status-im
/
eth2.0-specs
mirror of https://github.com/status-im/eth2.0-specs.git
2
0
Fork 0
Code Issues Projects Releases Wiki Activity

Attestation data contains latest crosslink, not just latest crosslink data 

The reason to do this is that it makes it calculable from inside an attestation how many epochs the attestation spans over, which is needed for proof of custody reasons. It's a relatively small change and so arguably easier to do now than to do as a patch in phase 1.

Note that this changes the meaning of latest_crosslink.epoch, from the epoch when the latest crosslink was included to the epoch that the latest crosslink was for. This affects the line:

* `state.latest_crosslinks[shard].epoch > state.validator_registry_update_epoch` for every shard number `shard` in `[(state.current_epoch_start_shard + i) % SHARD_COUNT for i in range(get_current_epoch_committee_count(state))]` (that is, for every shard in the current committees)

But this may actually make it _more_ correct, as it means that in the case where >512 shards are processed per epoch, and so a committee from the previous epoch could get finalized in the current epoch, that would no longer count toward every shard having received a "new" crosslink.
This commit is contained in:
vbuterin 2019-02-07 19:34:54 -06:00 committed by GitHub
parent 1582413151
commit 086df84bdc
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
specs/core/0_beacon-chain.md
View File

@ -362,8 +362,8 @@ The following data structures are defined as [SimpleSerialize (SSZ)](https://git
'epoch_boundary_root': 'bytes32',
# Shard block's hash of root
'shard_block_root': 'bytes32',
# Last crosslink's hash of root
'latest_crosslink_root': 'bytes32',
# Last crosslink
'latest_crosslink': Crosslink,
# Last justified epoch in the beacon state
'justified_epoch': 'uint64',
# Hash of the last justified beacon block
@ -1688,7 +1688,7 @@ For each `attestation` in `block.body.attestations`:
* Verify that `attestation.data.slot <= state.slot - MIN_ATTESTATION_INCLUSION_DELAY < attestation.data.slot + EPOCH_LENGTH`.
* Verify that `attestation.data.justified_epoch` is equal to `state.justified_epoch if attestation.data.slot >= get_epoch_start_slot(get_current_epoch(state)) else state.previous_justified_epoch`.
* Verify that `attestation.data.justified_block_root` is equal to `get_block_root(state, get_epoch_start_slot(attestation.data.justified_epoch))`.
* Verify that either `attestation.data.latest_crosslink_root` or `attestation.data.shard_block_root` equals `state.latest_crosslinks[attestation.data.shard].shard_block_root`.
* Verify that either (i) `state.latest_crosslinks[attestation.data.shard] == attestation.data.latest_crosslink` or (ii) `state.latest_crosslinks[attestation.data.shard] == Crosslink(shard_block_root=attestation.data.shard_block_root, epoch=slot_to_epoch(attestation.data.slot))`
* Verify bitfields and aggregate signature:
```python
@ -1860,7 +1860,7 @@ Finally, update the following:
For every `slot in range(get_epoch_start_slot(previous_epoch), get_epoch_start_slot(next_epoch))`, let `crosslink_committees_at_slot = get_crosslink_committees_at_slot(state, slot)`. For every `(crosslink_committee, shard)` in `crosslink_committees_at_slot`, compute:
* Set `state.latest_crosslinks[shard] = Crosslink(epoch=current_epoch, shard_block_root=winning_root(crosslink_committee))` if `3 * total_attesting_balance(crosslink_committee) >= 2 * get_total_balance(crosslink_committee)`.
* Set `state.latest_crosslinks[shard] = Crosslink(epoch=slot_to_epoch(slot), shard_block_root=winning_root(crosslink_committee))` if `3 * total_attesting_balance(crosslink_committee) >= 2 * get_total_balance(crosslink_committee)`.
#### Rewards and penalties