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Proposal committee -> persistent committee

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vbuterin 2019-02-08 03:48:58 -06:00 committed by GitHub
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specs/core/1_shard-data-chains.md
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@ -16,11 +16,11 @@ Ethereum 2.0 consists of a central beacon chain along with `SHARD_COUNT` shard c
Phase 1 depends upon all of the constants defined in [Phase 0](0_beacon-chain.md#constants) in addition to the following: Phase 1 depends upon all of the constants defined in [Phase 0](0_beacon-chain.md#constants) in addition to the following:
| Constant | Value | Unit | Approximation | | Constant | Value | Unit | Approximation |
|-----------------------------|------------------|--------|---------------| |-------------------------------|------------------|--------|---------------|
| `SHARD_CHUNK_SIZE` | 2**5 (= 32) | bytes | | | `SHARD_CHUNK_SIZE` | 2**5 (= 32) | bytes | |
| `SHARD_BLOCK_SIZE` | 2**14 (= 16,384) | bytes | | | `SHARD_BLOCK_SIZE` | 2**14 (= 16,384) | bytes | |
| `PROPOSAL_RESHUFFLE_PERIOD` | 2**11 (= 2,048) | epochs | 9 days | | `PERSISTENT_COMMITTEE_PERIOD` | 2**11 (= 2,048) | epochs | 9 days |
### Flags, domains, etc. ### Flags, domains, etc.
@ -73,21 +73,21 @@ To validate a block header on shard `shard_id`, compute as follows:
* Let `proposer_index = hash(state.randao_mix + int_to_bytes8(shard_id) + int_to_bytes8(slot)) % len(validators)`. Let `msg` be the block but with the `block.signature` set to `[0, 0]`. Verify that `BLSVerify(pub=validators[proposer_index].pubkey, msg=hash(msg), sig=block.signature, domain=get_domain(state, slot, SHARD_PROPOSER_DOMAIN))` passes. * Let `proposer_index = hash(state.randao_mix + int_to_bytes8(shard_id) + int_to_bytes8(slot)) % len(validators)`. Let `msg` be the block but with the `block.signature` set to `[0, 0]`. Verify that `BLSVerify(pub=validators[proposer_index].pubkey, msg=hash(msg), sig=block.signature, domain=get_domain(state, slot, SHARD_PROPOSER_DOMAIN))` passes.
* Let `group_public_key = bls_aggregate_pubkeys([state.validators[index].pubkey for i, index in enumerate(persistent_committee) if get_bitfield_bit(participation_bitfield, i) is True])`. Verify that `bls_verify(pubkey=group_public_key, message_hash=parent_root, sig=block.aggregate_signature, domain=get_domain(state, slot, SHARD_ATTESTER_DOMAIN))` passes. * Let `group_public_key = bls_aggregate_pubkeys([state.validators[index].pubkey for i, index in enumerate(persistent_committee) if get_bitfield_bit(participation_bitfield, i) is True])`. Verify that `bls_verify(pubkey=group_public_key, message_hash=parent_root, sig=block.aggregate_signature, domain=get_domain(state, slot, SHARD_ATTESTER_DOMAIN))` passes.
We define the helper `get_proposal_committee` as follows: We define the helper `get_persistent_committee` as follows:
```python ```python
def get_proposal_committee(seed: Bytes32, def get_persistent_commmitee(seed: Bytes32,
validators: List[Validator], validators: List[Validator],
shard: ShardNumber, shard: ShardNumber,
epoch: EpochNumber) -> List[ValidatorIndex]: epoch: EpochNumber) -> List[ValidatorIndex]:
earlier_committee_start = epoch - (epoch % PROPOSAL_RESHUFFLE_PERIOD) - PROPOSAL_RESHUFFLE_PERIOD * 2 earlier_committee_start = epoch - (epoch % PERSISTENT_COMMITTEE_PERIOD) - PERSISTENT_COMMITTEE_PERIOD * 2
earlier_committee = split(shuffle( earlier_committee = split(shuffle(
get_active_validator_indices(validators, earlier_committee_start), get_active_validator_indices(validators, earlier_committee_start),
generate_seed(state, earlier_committee_start) generate_seed(state, earlier_committee_start)
), SHARD_COUNT)[shard] ), SHARD_COUNT)[shard]
later_committee_start = epoch - (epoch % PROPOSAL_RESHUFFLE_PERIOD) - PROPOSAL_RESHUFFLE_PERIOD later_committee_start = epoch - (epoch % PERSISTENT_COMMITTEE_PERIOD) - PERSISTENT_COMMITTEE_PERIOD
later_committee = split(shuffle( later_committee = split(shuffle(
get_active_validator_indices(validators, later_committee_start), get_active_validator_indices(validators, later_committee_start),
generate_seed(state, later_committee_start) generate_seed(state, later_committee_start)
@ -96,12 +96,12 @@ def get_proposal_committee(seed: Bytes32,
def get_switchover_epoch(index): def get_switchover_epoch(index):
return ( return (
bytes_to_int(hash(generate_seed(state, earlier_committee_start) + bytes3(index))[0:8]) % bytes_to_int(hash(generate_seed(state, earlier_committee_start) + bytes3(index))[0:8]) %
PROPOSAL_RESHUFFLE_PERIOD PERSISTENT_COMMITTEE_PERIOD
) )
return ( return (
[i for i in earlier_committee if epoch % PROPOSAL_RESHUFFLE_PERIOD < get_switchover_epoch(i)] + [i for i in earlier_committee if epoch % PERSISTENT_COMMITTEE_PERIOD < get_switchover_epoch(i)] +
[i for i in later_committee if epoch % PROPOSAL_RESHUFFLE_PERIOD >= get_switchover_epoch(i)] [i for i in later_committee if epoch % PERSISTENT_COMMITTEE_PERIOD >= get_switchover_epoch(i)]
) )
``` ```