Updated on January 11, 2022
The weak subjectivity period refers to how far behind the chain head a node can be before ⅓ of validators may have exited since the node was last in sync.
For example, if ⅓ of validators withdraw their stake and continue signing blocks and attestations, they can form a chain which conflicts with the finalised state. If your node is far enough behind the chain head not to be aware that they’ve withdrawn their funds, these validators can act dishonestly and continue feeding you blocks to lead you down the wrong chain.
If a node is aware that a validator has withdrawn its funds, the node will reject the validator’s attestations.
Safely sync your node
Teku provides two methods to safely sync a node that’s been offline for an extended period.
--ws-checkpointto supply a weak subjectivity checkpoint from which a node can securely update its view of the current state.
--initial-stateto supply an SSZ encoded state file from which to sync.
API on an updated node to download a recent finalized state as an SSZ encoded state file.