  We present Large-scale Known-committee Stake-based Agreement (LaKSA), a
chain-based Proof-of-Stake protocol that is dedicated, but not limited, to
cryptocurrencies. LaKSA minimizes interactions between nodes through
lightweight committee voting, resulting in a simpler, more robust, and more
scalable proposal than competing systems. It also mitigates other drawbacks of
previous systems, such as high reward variance and long confirmation times.
LaKSA can support large numbers of nodes by design, and provides probabilistic
safety guarantees in which a client makes commit decisions by calculating the
probability that a transaction is reverted based on its blockchain view. We
present a thorough analysis of LaKSA and report on its implementation and
evaluation. Furthermore, our new technique of proving safety can be applied
more broadly to other Proof-of-Stake protocols.
