The recent surge in federated data-management applications has brought forth
concerns about the security of underlying data and the consistency of replicas
in the presence of malicious attacks. A prominent solution in this direction is
to employ a permissioned blockchain framework that is modeled around
traditional Byzantine Fault-Tolerant (BFT) consensus protocols. Any federated
application expects its data to be globally scattered to achieve faster access.
But, prior works have shown that traditional BFT protocols are slow and this
led to the rise of sharded-replicated blockchains. Existing BFT protocols for
these sharded blockchains are efficient if client transactions require access
to a single-shard, but face performance degradation if there is a cross-shard
transaction that requires access to multiple shards. However, cross-shard
transactions are common, and to resolve this dilemma, we present RingBFT, a
novel meta-BFT protocol for sharded blockchains. RingBFT requires shards to
adhere to the ring order, and follow the principle of process, forward, and
re-transmit while ensuring the communication between shards is linear. Our
evaluation of RingBFT against state-of-the-art sharding BFT protocols
illustrates that RingBFT achieves up to 25x higher throughput, easily scales to
nearly 500 globally distributed nodes, and achieves a peak throughput of 1.2
million txns/s.

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