Security Limits of Mining Before Validation in Nakamoto Consensus
Paper quantifies how validation latency in Nakamoto consensus enables attacks that lure honest mining onto invalid branches.
The paper models Nakamoto consensus with bounded network delay and a validation-time bound, showing that mining before validation carries security risks missed when validation is treated as instantaneous. It proves an explicit threshold on adversarial mining power below which fully validated honest chains remain stable with high probability. The authors construct an attack that repeatedly draws honest mining onto invalid branches; when the adversary produces more than one block per validation period, target blocks can be removed at any confirmation depth. Combined with private mining, this yields a matching asymptotic bound in the fully decentralized regime.
- Proves adversarial power threshold below which honest validated chains stay stable
- Attack removes confirmed blocks at any depth if adversary mines over one block during validation
- Rejecting one invalid block also discards honest work built on it
- Validation latency constrains security beyond network-delay limits
Full article201 words · extracted from arxiv.org · click to collapse
Mining before validation allows miners to extend a newly received block before completing its validity checks, giving them a head start in the race for the next block reward. This head start, however, comes with a security risk: rejecting one invalid block also discards the honest work built on it, an effect missed when validation is treated as instantaneous. We quantify this risk in a model of Nakamoto consensus with bounded network delay and a validation-time bound independent of processing load. We establish an explicit threshold on adversarial mining power below which honest miners' fully validated chains continue to grow and agree on a stable history with high probability over any fixed observation period. We also construct an attack that repeatedly draws honest mining onto invalid branches. When the adversary produces more than one block on average during the allowed validation time, the attack can eventually remove a target block at any fixed initial confirmation depth. Combined with ordinary private mining, this attack yields a matching asymptotic bound in the fully decentralized regime, where each honest miner has negligible mining power. The results show how validation latency limits the security of mining before validation, beyond the constraint imposed by network delay.
Text extracted automatically; images, tables and formatting may be missing. Original: https://arxiv.org/abs/2609.29222