nimbus-eth2/docs/the_nimbus_book/src/doppelganger-detection.md

# Doppelganger detection

Doppelganger detection is a safety feature for preventing slashing in the event that two setups are using the same validator keys, for example after a migration of keys from one setup to another.

Doppelganger detection works by monitoring network activity for a short period for each validator while preventing duties from being performed.

If any activity is detected, the node shuts down with exit code 129.

Because detection depends on network detection, there are cases where it may fail to find duplicate validators even though they are live.
You should never use it as a mechanism for running redundant setups!

## Command line

Doppelganger detection is turned on by default - disable it with:

=== "Beacon node"

    ```sh
    # Disable doppelganger detection
    ./run-mainnet-beacon-node.sh --doppelganger-detection=off ...
    ```

=== "Validator client"

    ```sh
    # Disable doppelganger detection
    build/nimbus_validator_client --doppelganger-detection=off ...
    ```
unify bn/vc doppelganger detection (#4398) * fix REST liveness endpoint responding even when gossip is not enabled * fix VC exit code on doppelganger hit * fix activation epoch not being updated correctly on long deposit queues * fix activation epoch being set incorrectly when updating validator * move most implementation logic to `validator_pool`, add tests * ensure consistent logging between VC and BN * add docs 2022-12-09 17:05:55 +01:00			`# Doppelganger detection`

			`Doppelganger detection is a safety feature for preventing slashing in the event that two setups are using the same validator keys, for example after a migration of keys from one setup to another.`

			`Doppelganger detection works by monitoring network activity for a short period for each validator while preventing duties from being performed.`

			`If any activity is detected, the node shuts down with exit code 129.`

Doc fixes, part 2 (#4806) * part 2 of the initial doc fixes - spelling fixes - grammar fixes - em-dashes should be em-dashes (`—`): double dashes (`--`) are not rendered properly - reduce overusage of em-dashes, some of those should be separate sentences - use the correct syntax for notes, tips and warnings - every sentence is in a separate line (helps with future diffs) - add missing dots at the end of list items - fix some lists * sentences on separate lines in the remaining files 2023-04-11 17:42:35 +02:00			`Because detection depends on network detection, there are cases where it may fail to find duplicate validators even though they are live.`
			`You should never use it as a mechanism for running redundant setups!`
unify bn/vc doppelganger detection (#4398) * fix REST liveness endpoint responding even when gossip is not enabled * fix VC exit code on doppelganger hit * fix activation epoch not being updated correctly on long deposit queues * fix activation epoch being set incorrectly when updating validator * move most implementation logic to `validator_pool`, add tests * ensure consistent logging between VC and BN * add docs 2022-12-09 17:05:55 +01:00
			`## Command line`

			`Doppelganger detection is turned on by default - disable it with:`

			`=== "Beacon node"`

			```sh
			`# Disable doppelganger detection`
			`./run-mainnet-beacon-node.sh --doppelganger-detection=off ...`
			```

			`=== "Validator client"`

			```sh
			`# Disable doppelganger detection`
			`build/nimbus_validator_client --doppelganger-detection=off ...`
			```