68 lines
3.0 KiB
Nim
68 lines
3.0 KiB
Nim
# beacon_chain
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# Copyright (c) 2018-2023 Status Research & Development GmbH
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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{.push raises: [].}
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import
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./datatypes/base, ./beaconstate, ./forks, ./helpers
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# https://github.com/ethereum/consensus-specs/blob/v1.4.0-alpha.0/specs/phase0/weak-subjectivity.md#configuration
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const SAFETY_DECAY* = 10'u64
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# https://github.com/ethereum/consensus-specs/blob/v1.4.0-alpha.0/specs/phase0/weak-subjectivity.md#compute_weak_subjectivity_period
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func compute_weak_subjectivity_period(
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cfg: RuntimeConfig, state: ForkyBeaconState): uint64 =
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## Returns the weak subjectivity period for the current ``state``.
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## This computation takes into account the effect of:
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## - validator set churn
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## (bounded by ``get_validator_churn_limit()`` per epoch), and
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## - validator balance top-ups
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## (bounded by ``MAX_DEPOSITS * SLOTS_PER_EPOCH`` per epoch).
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## A detailed calculation can be found at:
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## https://github.com/runtimeverification/beacon-chain-verification/blob/master/weak-subjectivity/weak-subjectivity-analysis.pdf
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var
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cache: StateCache
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ws_period = cfg.MIN_VALIDATOR_WITHDRAWABILITY_DELAY
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let
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N = get_active_validator_indices_len(state, get_current_epoch(state))
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t = (get_total_active_balance(state, cache) div N).toEther
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const T = MAX_EFFECTIVE_BALANCE.toEther
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let delta = cfg.get_validator_churn_limit(state, cache)
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const
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Delta = MAX_DEPOSITS * SLOTS_PER_EPOCH
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D = SAFETY_DECAY
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if T * (200 + 3 * D) < t * (200 + 12 * D):
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let
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epochs_for_validator_set_churn =
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N * (t * (200 + 12 * D) - T * (200 + 3 * D)) div
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(600 * delta * (2 * t + T))
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epochs_for_balance_top_ups =
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N * (200 + 3 * D) div (600 * Delta)
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ws_period += max(epochs_for_validator_set_churn, epochs_for_balance_top_ups)
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else:
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ws_period += 3 * N * D * t div (200 * Delta * (T - t))
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ws_period
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# https://github.com/ethereum/consensus-specs/blob/v1.4.0-alpha.0/specs/phase0/weak-subjectivity.md#is_within_weak_subjectivity_period
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func is_within_weak_subjectivity_period*(cfg: RuntimeConfig, current_slot: Slot,
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ws_state: ForkedHashedBeaconState,
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ws_checkpoint: Checkpoint): bool =
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## Clients may choose to validate the input state against the input Weak Subjectivity Checkpoint
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doAssert getStateField(ws_state, latest_block_header).state_root ==
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ws_checkpoint.root
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doAssert epoch(getStateField(ws_state, slot)) == ws_checkpoint.epoch
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let
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ws_period = withState(ws_state):
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cfg.compute_weak_subjectivity_period(forkyState.data)
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ws_state_epoch = epoch(getStateField(ws_state, slot))
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current_epoch = epoch(current_slot)
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current_epoch <= ws_state_epoch + ws_period
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