slashable_attestation_1.data, slashable_attestation_2.data)`.
-* Verify that `slashable_vote_1.data != slashable_vote_2.data`.
+* Verify that `verify_slashable_attestation(state, slashable_attestation_1)`.
-* Verify that `is_double_vote(slashable_vote_1.data, slashable_vote_2.data)` or `is_surround_vote(slashable_vote_1.data, slashable_vote_2.data)`.
+* Verify that `verify_slashable_attestation(state, slashable_attestation_2)`.
-* Verify that `verify_slashable_vote(state, slashable_vote_1)`.
+* Let `slashable_indices = [index for index in slashable_attestation_1.validator_indices if index in slashable_attestation_2.validator_indices and state.validator_registry[index].penalized_epoch > get_current_epoch(state)]`.
-* Verify that `verify_slashable_vote(state, slashable_vote_2)`.
+* Verify that `len(slashable_indices) >= 1`.
-* For each [validator](#dfn-validator) index `i` in `intersection` run `penalize_validator(state, i)` if `state.validator_registry[i].penalized_epoch > get_current_epoch(state)`.
+* Run `penalize_validator(state, index)` for each `index` in `slashable_indices`.
 
 ##### Attestations
 
@@ -1647,7 +1641,7 @@ For each `attestation` in `block.body.attestations`:
 ```
 
 * [TO BE REMOVED IN PHASE 1] Verify that `attestation.data.shard_block_root == ZERO_HASH`.
-* Append `PendingAttestation(data=attestation.data, aggregation_bitfield=attestation.aggregation_bitfield, custody_bitfield=attestation.custody_bitfield, slot_included=state.slot)` to `state.latest_attestations`.
+* Append `PendingAttestation(data=attestation.data, aggregation_bitfield=attestation.aggregation_bitfield, custody_bitfield=attestation.custody_bitfield, inclusion_slot=state.slot)` to `state.latest_attestations`.
 
 ##### Deposits
 
@@ -1748,8 +1742,8 @@ For every `slot in range(get_epoch_start_slot(previous_epoch), get_epoch_start_s
 
 Define the following helpers to process attestation inclusion rewards and inclusion distance reward/penalty. For every attestation `a` in `previous_epoch_attestations`:
 
-* Let `inclusion_slot(state, index) = a.slot_included` for the attestation `a` where `index` is in `get_attestation_participants(state, a.data, a.aggregation_bitfield)`. If multiple attestations are applicable, the attestation with lowest `slot_included` is considered.
+* Let `inclusion_slot(state, index) = a.inclusion_slot` for the attestation `a` where `index` is in `get_attestation_participants(state, a.data, a.aggregation_bitfield)`. If multiple attestations are applicable, the attestation with lowest `inclusion_slot` is considered.
-* Let `inclusion_distance(state, index) = a.slot_included - a.data.slot` where `a` is the above attestation.
+* Let `inclusion_distance(state, index) = a.inclusion_slot - a.data.slot` where `a` is the above attestation.
 
 #### Eth1 data