nimbus-eth2/beacon_chain/spec/weak_subjectivity.nim

47 lines
2.1 KiB
Nim

# beacon_chain
# Copyright (c) 2018-2022 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
when (NimMajor, NimMinor) < (1, 4):
{.push raises: [Defect].}
else:
{.push raises: [].}
import
./datatypes/base, ./forks, ./helpers
const
SAFETY_DECAY* = 10'u64
# https://github.com/ethereum/consensus-specs/blob/v1.0.1/specs/phase0/weak-subjectivity.md#calculating-the-weak-subjectivity-period
func compute_weak_subjectivity_period(
cfg: RuntimeConfig, state: ForkedHashedBeaconState): uint64 =
var weak_subjectivity_period = cfg.MIN_VALIDATOR_WITHDRAWABILITY_DELAY
let validator_count =
get_active_validator_indices_len(state, get_current_epoch(state))
if validator_count >= cfg.MIN_PER_EPOCH_CHURN_LIMIT * cfg.CHURN_LIMIT_QUOTIENT:
weak_subjectivity_period += SAFETY_DECAY * cfg.CHURN_LIMIT_QUOTIENT div (2 * 100)
else:
weak_subjectivity_period +=
SAFETY_DECAY * validator_count div (2 * 100 * cfg.MIN_PER_EPOCH_CHURN_LIMIT)
return weak_subjectivity_period
# https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.1/specs/phase0/weak-subjectivity.md#checking-for-stale-weak-subjectivity-checkpoint
func is_within_weak_subjectivity_period*(cfg: RuntimeConfig, current_slot: Slot,
ws_state: ForkedHashedBeaconState,
ws_checkpoint: Checkpoint): bool =
# Clients may choose to validate the input state against the input Weak Subjectivity Checkpoint
doAssert getStateField(ws_state, latest_block_header).state_root ==
ws_checkpoint.root
doAssert epoch(getStateField(ws_state, slot)) == ws_checkpoint.epoch
let
ws_period = compute_weak_subjectivity_period(cfg, ws_state)
ws_state_epoch = epoch(getStateField(ws_state, slot))
current_epoch = epoch(current_slot)
current_epoch <= ws_state_epoch + ws_period