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Some updates

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This commit is contained in:
Vitalik Buterin
2019-10-27 09:01:10 +08:00
committed by Danny Ryan
parent e5544d055b
commit 7fc2830730
1 changed files with 138 additions and 40 deletions
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specs/core/1_new_shards.md
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@@ -41,28 +41,61 @@ This document describes the shard transition function (data layer only) and the
| `ONLINE_PERIOD` | `2**3` (= 8) | epochs | ~51 min |
| `LIGHT_CLIENT_COMMITTEE_SIZE` | `2**7` (= 128) |
| `LIGHT_CLIENT_COMMITTEE_PERIOD` | `2**8` (= 256) | epochs | ~29 hours |
| `SHARD_STATE_ROOT_LENGTH` | `2**7` (= 128) | bytes |
| `MAX_SHARD_BLOCK
## Containers
### Aliases
| Name | Value |
| - | - |
| `SHARD_STATE_ROOT` | `BytesN[SHARD_STATE_ROOT_LENGTH]` |
### `AttestationData`
```python
class AttestationData(Container):
# Slot
slot: Slot
index: CommitteeIndex
# LMD GHOST vote
beacon_block_root: Hash
# FFG vote
source: Checkpoint
target: Checkpoint
# Shard data
shard_data: AttestationShardData
```
### `AttestationShardData`
```python
class AttestationShardData(Container):
# Shard block lengths
shard_block_lengths: List[uint8, MAX_CATCHUP_RATIO * MAX_SHARDS]
# Shard data roots
shard_data_roots: List[Hash, MAX_CATCHUP_RATIO * MAX_SHARDS]
# Intermediate state roots
shard_state_roots: List[Hash, MAX_CATCHUP_RATIO * MAX_SHARDS]
# Index
index: uint64
shard_state_roots: List[SHARD_STATE_ROOT, MAX_CATCHUP_RATIO * MAX_SHARDS]
```
### `ReducedAttestationData`
```python
class ReducedAttestationData(Container):
slot: Slot
index: CommitteeIndex
# LMD GHOST vote
beacon_block_root: Hash
# FFG vote
source: Checkpoint
target: Checkpoint
# Shard data root
shard_data_root: Hash
```
### `Attestation`
```python
@@ -73,6 +106,26 @@ class Attestation(Container):
signature: BLSSignature
```
### `ReducedAttestation`
```python
class ReducedAttestation(Container):
aggregation_bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]
data: ReducedAttestationData
custody_bits: List[Bitlist[MAX_VALIDATORS_PER_COMMITTEE], MAX_CATCHUP_RATIO * MAX_SHARDS]
signature: BLSSignature
```
### `IndexedAttestation`
```python
class IndexedAttestation(Container):
participants: List[ValidatorIndex, MAX_COMMITTEE_SIZE]
data: ReducedAttestationData
custody_bits: List[Bitlist[MAX_VALIDATORS_PER_COMMITTEE], MAX_CATCHUP_RATIO * MAX_SHARDS]
signature: BLSSignature
```
### `CompactCommittee`
```python
@@ -81,6 +134,15 @@ class CompactCommittee(Container):
compact_validators: List[uint64, MAX_VALIDATORS_PER_COMMITTEE]
```
### `AttestationCustodyBitWrapper`
```
class AttestationCustodyBitWrapper(Container):
attestation_root: Hash
index: uint64
bit: bool
```
## Helpers
### `get_online_validators`
@@ -103,16 +165,6 @@ def pack_compact_validator(index: int, slashed: bool, balance_in_increments: int
return (index << 16) + (slashed << 15) + balance_in_increments
```
### `unpack_compact_validator`
```python
def unpack_compact_validator(compact_validator: int) -> Tuple[int, bool, int]:
"""
Returns validator index, slashed, balance // EFFECTIVE_BALANCE_INCREMENT
"""
return compact_validator >> 16, bool((compact_validator >> 15) % 2), compact_validator & (2**15 - 1)
```
### `committee_to_compact_committee`
```python
@@ -129,6 +181,52 @@ def committee_to_compact_committee(state: BeaconState, committee: Sequence[Valid
return CompactCommittee(pubkeys=pubkeys, compact_validators=compact_validators)
```
### `get_light_client_committee`
```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)
return compute_committee(active_validator_indices, seed, 0, ACTIVE_SHARDS)[:TARGET_COMMITTEE_SIZE]
```
### `get_indexed_attestation`
```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)
```
### `is_valid_indexed_attestation`
``python
def is_valid_indexed_attestation(state: BeaconState, indexed_attestation: IndexedAttestation) -> bool:
"""
Check if ``indexed_attestation`` has valid indices and signature.
"""
# Verify indices are sorted
if indexed_attestation.participants != sorted(indexed_attestation.participants):
return False
# 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):
all_pubkeys.append(state.validators[participant].pubkey)
all_message_hashes.append(AttestationCustodyBitWrapper(hash_tree_root(indexed_attestation.data), i, bit))
return bls_verify_multiple(
pubkeys=all_pubkeys,
message_hashes=all_message_hashes,
signature=indexed_attestation.signature,
domain=get_domain(state, DOMAIN_BEACON_ATTESTER, indexed_attestation.data.target.epoch),
)
```
## Beacon Chain Changes
### New state variables
@@ -216,37 +314,37 @@ Check the length of attestations using `len(block.attestations) <= 4 * get_commi
### Light client processing
```python
signer_validators = []
signer_keys = []
for i, bit in enumerate(block.light_client_signature_bitfield):
if bit:
signer_keys.append(state.current_light_committee.pubkeys[i])
index, _, _ = unpack_compact_validator(state.current_light_committee.compact_validators[i])
signer_validators.append(index)
assert bls_verify(
pubkey=bls_aggregate_pubkeys(signer_keys),
message_hash=get_block_root_at_slot(state, state.slot - 1),
signature=block.light_client_signature,
domain=DOMAIN_LIGHT_CLIENT
)
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))
signer_validators = []
signer_keys = []
for i, bit in enumerate(block.light_client_signature_bitfield):
if bit:
signer_keys.append(state.validators[committee[i]].pubkey)
signer_validators.append(committee[i])
assert bls_verify(
pubkey=bls_aggregate_pubkeys(signer_keys),
message_hash=get_block_root_at_slot(state, state.slot - 1),
signature=block.light_client_signature,
domain=DOMAIN_LIGHT_CLIENT
)
```
### Epoch transition
```python
# Slowly remove validators from the "online" set if they do not show up
for index in range(len(state.validators)):
if state.online_countdown[index] != 0:
state.online_countdown[index] = state.online_countdown[index] - 1
# Update light client committees
if get_current_epoch(state) % LIGHT_CLIENT_COMMITTEE_PERIOD == 0:
state.current_light_committee = state.next_light_committee
seed = get_seed(state, get_current_epoch(state), DOMAIN_LIGHT_CLIENT)
active_indices = get_active_validator_indices(state, get_current_epoch(state))
committee = [active_indices[compute_shuffled_index(ValidatorIndex(i), len(active_indices), seed)] for i in range(LIGHT_CLIENT_COMMITTEE_SIZE)]
state.next_light_committee = committee_to_compact_committee(state, committee)
def phase_1_epoch_transition(state):
# Slowly remove validators from the "online" set if they do not show up
for index in range(len(state.validators)):
if state.online_countdown[index] != 0:
state.online_countdown[index] = state.online_countdown[index] - 1
# 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)))
```
### Fraud proofs