Enforcing fairness in blockchain transaction ordering

In Blockchain networks involving multiple applications, the quality of service of an application is affected by the transaction ordering. We study a setting where each application is represented by a node, which might attempt to prioritize its own transactions through including them early in blocks added to the blockchain. A fair block proposal of a node follows a random selection of the transactions among the set of pending transactions the node is aware of. On the contrary, a dishonest node includes more of its transactions at the expense of transactions of other applications. In this work, we propose a toolbox of techniques to enforce such a fair block selection. First, we design an accurate statistical testing for the honesty of a proposal and explain it. Next, we describe a reputation system, documenting honesty of nodes to encourage fairness. Our last technique enforces fair block selection through concise commitments on the set of pending transactions known to a node.