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Hsiao-Wei Wang 2018-11-26 17:14:42 +08:00
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specs/core/0_beacon-chain.md
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@ -150,7 +150,7 @@ An `AttestationRecord` has the following fields:
'last_crosslink_hash': 'hash32', 'last_crosslink_hash': 'hash32',
# Root of data between last hash and this one # Root of data between last hash and this one
'shard_block_combined_data_root': 'hash32', 'shard_block_combined_data_root': 'hash32',
# Attester participation bitfield (1 bit per attester) # Attester participation bitfield (2 bits per attester)
'attester_bitfield': 'bytes', 'attester_bitfield': 'bytes',
# Slot of last justified beacon block # Slot of last justified beacon block
'justified_slot': 'uint64', 'justified_slot': 'uint64',
@ -577,7 +577,7 @@ We define another set of helpers to be used throughout: `bytes1(x): return x.to_
We define a function to determine the balance of a validator used for determining punishments and calculating stake: We define a function to determine the balance of a validator used for determining punishments and calculating stake:
```python ```python
def balance_at_stake(validator): def balance_at_stake(validator: ValidatorRecord) -> int:
return min(validator.balance, DEPOSIT_SIZE) return min(validator.balance, DEPOSIT_SIZE)
``` ```
@ -825,7 +825,7 @@ def exit_validator(index, state, block, penalize, current_slot):
This procedure should be carried out every beacon block. This procedure should be carried out every beacon block.
* Let `parent_hash` be the hash of the immediate previous beacon block (ie. equal to `ancestor_hashes[0]`). * Let `parent_hash` be the hash of the immediate previous beacon block (ie. equal to `ancestor_hashes[0]`).
* Let `parent` be the beacon block with the hash `parent_hash` * Let `parent` be the beacon block with the hash `parent_hash`.
First, set `recent_block_hashes` to the output of the following: First, set `recent_block_hashes` to the output of the following:
@ -860,10 +860,11 @@ For each `AttestationRecord` object `obj`:
* Verify that `justified_block_hash` is the hash of the block in the current chain at the slot -- `justified_slot`. * Verify that `justified_block_hash` is the hash of the block in the current chain at the slot -- `justified_slot`.
* Verify that either `last_crosslink_hash` or `shard_block_hash` equals `state.crosslinks[shard].shard_block_hash`. * Verify that either `last_crosslink_hash` or `shard_block_hash` equals `state.crosslinks[shard].shard_block_hash`.
* Compute `full_parent_hashes` = `[get_block_hash(state, block, slot - CYCLE_LENGTH + i) for i in range(1, CYCLE_LENGTH - len(parent_hashes) + 1)] + parent_hashes` (eg, if `CYCLE_LENGTH = 4`, `slot = 5`, the actual block hashes starting from slot 0 are `Z A B C D E F G H I J`, and `parent_hashes = [D', E']` then `full_parent_hashes = [B, C, D' E']`). Note that when *creating* an attestation for a block, the hash of that block itself won't yet be in the `state`, so you would need to add it explicitly. * Compute `full_parent_hashes` = `[get_block_hash(state, block, slot - CYCLE_LENGTH + i) for i in range(1, CYCLE_LENGTH - len(parent_hashes) + 1)] + parent_hashes` (eg, if `CYCLE_LENGTH = 4`, `slot = 5`, the actual block hashes starting from slot 0 are `Z A B C D E F G H I J`, and `parent_hashes = [D', E']` then `full_parent_hashes = [B, C, D' E']`). Note that when *creating* an attestation for a block, the hash of that block itself won't yet be in the `state`, so you would need to add it explicitly.
* Let `bit0_attestation_indices, bit1_attestation_indices = get_attestation_participants(state, obj)` (and verify that the method returns successfully) * `aggregate_sig` verification:
* Let `bit0_group_public_key = BLSAddPubkeys(bit0_attestation_indices)` and `bit1_group_public_key = BLSAddPubkeys(bit1_attestation_indices)` * Let `bit0_attestation_indices, bit1_attestation_indices = get_attestation_participants(state, obj)` (and verify that the method returns successfully)
* Let `data = AttestationSignedData(slot, shard, parent_hashes, shard_block_hash, last_crosslinked_hash, shard_block_combined_data_root, justified_slot)`. * Let `bit0_group_public_key = BLSAddPubkeys(bit0_attestation_indices)` and `bit1_group_public_key = BLSAddPubkeys(bit1_attestation_indices)`.
* Check `BLSVerify(pubkey=group_public_key, msg=data, sig=aggregate_sig, domain=get_domain(state, slot, DOMAIN_ATTESTATION))`. * Let `data = AttestationSignedData(slot, shard, parent_hashes, shard_block_hash, last_crosslinked_hash, shard_block_combined_data_root, justified_slot)`.
* Check `BLSVerify(pubkey=group_public_key, msg=data, sig=aggregate_sig, domain=get_domain(state, slot, DOMAIN_ATTESTATION))`.
* [TO BE REMOVED IN PHASE 1] Verify that `shard_block_hash == bytes([0] * 32)`. * [TO BE REMOVED IN PHASE 1] Verify that `shard_block_hash == bytes([0] * 32)`.
Extend the list of `AttestationRecord` objects in the `state` with those included in the block, ordering the new additions in the same order as they came in the block, and replacing `obj.parent_hashes` with the calculated value of `full_parent_hashes`. Extend the list of `AttestationRecord` objects in the `state` with those included in the block, ordering the new additions in the same order as they came in the block, and replacing `obj.parent_hashes` with the calculated value of `full_parent_hashes`.
@ -983,16 +984,16 @@ _Note: `last_state_recalculation_slot` will always be a multiple of `CYCLE_LENGT
#### Precomputation #### Precomputation
* Let `active_validators = [state.validators[i] for i in get_active_validator_indices(state.validators)]` * Let `active_validators = [state.validators[i] for i in get_active_validator_indices(state.validators)]`.
* Let `total_balance = sum([balance_at_stake(v) for v in active_validators])` * Let `total_balance = sum([balance_at_stake(v) for v in active_validators])`.
* Let `this_cycle_attestations = [a for a in state.pending_attestations if s <= a.slot < s + CYCLE_LENGTH]` (note: this is the set of attestations _of slots in the cycle `s...s+CYCLE_LENGTH-1`_, not attestations _that got included in the chain during the cycle `s...s+CYCLE_LENGTH-1`_) * Let `this_cycle_attestations = [a for a in state.pending_attestations if s <= a.slot < s + CYCLE_LENGTH]`. (note: this is the set of attestations _of slots in the cycle `s...s+CYCLE_LENGTH-1`_, not attestations _that got included in the chain during the cycle `s...s+CYCLE_LENGTH-1`_)
* Let `prev_cycle_attestations = [a for a in state.pending_attestations if s - CYCLE_LENGTH <= a.slot < s]` * Let `prev_cycle_attestations = [a for a in state.pending_attestations if s - CYCLE_LENGTH <= a.slot < s]`.
* Let `this_cycle_s_attestations = [a for a in this_cycle_attestations if get_block_hash(state, block, s) in a.parent_hashes and a.justified_slot == state.justification_source]` * Let `this_cycle_s_attestations = [a for a in this_cycle_attestations if get_block_hash(state, block, s) in a.parent_hashes and a.justified_slot == state.justification_source]`.
* Let `prev_s_attestations = [a for a in this_cycle_attestations + prev_cycle_attestations if get_block_hash(state, block, s - CYCLE_LENGTH) in a.parent_hashes and a.justified_slot == state.prev_cycle_justification_source]` * Let `prev_s_attestations = [a for a in this_cycle_attestations + prev_cycle_attestations if get_block_hash(state, block, s - CYCLE_LENGTH) in a.parent_hashes and a.justified_slot == state.prev_cycle_justification_source]`.
* Let `s_attesters` be the union of the validator index sets given by `[get_attestation_participants(state, a) for a in this_cycle_s_attestations]` * Let `s_attesters` be the union of the validator index sets given by `[get_attestation_participants(state, a) for a in this_cycle_s_attestations]`.
* Let `prev_s_attesters` be the union of the validator index sets given by `[get_attestation_participants(state, a) for a in prev_s_attestations]` * Let `prev_s_attesters` be the union of the validator index sets given by `[get_attestation_participants(state, a) for a in prev_s_attestations]`.
* Let `total_balance_attesting_at_s = sum([balance_at_stake(v) for v in s_attesters])` * Let `total_balance_attesting_at_s = sum([balance_at_stake(v) for v in s_attesters])`.
* Let `total_balance_attesting_at_prev_s = sum([balance_at_stake(v) for v in prev_s_attesters])` * Let `total_balance_attesting_at_prev_s = sum([balance_at_stake(v) for v in prev_s_attesters])`.
* For every `ShardAndCommittee` object `obj` in `shard_and_committee_for_slots`, let: * For every `ShardAndCommittee` object `obj` in `shard_and_committee_for_slots`, let:
* `attesting_validators(obj, shard_block_hash)` be the union of the validator index sets given by `[get_attestation_participants(state, a) for a in this_cycle_attestations + prev_cycle_attestations if a.shard == obj.shard and a.shard_block_hash == shard_block_hash]` * `attesting_validators(obj, shard_block_hash)` be the union of the validator index sets given by `[get_attestation_participants(state, a) for a in this_cycle_attestations + prev_cycle_attestations if a.shard == obj.shard and a.shard_block_hash == shard_block_hash]`
* `attesting_validators(obj)` be equal to `attesting_validators(obj, shard_block_hash)` for the value of `shard_block_hash` such that `sum([balance_at_stake(v) for v in attesting_validators(obj, shard_block_hash)])` is maximized (ties broken by favoring lower `shard_block_hash` values) * `attesting_validators(obj)` be equal to `attesting_validators(obj, shard_block_hash)` for the value of `shard_block_hash` such that `sum([balance_at_stake(v) for v in attesting_validators(obj, shard_block_hash)])` is maximized (ties broken by favoring lower `shard_block_hash` values)
@ -1003,7 +1004,7 @@ _Note: `last_state_recalculation_slot` will always be a multiple of `CYCLE_LENGT
Let `inclusion_slot(a)` equal the slot in which attestation `a` was included, and `inclusion_distance(a) = inclusion_slot(a) - a.slot`. Let `inclusion_slot(v)` equal `inclusion_distance(a)` for the attestation `a` where `v` is in `get_attestation_participants(state, a)`, and define `inclusion_distance(v)` similarly. We define a function `adjust_for_inclusion_distance(magnitude, dist)` which adjusts the reward of an attestation based on how long it took to get included (the longer, the lower the reward). Returns a value between 0 and `magnitude` Let `inclusion_slot(a)` equal the slot in which attestation `a` was included, and `inclusion_distance(a) = inclusion_slot(a) - a.slot`. Let `inclusion_slot(v)` equal `inclusion_distance(a)` for the attestation `a` where `v` is in `get_attestation_participants(state, a)`, and define `inclusion_distance(v)` similarly. We define a function `adjust_for_inclusion_distance(magnitude, dist)` which adjusts the reward of an attestation based on how long it took to get included (the longer, the lower the reward). Returns a value between 0 and `magnitude`
```python ```python
def adjust_for_inclusion_distance(magnitude, dist): def adjust_for_inclusion_distance(magnitude: int, dist: int) -> int:
return magnitude // 2 + (magnitude // 2) * MIN_ATTESTATION_INCLUSION_DELAY // dist return magnitude // 2 + (magnitude // 2) * MIN_ATTESTATION_INCLUSION_DELAY // dist
``` ```
@ -1214,7 +1215,6 @@ Note: This spec is ~65% complete.
* [ ] Add penalties for deposits below 32 ETH (or some other threshold) * [ ] Add penalties for deposits below 32 ETH (or some other threshold)
* [ ] Add a `SpecialRecord` to (re)register * [ ] Add a `SpecialRecord` to (re)register
# Appendix # Appendix
## Appendix A - Hash function ## Appendix A - Hash function