BeaconBlocks: Augmenting Proof-of-Stake with On-Chain Time Synchronization

Abstract

Blockchain protocols based on Proof-of-Stake (PoS) algorithms aim to provide an alternative to the energy-consuming Proof-of-Work mining procedure. Following a PoS algorithm, nodes have to agree on the miner next eligible to contribute a block and on the point in time he is allowed to broadcast it. The latter requirement raises to the need for synchronous clocks. In this paper we describe BeaconBlocks, a new scheme for constructing PoS protocols. A major difference to former work is incorporating time synchronization as an essential element of the protocol itself, gaining independence of the nodes' clocks and allowing the protocol to resist attacks on clock synchronization infrastructure. To this end, we describe both a mechanism for obtaining the correct time during node startup and for retaining synchronicity of estimated time during a node's lifetime. In contrast to prior work, our approach for miner selection exhibits an interleaved unslotted structure. We show that fairness is achieved when miners follow our scheme and we provide a discussion of attack possibilities, allowing developers to choose secure parameters when adopting the scheme.