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Update v-guide wrt recent spec updates #1253

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merged 3 commits into from
Jul 1, 2019
Merged

Update v-guide wrt recent spec updates #1253

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f7ed186
Use `Checkpoint`
hwwhww Jul 1, 2019
4f360a5
Fix outdated `fork.slot` and `attestation_data.slot`
hwwhww Jul 1, 2019
200da4d
Merge branch 'dev' into v_guide_checkpoint
djrtwo Jul 1, 2019
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10 changes: 4 additions & 6 deletions specs/validator/0_beacon-chain-validator.md
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Expand Up @@ -293,10 +293,8 @@ Set `attestation_data.beacon_block_root = signing_root(head_block)`.

##### FFG vote

- Set `attestation_data.source_epoch = head_state.current_justified_epoch`.
- Set `attestation_data.source_root = head_state.current_justified_root`.
- Set `attestation_data.target_epoch = get_current_epoch(head_state)`
- Set `attestation_data.target_root = epoch_boundary_block_root` where `epoch_boundary_block_root` is the root of block at the most recent epoch boundary.
- Set `attestation_data.source = head_state.current_justified_checkpoint`.
- Set `attestation_data.target = Checkpoint(epoch=get_current_epoch(head_state), root=epoch_boundary_block_root)` where `epoch_boundary_block_root` is the root of block at the most recent epoch boundary.

*Note*: `epoch_boundary_block_root` can be looked up in the state using:

Expand All @@ -310,7 +308,7 @@ Construct `attestation_data.crosslink` via the following.
- Set `attestation_data.crosslink.shard = shard` where `shard` is the shard associated with the validator's committee.
- Let `parent_crosslink = head_state.current_crosslinks[shard]`.
- Set `attestation_data.crosslink.start_epoch = parent_crosslink.end_epoch`.
- Set `attestation_data.crosslink.end_epoch = min(attestation_data.target_epoch, parent_crosslink.end_epoch + MAX_EPOCHS_PER_CROSSLINK)`.
- Set `attestation_data.crosslink.end_epoch = min(attestation_data.target.epoch, parent_crosslink.end_epoch + MAX_EPOCHS_PER_CROSSLINK)`.
- Set `attestation_data.crosslink.parent_root = hash_tree_root(head_state.current_crosslinks[shard])`.
- Set `attestation_data.crosslink.data_root = ZERO_HASH`. *Note*: This is a stub for Phase 0.

Expand Down Expand Up @@ -374,7 +372,7 @@ To avoid "attester slashings", a validator must not sign two conflicting [`Attes

Specifically, when signing an `Attestation`, a validator should perform the following steps in the following order:

1. Save a record to hard disk that an attestation has been signed for source (i.e. `attestation_data.source_epoch`) and target (i.e. `compute_epoch_of_slot(attestation_data.slot)`).
1. Save a record to hard disk that an attestation has been signed for source (i.e. `attestation_data.source.epoch`) and target (i.e. `attestation_data.target.epoch`).
2. Generate and broadcast attestation.

If the software crashes at some point within this routine, then when the validator comes back online, the hard disk has the record of the *potentially* signed/broadcast attestation and can effectively avoid slashing.