Updated on November 5, 2020
Teku provides slashing protection to prevent validators from signing blocks or attestations based on what it has already signed.
By default, Teku also locks keystore files listed in the
--validator-keys option to prevent other
processes from using it. You can enable and disable this functionality using the
Teku’s slashing protection does not provide protection if the same validator key is being used by multiple nodes.
To protect validators from slashable offenses, Teku stores a record of the most recently signed
blocks for each validator in the
<data-path>/validators/slashprotection/ directory. One
YAML file is stored per validator in the format
<validator-pubkey>.yml (with no
<data-path> using the
Validator slash protection file
The slash protection file records three values that protects the validator from incorrectly signing blocks or attestations.
--- lastSignedBlockSlot: 71090 lastSignedAttestationSourceEpoch: 2290 lastSignedAttestationTargetEpoch: 3247
The following rules apply to the file:
- A validator will not sign a block unless the slot is greater than
- A validator will not sign an attestation unless the attestation source is less than or equal to
lastSignedAttestationSourceEpoch, and the attestation target epoch is greater than
These rules guarantee the validator does not sign anything that is slashable.
Migrate the slash protection file
Between Teku nodes
If moving a validator from one Teku node to another, you can manually migrate the slash protection file.
For example, to manually move the file from node A to node B:
- Stop Teku node A and confirm the process has fully exited and won’t be restarted.
- Remove the validator key from node A, for example from the
- Copy the file from
- Start node B with the migrated validator key.
- Restart node A if required.
From a non-Teku node
If moving a validator from a different client to Teku, you can either:
- Manually create a new slash protection file by setting the values based on the validator’s last signing details.
- Import the slashing-protection file.
To manually create the file, stop the other client to ensure it isn’t signing, then set
lastSignedBlockSlot to the current chain head slot + 1,
lastSignedAttestationSourceEpoch to the
current justified checkpoint, and set
lastSignedAttestationTargetEpoch to the current epoch + 1.
Start the Teku node with the validator key.