OHIE: Blockchain Scaling Made Simple
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Blockchain protocols, originating from Bitcoin, have established a new model of trust through decentralization. However, the low transaction throughput of the first generation of blockchain consensus protocols has been a serious concern. Many new protocols have been proposed recently that scale the throughput of the blockchain with available bandwidth. However, these scalable consensus protocols are becoming increasingly complex, making it more and more difficult to verify their end safety and liveness guarantees. This encumbers adoption since blockchain protocols are difficult to upgrade, once deployed. We propose a new consensus protocol for permissionless blockchains, called OHIE, with an explicit goal of aiming for simplicity. OHIE composes as many parallel instances of Bitcoin's original (and simple) backbone protocol as needed to achieve near-optimal throughput (i.e., utilizing within a constant factor of the available bandwidth). OHIE tolerates a Byzantine adversary with fraction f < 1/2 of the computation power. We formally prove safety and liveness properties of OHIE. Our proof invokes previously established properties of Bitcoin's backbone protocol as a black-box, given the modular design of OHIE. In our experimental evaluation with up to 50,000 nodes, OHIE achieves near-optimal throughput, and provides better decentralization of at least about 20x over prior works.
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