219 lines
8.0 KiB
Markdown
219 lines
8.0 KiB
Markdown
# Phase 1 miscellaneous beacon chain changes
|
|
|
|
## Table of contents
|
|
|
|
<!-- TOC -->
|
|
|
|
- [Phase 1 miscellaneous beacon chain changes](#phase-1-miscellaneous-beacon-chain-changes)
|
|
- [Table of contents](#table-of-contents)
|
|
- [Classes](#classes)
|
|
- [CompactCommittee](#compactcommittee)
|
|
- [ShardReceiptProof](#shardreceiptproof)
|
|
- [Helpers](#helpers)
|
|
- [pack_compact_validator](#pack_compact_validator)
|
|
- [unpack_compact_validator](#unpack_compact_validator)
|
|
- [committee_to_compact_committee](#committee_to_compact_committee)
|
|
- [get_previous_power_of_2](#get_previous_power_of_2)
|
|
- [verify_merkle_proof](#verify_merkle_proof)
|
|
- [concat_generalized_indices](#concat_generalized_indices)
|
|
- [compute_historical_state_generalized_index](#compute_historical_state_generalized_index)
|
|
- [get_generalized_index_of_crosslink_header](#get_generalized_index_of_crosslink_header)
|
|
- [process_shard_receipt](#process_shard_receipt)
|
|
- [Changes](#changes)
|
|
- [Persistent committees](#persistent-committees)
|
|
- [Shard receipt processing](#shard-receipt-processing)
|
|
|
|
<!-- /TOC -->
|
|
|
|
## Classes
|
|
|
|
#### `CompactCommittee`
|
|
|
|
```python
|
|
class CompactCommittee(Container):
|
|
pubkeys: List[BLSPubkey, MAX_VALIDATORS_PER_COMMITTEE]
|
|
compact_validators: List[uint64, MAX_VALIDATORS_PER_COMMITTEE]
|
|
```
|
|
|
|
#### `ShardReceiptProof`
|
|
|
|
```python
|
|
class ShardReceiptProof(Container):
|
|
shard: Shard
|
|
proof: List[Hash, PLACEHOLDER]
|
|
receipt: List[ShardReceiptDelta, PLACEHOLDER]
|
|
```
|
|
|
|
## Helpers
|
|
|
|
#### `pack_compact_validator`
|
|
|
|
```python
|
|
def pack_compact_validator(index: int, slashed: bool, balance_in_increments: int) -> int:
|
|
"""
|
|
Creates a compact validator object representing index, slashed status, and compressed balance.
|
|
Takes as input balance-in-increments (// EFFECTIVE_BALANCE_INCREMENT) to preserve symmetry with
|
|
the unpacking function.
|
|
"""
|
|
return (index << 16) + (slashed << 15) + balance_in_increments
|
|
```
|
|
|
|
#### `unpack_compact_validator`
|
|
|
|
```python
|
|
def unpack_compact_validator(compact_validator: uint64) -> Tuple[uint64, bool, uint64]:
|
|
"""
|
|
Returns validator index, slashed, balance // EFFECTIVE_BALANCE_INCREMENT
|
|
"""
|
|
return compact_validator >> 16, (compact_validator >> 15) % 2, compact_validator & (2**15 - 1)
|
|
```
|
|
|
|
#### `committee_to_compact_committee`
|
|
|
|
```python
|
|
def committee_to_compact_committee(state: BeaconState, committee: Sequence[ValidatorIndex]) -> CompactCommittee:
|
|
"""
|
|
Given a state and a list of validator indices, outputs the CompactCommittee representing them.
|
|
"""
|
|
validators = [state.validators[i] for i in committee]
|
|
compact_validators = [
|
|
pack_compact_validator(i, v.slashed, v.effective_balance // EFFECTIVE_BALANCE_INCREMENT)
|
|
for i, v in zip(committee, validators)
|
|
]
|
|
pubkeys = [v.pubkey for v in validators]
|
|
return CompactCommittee(pubkeys=pubkeys, compact_validators=compact_validators)
|
|
```
|
|
|
|
#### `get_previous_power_of_2`
|
|
|
|
```python
|
|
def get_previous_power_of_2(x: int) -> int:
|
|
return x if x <= 2 else 2 * get_previous_power_of_2(x // 2)
|
|
```
|
|
|
|
#### `verify_merkle_proof`
|
|
|
|
```python
|
|
def verify_merkle_proof(leaf: Hash, proof: Sequence[Hash], index: GeneralizedIndex, root: Hash) -> bool:
|
|
assert len(proof) == get_generalized_index_length(index)
|
|
for i, h in enumerate(proof):
|
|
if get_generalized_index_bit(index, i):
|
|
leaf = hash(h + leaf)
|
|
else:
|
|
leaf = hash(leaf + h)
|
|
return leaf == root
|
|
```
|
|
|
|
#### `compute_historical_state_generalized_index`
|
|
|
|
```python
|
|
def compute_historical_state_generalized_index(earlier: ShardSlot, later: ShardSlot) -> GeneralizedIndex:
|
|
"""
|
|
Computes the generalized index of the state root of slot `frm` based on the state root of slot `to`.
|
|
Relies on the `history_acc` in the `ShardState`, where `history_acc[i]` maintains the most recent 2**i'th
|
|
slot state. Works by tracing a `log(later-earlier)` step path from `later` to `earlier` through intermediate
|
|
blocks at the next available multiples of descending powers of two.
|
|
"""
|
|
o = GeneralizedIndex(1)
|
|
for i in range(63, -1, -1):
|
|
if (later - 1) & 2**i > (earlier - 1) & 2**i:
|
|
later = later - ((later - 1) % 2**i) - 1
|
|
o = concat_generalized_indices(o, get_generalized_index(ShardState, 'history_acc', i))
|
|
return o
|
|
```
|
|
|
|
#### `get_generalized_index_of_crosslink_header`
|
|
|
|
```python
|
|
def get_generalized_index_of_crosslink_header(index: int) -> GeneralizedIndex:
|
|
"""
|
|
Gets the generalized index for the root of the index'th header in a crosslink.
|
|
"""
|
|
MAX_CROSSLINK_SIZE = SHARD_BLOCK_SIZE_LIMIT * SHARD_SLOTS_PER_BEACON_SLOT * SLOTS_PER_EPOCH * MAX_EPOCHS_PER_CROSSLINK
|
|
assert MAX_CROSSLINK_SIZE == get_previous_power_of_2(MAX_CROSSLINK_SIZE)
|
|
return GeneralizedIndex(MAX_CROSSLINK_SIZE // SHARD_HEADER_SIZE + index)
|
|
```
|
|
|
|
#### `process_shard_receipt`
|
|
|
|
```python
|
|
def process_shard_receipt(state: BeaconState, receipt_proof: ShardReceiptProof):
|
|
"""
|
|
Processes a ShardReceipt object.
|
|
"""
|
|
receipt_slot = state.next_shard_receipt_period[receipt_proof.shard] * SLOTS_PER_EPOCH * EPOCHS_PER_SHARD_PERIOD
|
|
first_slot_in_last_crosslink = state.current_crosslinks[receipt_proof.shard].start_epoch * SLOTS_PER_EPOCH
|
|
gindex = concat_generalized_indices(
|
|
get_generalized_index_of_crosslink_header(0),
|
|
get_generalized_index(ShardBlockHeader, 'state_root'),
|
|
compute_historical_state_generalized_index(receipt_slot, first_slot_in_last_crosslink),
|
|
get_generalized_index(ShardState, 'receipt_root')
|
|
)
|
|
assert verify_merkle_proof(
|
|
leaf=hash_tree_root(receipt_proof.receipt),
|
|
proof=receipt_proof.proof,
|
|
index=gindex,
|
|
root=state.current_crosslinks[shard].data_root
|
|
)
|
|
for delta in receipt_proof.receipt:
|
|
if get_current_epoch(state) < state.validators[delta.index].withdrawable_epoch:
|
|
increase_balance(state, delta.index, state.validators[delta.index].effective_balance * delta.reward_coefficient // REWARD_COEFFICIENT_BASE)
|
|
decrease_balance(state, delta.index, delta.block_fee)
|
|
state.next_shard_receipt_period[receipt_proof.shard] += 1
|
|
increase_balance(state, get_beacon_proposer_index(state), MICRO_REWARD)
|
|
```
|
|
|
|
## Changes
|
|
|
|
### Persistent committees
|
|
|
|
Add to the beacon state the following fields:
|
|
|
|
```python
|
|
# begin insert @persistent_committee_fields
|
|
previous_persistent_committee_root: Hash
|
|
current_persistent_committee_root: Hash
|
|
next_persistent_committee_root: Hash
|
|
next_shard_receipt_period: Vector[uint, SHARD_COUNT]
|
|
# end insert @persistent_committee_fields
|
|
```
|
|
`next_shard_receipt_period` values initialized to `PHASE_1_FORK_SLOT // SLOTS_PER_EPOCH // EPOCHS_PER_SHARD_PERIOD`
|
|
|
|
Run `update_persistent_committee` immediately before `process_final_updates`:
|
|
|
|
```python
|
|
# begin insert @update_persistent_committee
|
|
update_persistent_committee(state)
|
|
# end insert @update_persistent_committee
|
|
def update_persistent_committee(state: BeaconState) -> None:
|
|
"""
|
|
Updates persistent committee roots at boundary blocks.
|
|
"""
|
|
if (get_current_epoch(state) + 1) % EPOCHS_PER_SHARD_PERIOD == 0:
|
|
state.previous_persistent_committee_root = state.current_persistent_committee_root
|
|
state.current_persistent_committee_root = state.next_persistent_committee_root
|
|
committees = Vector[CompactCommittee, SHARD_COUNT]([
|
|
committee_to_compact_committee(state, get_period_committee(state, get_current_epoch(state) + 1, i))
|
|
for i in range(SHARD_COUNT)
|
|
])
|
|
state.next_persistent_committee_root = hash_tree_root(committees)
|
|
```
|
|
|
|
### Shard receipt processing
|
|
|
|
Add the `shard_receipts` operation to `BeaconBlockBody`:
|
|
|
|
```python
|
|
# begin insert @shard_receipts
|
|
shard_receipts: List[ShardReceipt, MAX_SHARD_RECEIPTS]
|
|
# end insert @shard_receipts
|
|
```
|
|
|
|
Use `process_shard_receipt` to process each receipt.
|
|
|
|
```python
|
|
# begin insert @process_shard_receipts
|
|
(body.shard_receipts, process_shard_receipts),
|
|
# end insert @process_shard_receipts
|
|
```
|