In a proof-of-stake protocol, signing a block requires no energy spend, so a rational validator could theoretically extend every fork in parallel rather than just the honest one. That would prevent the chain from converging and enable double-spending.
Ouroboros Praos runs a private VRF leader lottery each slot, so a slot may have zero, one, or several eligible leaders, and treats equivocation (one leader signing two different blocks for the same slot) as a provable, attributable offence. Because every block is cryptographically tied to its elected slot leader by a VRF proof and a signature, signing competing forks is detectable rather than free.
Explore next
- Proof-of-Stake AttacksThe set of known attack categories against proof-of-stake blockchains and how Cardano's Ouroboros family defends against each.View term
- Proof of StakeA consensus mechanism where validators are selected to create blocks based on the amount of cryptocurrency they hold and stake (commit) to the network.View term
- OuroborosThe family of proof-of-stake consensus protocols that power Cardano, designed with formal security proofs against the known attack catalogue against PoS chains.View term
- Grinding AttackAn attack on the randomness used to pick proof-of-stake block leaders, where the adversary tries to bias the lottery in its own favour.View term