  Increasing the transactional throughput of decentralized blockchains in a
secure manner has been the holy grail of blockchain research for most of the
past decade. This paper introduces a scheme for scaling blockchains while
retaining virtually identical security and decentralization, colloquially known
as optimistic rollup. We propose a layer-2 scaling technique using a
permissionless side chain with merged consensus. The side chain only supports
functionality to transact UTXOs and transfer funds to and from a parent chain
in a trust-minimized manner. Optimized implementation and engineering of client
code, along with improvements to block propagation efficiency versus currently
deployed systems, allow use of this side chain to scale well beyond the
capacities exhibited by contemporary blockchains without undue resource demands
on full nodes.
