Curriculum·J313 Mining, Validating, and Running Infrastructure·about 33 min
Validating
By the end of this lesson you can
- →Distinguish the two things a validator is penalized for, and why only one is serious
- →Explain how the correlation penalty makes your loss depend on other people's setups
- →Compute a solo validator's net income against the cost of one slashing event
- →Identify the configuration choices that convert an independent risk into a correlated one
Junior · enrolled learners
This lesson opens with The Staked slashing, 2 February 2021.
- What happened
- Staked, a staking service provider, disabled the persistence of the Prysm client's on-disk slashing protection database across validator client restarts, a change intended to improve attestation performance. An unanticipated reaction to a configuration change then caused several nodes to restart in error. Without the protection database, the restarted validators signed a second version of a block they had already signed, which is a double vote and is slashable by design. At least 75 validators were slashed, costing about 18 ETH, roughly $30,000 at the time. It was the largest single slashing event since the Beacon Chain went live on 1 December 2020. Staked absorbed the cost, so its clients bore neither the penalties nor the lost income.
- The decision point
- The failure was a safety control removed for performance, in an operation run by professionals, and the mechanism that caught it was working exactly as specified. Nothing was hacked and nobody acted in bad faith. What made it 75 validators rather than one is that every machine was configured the same way, which per J312-01 turns an independent risk into a correlated one and is the single most consequential decision an operator makes.
- Recorded loss
- $30,000
What you will be able to answer
- →What are the two penalties?
- →What is the correlation penalty?
- →How do the two compare in money?
- →What creates correlation?
Orientation and Year One are open: anyone can read them without an account. From Year Two onward the lessons are for enrolled learners, because progress through the later years only means anything if it is tracked against a record.
It is free. We do not sell the list and there is nothing to buy at the end of it.
Sources and review
- https://cointelegraph.com/news/expensive-lesson-75-eth2-validators-slashed-for-introducing-potential-chain-split-bug
- https://beincrypto.com/75-eth-2-0-validators-double-vote-lose-30000-to-penalties/
- https://www.blocknative.com/blog/an-ethereum-stakers-guide-to-slashing-other-penalties
- https://medium.com/offchainlabs/post-mortem-report-ethereum-mainnet-finality-05-11-2023-95e271dfd8b2
Confidence medium·Volatility high·Reviewed 2026-08-06·Owner unassigned
Contested
Slashing parameters have changed since the incident. In February 2021 the initial penalty was a smaller fraction of the balance than it is now, which is consistent with the reported total of about 18 ETH across at least 75 validators. Part two states the current mechanism and part one reports the historical total as reported rather than deriving one from the other. Both the quotient and the proportional multiplier are protocol parameters that can change again, so re-derive rather than assume.
The validator economics in part three use stated assumptions, being a 3.0 percent annual reward rate, an ETH price of $3,000, a $1,200 machine amortised over five years and power at $0.15 per kilowatt hour. Reward rates move with total stake and none of these figures should be treated as current.
This lesson covers running a validator yourself. J313-03 covers handing that job to somebody else. Keep the split and route custody of the withdrawal key to F103.