  This paper outlines a method aiming to increase the efficiency of
proof-of-work based blockchains using a ticket-based approach. To avoid the
limitation of serially adding one block at a time to a blockchain, multiple
semi-independent chains are used such that several valid blocks can be added in
parallel, when they are added to separate chains. Blocks are added to different
chains, the chain index being determined by a ``ticket'' that the miner must
produce before creating a new block. This allows increasing the transaction
rate by several orders of magnitude while the system is still fully
decentralized and permissionless, and maintaining security in the sense that a
successful attack would require the attacker to control a significant portion
of the whole network.
