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Update casper_sharding_v2.1.md

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vbuterin 2018-10-03 22:02:04 -04:00 committed by GitHub
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@ -126,6 +126,20 @@ fields = {
}
```
Here's the data signed (`AttestationSignedData`):
```python
fields = {
# Version of the chain
'version': 'int64',
'slot': 'int64',
'parent_hashes': ['hash32'],
'shard_id': 'int16',
'shard_block_hash': 'hash32',
'justified_slot': 'int64'
}
```
#### Beacon chain state
The beacon chain state is split into two parts, _active state_ and _crystallized state_.
@ -460,7 +474,8 @@ For each one of these attestations:
* Let `attestation_indices` be `get_shards_and_committees_for_slot(crystallized_state, slot)[x]`, choosing `x` so that `attestation_indices.shard_id` equals the `shard_id` value provided to find the set of validators that is creating this attestation record.
* Verify that `len(attester_bitfield) == ceil_div8(len(attestation_indices))`, where `ceil_div8 = (x + 7) // 8`. Verify that bits `len(attestation_indices)....` and higher, if present (i.e. `len(attestation_indices)` is not a multiple of 8), are all zero
* Derive a group public key by adding the public keys of all of the attesters in `attestation_indices` for whom the corresponding bit in `attester_bitfield` (the ith bit is `(attester_bitfield[i // 8] >> (7 - (i %8))) % 2`) equals 1
* Let `version = pre_fork_version if slot < fork_slot_number else post_fork_version`. Verify that `aggregate_sig` verifies using the group pubkey generated and `hash(bytes4(version) + bytes8(slot) + parent_hashes + bytes2(shard_id) + shard_block_hash + bytes8(justified_slot))` as the message.
* Let `version = pre_fork_version if slot < fork_slot_number else post_fork_version`.
* Verify that `aggregate_sig` verifies using the group pubkey generated and the serialized form of `AttestationSignedData(version, slot, parent_hashes, shard_id, shard_block_hash, crystallized_state.last_justified_slot)` as the message.
Extend the list of `AttestationRecord` objects in the `active_state` with those included in the block, ordering the new additions in the same order as they came in the block. Similarly extend the list of `SpecialObject` objects in the `active_state` with those included in the block.