slashing condition

Slashing is the mechanism that gives proof-of-stake its teeth: certain provable misbehaviors cause a validator to have part of its staked ETH destroyed and be forcibly ejected from the validator set. The slashing conditions are the precise, narrowly defined offenses that trigger this. They are deliberately limited to actions that can be proven from signed messages alone — no human judgment, no intent required — so that anyone can submit the evidence and the protocol slashes automatically.

Ethereum defines two attestation slashing conditions, mirroring Casper FFG's commandments. The first is double voting: signing two different attestations for the same target epoch (voting two ways at once). The second is surround voting: signing an attestation whose source-to-target span surrounds, or is surrounded by, one of your earlier attestations (effectively trying to revote and rewrite). There is also a proposer slashing condition: signing two different blocks for the same slot. These three are exactly the moves an attacker would need to finalize conflicting checkpoints, which is why making them suicidal underpins accountable safety.

The penalty has two parts. An immediate penalty removes a fixed fraction of the validator's effective balance (historically about one thirty-second, roughly 1 ETH for a 32-ETH validator) and schedules a forced exit. Then, near the midpoint of the exit (about eighteen days later), a correlation penalty is applied that scales with how much other stake was slashed in the same window: an isolated mistake costs little, but if more than one-third of all validators are slashed together — a coordinated attack — the penalty rises to the entire stake. This makes honest-but-buggy errors survivable while making a real attack ruinous.