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Vitalik Buterin 2019-11-01 07:58:13 -07:00 committed by Danny Ryan
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specs/core/1_new_shards.md
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@ -29,8 +29,8 @@
- [`get_indexed_attestation`](#get_indexed_attestation)
- [`is_valid_indexed_attestation`](#is_valid_indexed_attestation)
- [Beacon Chain Changes](#beacon-chain-changes)
- [New state variables](#new-state-variables)
- [New block data structures](#new-block-data-structures)
- [New beacon state fields](#new-beacon-state-fields)
- [New beacon block data fields](#new-beacon-block-data-fields)
- [Attestation processing](#attestation-processing)
- [Light client processing](#light-client-processing)
- [Epoch transition](#epoch-transition)
@ -63,6 +63,7 @@ This document describes the shard transition function (data layer only) and the
| `EMPTY_CHUNK_ROOT` | `hash_tree_root(BytesN[SHARD_BLOCK_CHUNK_SIZE]())` | |
| `MAX_GASPRICE` | `2**14` (= 16,384) | Gwei | |
| `GASPRICE_ADJUSTMENT_COEFFICIENT` | `2**3` (= 8) | |
| `DOMAIN_SHARD_LIGHT_CLIENT` | `192` | |
## Containers
@ -87,8 +88,8 @@ class AttestationData(Container):
# FFG vote
source: Checkpoint
target: Checkpoint
# Shard transition hash
shard_transition_hash: Hash
# Shard transition root
shard_transition_root: Hash
```
### `ShardTransition`
@ -98,9 +99,9 @@ class ShardTransition(Container):
# Starting from slot
start_slot: Slot
# Shard block lengths
shard_block_lengths: List[uint8, MAX_SHARD_BLOCKS_PER_ATTESTATION]
shard_block_lengths: List[uint64, MAX_SHARD_BLOCKS_PER_ATTESTATION]
# Shard data roots
shard_data_roots: List[Hash, List[Hash, MAX_SHARD_BLOCK_CHUNKS], MAX_SHARD_BLOCKS_PER_ATTESTATION]
shard_data_roots: List[List[Hash, MAX_SHARD_BLOCK_CHUNKS], MAX_SHARD_BLOCKS_PER_ATTESTATION]
# Intermediate state roots
shard_state_roots: List[ShardState, MAX_SHARD_BLOCKS_PER_ATTESTATION]
```
@ -119,7 +120,7 @@ class Attestation(Container):
```python
class IndexedAttestation(Container):
participants: List[ValidatorIndex, MAX_COMMITTEE_SIZE]
participants: List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE]
data: AttestationData
custody_bits: List[Bitlist[MAX_VALIDATORS_PER_COMMITTEE], MAX_SHARD_BLOCKS_PER_ATTESTATION]
signature: BLSSignature
@ -138,10 +139,21 @@ class CompactCommittee(Container):
```python
class AttestationCustodyBitWrapper(Container):
attestation_root: Hash
index: uint64
block_index: uint64
bit: bool
```
### `PendingAttestation`
```python
class PendingAttestation(Container):
aggregation_bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]
data: AttestationData
inclusion_delay: Slot
proposer_index: ValidatorIndex
crosslink_success: bool
```
## Helpers
### `get_online_validators`
@ -184,9 +196,11 @@ def committee_to_compact_committee(state: BeaconState, committee: Sequence[Valid
```python
def get_light_client_committee(beacon_state: BeaconState, epoch: Epoch) -> Sequence[ValidatorIndex]:
assert epoch % LIGHT_CLIENT_COMMITTEE_PERIOD == 0
active_validator_indices = get_active_validator_indices(beacon_state, epoch)
seed = get_seed(beacon_state, epoch, DOMAIN_SHARD_LIGHT_CLIENT)
source_epoch = epoch - epoch % LIGHT_CLIENT_COMMITTEE_PERIOD
if source_epoch > 0:
source_epoch -= LIGHT_CLIENT_COMMITTEE_PERIOD
active_validator_indices = get_active_validator_indices(beacon_state, source_epoch)
seed = get_seed(beacon_state, source_epoch, DOMAIN_SHARD_LIGHT_CLIENT)
return compute_committee(active_validator_indices, seed, 0, ACTIVE_SHARDS)[:TARGET_COMMITTEE_SIZE]
```
@ -195,7 +209,7 @@ def get_light_client_committee(beacon_state: BeaconState, epoch: Epoch) -> Seque
```python
def get_indexed_attestation(beacon_state: BeaconState, attestation: Attestation) -> IndexedAttestation:
attesting_indices = get_attesting_indices(state, attestation.data, attestation.aggregation_bits)
return IndexedAttestation(attesting_indices, data, custody_bits, signature)
return IndexedAttestation(attesting_indices, attestation.data, attestation.custody_bits, attestation.signature)
```
### `update_gasprice`
@ -228,8 +242,8 @@ def is_valid_indexed_attestation(state: BeaconState, indexed_attestation: Indexe
# Verify aggregate signature
all_pubkeys = []
all_message_hashes = []
for participant, custody_bits in zip(participants, indexed_attestation.custody_bits):
for i, bit in enumerate(custody_bits):
for i, custody_bits in enumerate(indexed_attestation.custody_bits):
for participant, bit in zip(participants, custody_bits):
all_pubkeys.append(state.validators[participant].pubkey)
# Note: only 2N distinct message hashes
all_message_hashes.append(AttestationCustodyBitWrapper(hash_tree_root(indexed_attestation.data), i, bit))
@ -244,7 +258,7 @@ def is_valid_indexed_attestation(state: BeaconState, indexed_attestation: Indexe
## Beacon Chain Changes
### New state variables
### New beacon state fields
```python
shard_states: Vector[ShardState, MAX_SHARDS]
@ -253,7 +267,7 @@ def is_valid_indexed_attestation(state: BeaconState, indexed_attestation: Indexe
next_light_committee: CompactCommittee
```
### New block data structures
### New beacon block data fields
```python
shard_transitions: Vector[ShardTransition, MAX_SHARDS]
@ -268,10 +282,10 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
data = attestation.data
assert data.index < ACTIVE_SHARDS
shard = (data.index + get_start_shard(state, data.slot)) % ACTIVE_SHARDS
proposer_index=get_beacon_proposer_index(state)
proposer_index = get_beacon_proposer_index(state)
# Signature check
committee = get_crosslink_committee(state, get_current_epoch(state), shard)
committee = get_beacon_committee(state, get_current_epoch(state), shard)
for bits in attestation.custody_bits + [attestation.aggregation_bits]:
assert len(bits) == len(committee)
# Check signature
@ -281,8 +295,6 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
# Prepare pending attestation object
pending_attestation = PendingAttestation(
slot=data.slot,
shard=shard,
aggregation_bits=attestation.aggregation_bits,
inclusion_delay=state.slot - data.slot,
crosslink_success=False,
@ -305,7 +317,7 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
if get_total_balance(state, online_indices.intersection(attesting_indices)) * 3 >= get_total_balance(state, online_indices) * 2:
# Check correct formatting of shard transition data
transition = block.shard_transitions[shard]
assert data.shard_transition_hash == hash_tree_root(transition)
assert data.shard_transition_root == hash_tree_root(transition)
assert len(transition.shard_data_roots) == len(transition.shard_states) == len(transition.shard_block_lengths) == len(offset_slots)
assert transition.start_slot == start_slot
@ -331,13 +343,13 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
# Apply proposer reward and cost
estimated_attester_reward = sum([get_base_reward(state, attester) for attester in attesting_indices])
increase_balance(state, proposer, estimated_attester_reward // PROPOSER_REWARD_COEFFICIENT)
for state, length in zip(transition.shard_states, transition.shard_block_lengths):
decrease_balance(state, proposer, state.gasprice * length)
for shard_state, slot, length in zip(transition.shard_states, offset_slots, transition.shard_block_lengths):
decrease_balance(state, get_shard_proposer(state, shard, slot), shard_state.gasprice * length)
# Type 2: delayed attestations
else:
assert slot_to_epoch(data.slot) in (get_current_epoch(state), get_previous_epoch(state))
assert data.shard_transition_hash == Hash()
assert state.slot - slot_to_epoch(data.slot) < EPOCH_LENGTH
assert data.shard_transition_root == Hash()
assert len(attestation.custody_bits) == 0
for index in attesting_indices:
@ -365,14 +377,18 @@ def misc_block_post_process(state: BeaconState, block: BeaconBlock):
### Light client processing
```python
def verify_light_client_signatures(state: BeaconState, block: BeaconBlock):
period_start = get_current_epoch(state) - get_current_epoch(state) % LIGHT_CLIENT_COMMITTEE_PERIOD
committee = get_light_client_committee(state, period_start - min(period_start, LIGHT_CLIENT_COMMITTEE_PERIOD))
def process_light_client_signatures(state: BeaconState, block: BeaconBlock):
committee = get_light_client_committee(state, get_current_epoch(state))
assert len(block.light_client_signature_bitfield) == len(committee)
tot_reward = 0
signer_keys = []
for i, bit in enumerate(block.light_client_signature_bitfield):
if bit:
signer_keys.append(state.validators[committee[i]].pubkey)
increase_balance(state, committee[i], get_base_reward(state, committee[i]))
tot_reward += get_base_reward(state, committee[i])
increase_balance(state, get_beacon_proposer_index(state), tot_reward // PROPOSER_REWARD_COEFFICIENT)
assert bls_verify(
pubkey=bls_aggregate_pubkeys(signer_keys),
@ -394,7 +410,8 @@ def phase_1_epoch_transition(state):
# Update light client committees
if get_current_epoch(state) % LIGHT_CLIENT_COMMITTEE_PERIOD == 0:
state.current_light_committee = state.next_light_committee
state.next_light_committee = committee_to_compact_committee(state, get_light_client_committee(state, get_current_epoch(state)))
new_committee = get_light_client_committee(state, get_current_epoch(state) + LIGHT_CLIENT_COMMITTEE_PERIOD)
state.next_light_committee = committee_to_compact_committee(state, new_committee)
```
### Fraud proofs
@ -420,7 +437,7 @@ def shard_state_transition(shard: Shard, slot: Slot, pre_state: Hash, previous_b
domain=DOMAIN_SHARD_PROPOSER
)
# We will add something more substantive in phase 2
length = len(block.data.rstrip(b'\x00'))
length = len(block_data.rstrip(b'\x00'))
return ShardState(slot=slot, root=hash(pre_state + hash_tree_root(block_data)), gasprice=update_gasprice(pre_state, length), latest_block_hash = hash(block_data))
```