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Slashing penalty calculation change (#1217)

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If the exit queue is very long, then a validator may take many months to exit. With the code as currently written, however, self-slashing is a potentially lucrative route to get one's money out faster, because one can exit in 36 days.

This PR changes it so that slashing can only extend your withdrawal time, not contract it. Also, instead of the slashed balances used to calculate one's slashing penalty being those in `[withdrawal - 54 days ... withdrawal - 18 days]`, we now run the penalization algorithm once every 36 days that a validator is slashed but not withdrawn, so that it covers the 36-day period where the validator was actually slashed.  It also moves the minimum slashing penalty to the `slash_validator` function so that it is only applied once.

We also simplify the `slashed_balances` logic to be per-epoch.
This commit is contained in:
vbuterin 2019-06-28 21:35:26 +08:00 committed by Justin
parent 0ba933e088
commit c764202a57
5 changed files with 92 additions and 46 deletions
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4
configs/constant_presets/mainnet.yaml
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@ -76,7 +76,7 @@ MIN_EPOCHS_TO_INACTIVITY_PENALTY: 4
# 2**16 (= 65,536) epochs ~0.8 years
EPOCHS_PER_HISTORICAL_VECTOR: 65536
# 2**13 (= 8,192) epochs ~36 days
EPOCHS_PER_SLASHED_BALANCES_VECTOR: 8192
EPOCHS_PER_SLASHINGS_VECTOR: 8192
# 2**24 (= 16,777,216) historical roots, ~26,131 years
HISTORICAL_ROOTS_LIMIT: 16777216
# 2**40 (= 1,099,511,627,776) validator spots
@ -88,7 +88,7 @@ VALIDATOR_REGISTRY_LIMIT: 1099511627776
# 2**5 (= 32)
BASE_REWARD_FACTOR: 32
# 2**9 (= 512)
WHISTLEBLOWING_REWARD_QUOTIENT: 512
WHISTLEBLOWER_REWARD_QUOTIENT: 512
# 2**3 (= 8)
PROPOSER_REWARD_QUOTIENT: 8
# 2**25 (= 33,554,432)

4
configs/constant_presets/minimal.yaml
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@ -77,7 +77,7 @@ EARLY_DERIVED_SECRET_PENALTY_MAX_FUTURE_EPOCHS: 4096
# [customized] smaller state
EPOCHS_PER_HISTORICAL_VECTOR: 64
# [customized] smaller state
EPOCHS_PER_SLASHED_BALANCES_VECTOR: 64
EPOCHS_PER_SLASHINGS_VECTOR: 64
# 2**24 (= 16,777,216) historical roots
HISTORICAL_ROOTS_LIMIT: 16777216
# 2**40 (= 1,099,511,627,776) validator spots
@ -89,7 +89,7 @@ VALIDATOR_REGISTRY_LIMIT: 1099511627776
# 2**5 (= 32)
BASE_REWARD_FACTOR: 32
# 2**9 (= 512)
WHISTLEBLOWING_REWARD_QUOTIENT: 512
WHISTLEBLOWER_REWARD_QUOTIENT: 512
# 2**3 (= 8)
PROPOSER_REWARD_QUOTIENT: 8
# 2**25 (= 33,554,432)

44
specs/core/0_beacon-chain.md
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@ -234,7 +234,7 @@ The following values are (non-configurable) constants used throughout the specif
| Name | Value | Unit | Duration |
| - | - | :-: | :-: |
| `EPOCHS_PER_HISTORICAL_VECTOR` | `2**16` (= 65,536) | epochs | ~0.8 years |
| `EPOCHS_PER_SLASHED_BALANCES_VECTOR` | `2**13` (= 8,192) | epochs | ~36 days |
| `EPOCHS_PER_SLASHINGS_VECTOR` | `2**13` (= 8,192) | epochs | ~36 days |
| `HISTORICAL_ROOTS_LIMIT` | `2**24` (= 16,777,216) | historical roots | ~26,131 years |
| `VALIDATOR_REGISTRY_LIMIT` | `2**40` (= 1,099,511,627,776) | validator spots | |
@ -243,7 +243,7 @@ The following values are (non-configurable) constants used throughout the specif
| Name | Value |
| - | - |
| `BASE_REWARD_FACTOR` | `2**6` (= 64) |
| `WHISTLEBLOWING_REWARD_QUOTIENT` | `2**9` (= 512) |
| `WHISTLEBLOWER_REWARD_QUOTIENT` | `2**9` (= 512) |
| `PROPOSER_REWARD_QUOTIENT` | `2**3` (= 8) |
| `INACTIVITY_PENALTY_QUOTIENT` | `2**25` (= 33,554,432) |
| `MIN_SLASHING_PENALTY_QUOTIENT` | `2**5` (= 32) |
@ -520,7 +520,7 @@ class BeaconState(Container):
randao_mixes: Vector[Hash, EPOCHS_PER_HISTORICAL_VECTOR]
active_index_roots: Vector[Hash, EPOCHS_PER_HISTORICAL_VECTOR] # Active registry digests for light clients
# Slashings
slashed_balances: Vector[Gwei, EPOCHS_PER_SLASHED_BALANCES_VECTOR] # Sums of slashed effective balances
slashings: Vector[Gwei, EPOCHS_PER_SLASHINGS_VECTOR] # Per-epoch sums of slashed effective balances
# Attestations
previous_epoch_attestations: List[PendingAttestation, MAX_ATTESTATIONS * SLOTS_PER_EPOCH]
current_epoch_attestations: List[PendingAttestation, MAX_ATTESTATIONS * SLOTS_PER_EPOCH]
@ -1097,21 +1097,22 @@ def slash_validator(state: BeaconState,
"""
Slash the validator with index ``slashed_index``.
"""
current_epoch = get_current_epoch(state)
epoch = get_current_epoch(state)
initiate_validator_exit(state, slashed_index)
state.validators[slashed_index].slashed = True
state.validators[slashed_index].withdrawable_epoch = Epoch(current_epoch + EPOCHS_PER_SLASHED_BALANCES_VECTOR)
slashed_balance = state.validators[slashed_index].effective_balance
state.slashed_balances[current_epoch % EPOCHS_PER_SLASHED_BALANCES_VECTOR] += slashed_balance
validator = state.validators[slashed_index]
validator.slashed = True
validator.withdrawable_epoch = max(validator.withdrawable_epoch, Epoch(epoch + EPOCHS_PER_SLASHINGS_VECTOR))
state.slashings[epoch % EPOCHS_PER_SLASHINGS_VECTOR] += validator.effective_balance
decrease_balance(state, slashed_index, validator.effective_balance // MIN_SLASHING_PENALTY_QUOTIENT)
# Apply proposer and whistleblower rewards
proposer_index = get_beacon_proposer_index(state)
if whistleblower_index is None:
whistleblower_index = proposer_index
whistleblowing_reward = Gwei(slashed_balance // WHISTLEBLOWING_REWARD_QUOTIENT)
proposer_reward = Gwei(whistleblowing_reward // PROPOSER_REWARD_QUOTIENT)
whistleblower_reward = Gwei(validator.effective_balance // WHISTLEBLOWER_REWARD_QUOTIENT)
proposer_reward = Gwei(whistleblower_reward // PROPOSER_REWARD_QUOTIENT)
increase_balance(state, proposer_index, proposer_reward)
increase_balance(state, whistleblower_index, whistleblowing_reward - proposer_reward)
decrease_balance(state, slashed_index, whistleblowing_reward)
increase_balance(state, whistleblower_index, whistleblower_reward - proposer_reward)
```
## Genesis
@ -1493,18 +1494,9 @@ def process_registry_updates(state: BeaconState) -> None:
def process_slashings(state: BeaconState) -> None:
epoch = get_current_epoch(state)
total_balance = get_total_active_balance(state)
# Compute slashed balances in the current epoch
total_at_start = state.slashed_balances[(epoch + 1) % EPOCHS_PER_SLASHED_BALANCES_VECTOR]
total_at_end = state.slashed_balances[epoch % EPOCHS_PER_SLASHED_BALANCES_VECTOR]
total_penalties = total_at_end - total_at_start
for index, validator in enumerate(state.validators):
if validator.slashed and epoch + EPOCHS_PER_SLASHED_BALANCES_VECTOR // 2 == validator.withdrawable_epoch:
penalty = max(
validator.effective_balance * min(total_penalties * 3, total_balance) // total_balance,
validator.effective_balance // MIN_SLASHING_PENALTY_QUOTIENT
)
if validator.slashed and epoch + EPOCHS_PER_SLASHINGS_VECTOR // 2 == validator.withdrawable_epoch:
penalty = validator.effective_balance * min(sum(state.slashings) * 3, total_balance) // total_balance
decrease_balance(state, ValidatorIndex(index), penalty)
```
@ -1532,10 +1524,8 @@ def process_final_updates(state: BeaconState) -> None:
get_active_validator_indices(state, Epoch(next_epoch + ACTIVATION_EXIT_DELAY))
)
)
# Set total slashed balances
state.slashed_balances[next_epoch % EPOCHS_PER_SLASHED_BALANCES_VECTOR] = (
state.slashed_balances[current_epoch % EPOCHS_PER_SLASHED_BALANCES_VECTOR]
)
# Reset slashings
state.slashings[next_epoch % EPOCHS_PER_SLASHINGS_VECTOR] = Gwei(0)
# Set randao mix
state.randao_mixes[next_epoch % EPOCHS_PER_HISTORICAL_VECTOR] = get_randao_mix(state, current_epoch)
# Set historical root accumulator

2
specs/core/1_custody-game.md
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@ -453,7 +453,7 @@ def process_early_derived_secret_reveal(state: BeaconState,
# Apply penalty
proposer_index = get_beacon_proposer_index(state)
whistleblower_index = reveal.masker_index
whistleblowing_reward = Gwei(penalty // WHISTLEBLOWING_REWARD_QUOTIENT)
whistleblowing_reward = Gwei(penalty // WHISTLEBLOWER_REWARD_QUOTIENT)
proposer_reward = Gwei(whistleblowing_reward // PROPOSER_REWARD_QUOTIENT)
increase_balance(state, proposer_index, proposer_reward)
increase_balance(state, whistleblower_index, whistleblowing_reward - proposer_reward)

82
test_libs/pyspec/eth2spec/test/phase_0/block_processing/test_process_attester_slashing.py
View File

@ -25,31 +25,56 @@ def run_attester_slashing_processing(spec, state, attester_slashing, valid=True)
yield 'post', None
return
slashed_index = attester_slashing.attestation_1.custody_bit_0_indices[0]
pre_slashed_balance = get_balance(state, slashed_index)
slashed_indices = (
attester_slashing.attestation_1.custody_bit_0_indices
+ attester_slashing.attestation_1.custody_bit_1_indices
)
proposer_index = spec.get_beacon_proposer_index(state)
pre_proposer_balance = get_balance(state, proposer_index)
pre_slashings = {slashed_index: get_balance(state, slashed_index) for slashed_index in slashed_indices}
pre_withdrawalable_epochs = {
slashed_index: state.validators[slashed_index].withdrawable_epoch
for slashed_index in slashed_indices
}
total_proposer_rewards = sum(
balance // spec.WHISTLEBLOWER_REWARD_QUOTIENT
for balance in pre_slashings.values()
)
# Process slashing
spec.process_attester_slashing(state, attester_slashing)
slashed_validator = state.validators[slashed_index]
for slashed_index in slashed_indices:
pre_withdrawalable_epoch = pre_withdrawalable_epochs[slashed_index]
slashed_validator = state.validators[slashed_index]
# Check slashing
assert slashed_validator.slashed
assert slashed_validator.exit_epoch < spec.FAR_FUTURE_EPOCH
assert slashed_validator.withdrawable_epoch < spec.FAR_FUTURE_EPOCH
# Check slashing
assert slashed_validator.slashed
assert slashed_validator.exit_epoch < spec.FAR_FUTURE_EPOCH
if pre_withdrawalable_epoch < spec.FAR_FUTURE_EPOCH:
expected_withdrawable_epoch = max(
pre_withdrawalable_epoch,
spec.get_current_epoch(state) + spec.EPOCHS_PER_SLASHINGS_VECTOR
)
assert slashed_validator.withdrawable_epoch == expected_withdrawable_epoch
else:
assert slashed_validator.withdrawable_epoch < spec.FAR_FUTURE_EPOCH
assert get_balance(state, slashed_index) < pre_slashings[slashed_index]
if slashed_index != proposer_index:
# lost whistleblower reward
assert get_balance(state, slashed_index) < pre_slashed_balance
if proposer_index not in slashed_indices:
# gained whistleblower reward
assert get_balance(state, proposer_index) > pre_proposer_balance
assert get_balance(state, proposer_index) == pre_proposer_balance + total_proposer_rewards
else:
# gained rewards for all slashings, which may include others. And only lost that of themselves.
# Netto at least 0, if more people where slashed, a balance increase.
assert get_balance(state, slashed_index) >= pre_slashed_balance
expected_balance = (
pre_proposer_balance
+ total_proposer_rewards
- pre_slashings[proposer_index] // spec.MIN_SLASHING_PENALTY_QUOTIENT
)
assert get_balance(state, proposer_index) == expected_balance
yield 'post', state
@ -82,6 +107,37 @@ def test_success_surround(spec, state):
yield from run_attester_slashing_processing(spec, state, attester_slashing)
@with_all_phases
@always_bls
@spec_state_test
def test_success_already_exited_recent(spec, state):
attester_slashing = get_valid_attester_slashing(spec, state, signed_1=True, signed_2=True)
slashed_indices = (
attester_slashing.attestation_1.custody_bit_0_indices
+ attester_slashing.attestation_1.custody_bit_1_indices
)
for index in slashed_indices:
spec.initiate_validator_exit(state, index)
yield from run_attester_slashing_processing(spec, state, attester_slashing)
@with_all_phases
@always_bls
@spec_state_test
def test_success_already_exited_long_ago(spec, state):
attester_slashing = get_valid_attester_slashing(spec, state, signed_1=True, signed_2=True)
slashed_indices = (
attester_slashing.attestation_1.custody_bit_0_indices
+ attester_slashing.attestation_1.custody_bit_1_indices
)
for index in slashed_indices:
spec.initiate_validator_exit(state, index)
state.validators[index].withdrawable_epoch = spec.get_current_epoch(state) + 2
yield from run_attester_slashing_processing(spec, state, attester_slashing)
@with_all_phases
@always_bls
@spec_state_test