No Rewards: Analyzing Double Spend Attacks in Proof-of-Stake Blockchain Protocols without Block Rewards

Abstract

Proof of Stake protocols have been shown to be largely susceptible to different classes of attacks due to individual incentives. One proposal for mitigating these attacks is to refrain from rewarding individuals for following the protocol. In particular, this proposal doesn't directly incentivize any deviation from the protocol since the protocol itself doesn't reward individuals. At the same time, this reward scheme doesn't directly incentivize individuals to follow any given protocol for the same reason, so it isn't clear whether this proposal would be effective in practice. This report outlines and examines different potential attack vectors, in particular for double spend attacks, on a Proof-of-Stake Bitcoin variant with no block rewards as well as different models under which to study these attacks.