  This paper introduces BlockReduce, a Proof-of-Work (PoW) based blockchain
system which achieves high transaction throughput through a hierarchy of merged
mined blockchains, each operating in parallel on a partition the overall
application state. Most notably, the full PoW available within the network is
applied to all blockchains in BlockReduce, and cross-blockchain state
transitions are enabled seamlessly within the core protocol. This paper shows
that, given a hierarchy of blockchains and its associated security model, the
protocol scales superlinearly in transaction throughput with the number of
blockchains operated by the protocol.
