An Optimistic Approach to Transaction-Order Fairness Protocols

Preventing transaction order manipulations in blockchains is the primary goal of fairness protocols. However, fairness protocols suffer from substantial performance complexities that limit their practicality, especially because of their tendencies to prefer safety over performance. In this paper, we consider universal fairness as an alternative heuristic to fairness rather than a strict definition. We propose a novel hybrid fairness protocol that alternates between safety and performance. We design it for Fast Proposal Processes (FPPs) to achieve higher block throughput, and use fairness protocols as black-boxes that may always fall back onto ensure fairness safety. Blocks consist of transaction proposals using both methods. The optimistic protocol adjusts the relative amount of transactions proposed via each method according to the previous history of block fairness scores. Alas, its performance increases when nodes act fairly.