  We present parallel proof-of-work with DAG-style voting, a novel
proof-of-work cryptocurrency protocol that, compared to Bitcoin, provides
better consistency guarantees, higher transaction throughput, lower transaction
confirmation latency, and higher resilience against incentive attacks. The
superior consistency guarantees follow from implementing parallel
proof-of-work, a recent consensus scheme that enforces a configurable number of
proof-of-work votes per block. Our work is inspired by another recent protocol,
Tailstorm, which structures the individual votes as tree and mitigates
incentive attacks by discounting the mining rewards proportionally to the depth
of the tree. We propose to structure the votes as a directed acyclic graph
(DAG) instead of a tree. This allows for a more targeted punishment of
offending miners and, as we show through a reinforcement learning based attack
search, makes the protocol even more resilient to incentive attacks. An
interesting by-product of our analysis is that parallel proof-of-work without
reward discounting is less resilient to incentive attacks than Bitcoin in some
realistic network scenarios.
