Slashing

Slashing is the PoS equivalent of the energy cost in PoW — it creates a real economic cost for attacking the network. A validator that has $1M staked risks losing that stake by attempting to cheat.

**Slashable offenses:**

**1. Double voting (equivocation):** Signing two different blocks or attestations for the same slot. This is the primary slashable offense — it's the PoS equivalent of a 51% attack.

**2. Surround voting:** Casting attestations that "surround" previously submitted attestations, enabling finality violations.

**3. Double proposal:** Proposing two different blocks for the same slot.

**Slashing severity:** - Ethereum: Initial penalty + correlation penalty (if many validators slash simultaneously, the penalty increases — a simultaneous correlated slashing event causes a larger percentage of stake to be burned) - Cosmos/Tendermint: Typically 5% of stake for double signing (more severe for governance attacks) - Polkadot: Progressive slashing based on correlation — small incidents incur small penalties; large coordinated attacks could slash 100% of stake

**Correlation penalty logic:** If only one validator is slashed, the penalty is small (isolated incident, likely accidental). If many validators are slashed simultaneously, penalties multiply — this punishes coordinated attacks more severely.

**Jailing vs. tombstoning:** - **Jailing**: Temporarily removing a validator from the active set (Cosmos) for downtime or minor offenses - **Tombstoning**: Permanent ban — the validator is forever removed and maximum stake slashed (Cosmos, for double signing)

**Home staker risk:** For solo stakers, the biggest slashing risk is using the same validator key on multiple machines simultaneously (e.g., failover configuration). Key management is critical.