Blockchain Is Dead, Long Live Blockchain! Accountable State Machine Replication for Longlasting Blockchain
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The long-standing impossibility of reaching agreement restricts the lifespan of blockchains. In fact, most blockchains are doomed to fail in a sufficiently long execution because they either fork as soon as a third of the replicas are Byzantine or they offer a probability of success that decreases with the number of blocks agreed upon. In this paper, we propose the first Longlasting Blockchain system, LLB, that relies on the deceitful failure model where most replicas are either incentivized to foment a coalition and steal assets or rewarded to participate correctly. LLB either reaches consensus or slashes deceitful replicas to obtain n' remaining replicas among which f'<n'/3 are faulty. As a result, even with an overwhelmingly high number of deceitful faults, LLB always recovers from transient disputes, or forks, to a consistent state deterministically agreed by all honest replicas. We demonstrate the effectiveness of LLB in a zero loss payment system application that outperforms the raw state machine replication at the heart of Facebook's Libra blockchain starting from 60 geodistributed replicas.
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