An attack that exploits the fact that producing old blocks in a proof-of-stake system costs essentially nothing. An adversary collects old signing keys (or buys them), rebuilds a long alternate chain starting far behind the current tip, and presents it to bootstrapping nodes as the "real" history.
Cardano's answer is the chain-selection rule of Ouroboros Genesis, which lets a fresh or rejoining node compare chain density at the point of divergence and pick the honest branch without trusting any external checkpoint. Genesis is built into the node and is the default on the testnets, but on mainnet it is still opt-in. Nodes there run Ouroboros Praos and rely on trusted bootstrap peers and the fact that a syncing node does not adopt a fork deeper than the security parameter k while it is caught up.
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. Mainnet runs Ouroboros Praos today.View term
- Posterior CorruptionAn attack where the adversary buys or steals signing keys from people who held large stake in the past but no longer do.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