2020-09-22 20:42:42 +00:00
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import
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datatypes, digest, helpers
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{.push raises: [Defect].}
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const
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SAFETY_DECAY* = 10'u64
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.3/specs/phase0/weak-subjectivity.md#calculating-the-weak-subjectivity-period
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func compute_weak_subjectivity_period*(state: BeaconState): uint64 =
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var weak_subjectivity_period = MIN_VALIDATOR_WITHDRAWABILITY_DELAY
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let validator_count = get_active_validator_indices_len(state, get_current_epoch(state))
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if validator_count >= MIN_PER_EPOCH_CHURN_LIMIT * CHURN_LIMIT_QUOTIENT:
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weak_subjectivity_period += SAFETY_DECAY * CHURN_LIMIT_QUOTIENT div (2 * 100)
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else:
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weak_subjectivity_period += SAFETY_DECAY * validator_count div (2 * 100 * MIN_PER_EPOCH_CHURN_LIMIT)
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return weak_subjectivity_period
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.3/specs/phase0/weak-subjectivity.md#checking-for-stale-weak-subjectivity-checkpoint
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func is_within_weak_subjectivity_period*(current_slot: Slot,
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ws_state: BeaconState,
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2020-10-06 15:32:17 +00:00
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ws_checkpoint: Checkpoint): bool =
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2020-09-22 20:42:42 +00:00
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# Clients may choose to validate the input state against the input Weak Subjectivity Checkpoint
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doAssert ws_state.latest_block_header.state_root == ws_checkpoint.root
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doAssert compute_epoch_at_slot(ws_state.slot) == ws_checkpoint.epoch
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let
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ws_period = compute_weak_subjectivity_period(ws_state)
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ws_state_epoch = compute_epoch_at_slot(ws_state.slot)
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current_epoch = compute_epoch_at_slot(current_slot)
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current_epoch <= ws_state_epoch + ws_period
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