A long-range attack on naive proof-of-stake systems. The attacker forks the chain into the past, replays every honest transaction onto their private fork, and pockets the transaction fees on the private chain. Over time the attacker accumulates enough stake to keep producing blocks and eventually presents a longer chain to the network.
The protocol-level defense is the density-based chain-selection rule of Ouroboros Genesis, which prevents a bootstrapping node from accepting a stake-bleeding chain. Genesis ships in the Cardano node but is opt-in on mainnet, where Praos runs and syncing nodes rely on trusted bootstrap peers instead. Research proposals around context-sensitive transactions go further by breaking the assumption that transactions can be cleanly replayed across forks. Those proposals are not deployed on mainnet today.
Sources
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
- Long-Range AttackAn attack that tries to rewrite long stretches of blockchain history by building a competing chain from far back in the past.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