Exploration of Mined Block Temporarily Holding and Enforce Fork Attacks by Selfish Mining Pool in Proof-of-Work Blockchain Systems

Abstract

We explored mined block temporarily holding (MBTH) with enforce fork (MBTH-EF) attacks to understand the effect of selfish mining on winning rate and fairness. The temporary holding time provides a pool additional time to begin mining the next block early. In this situation, the pool may risk losing the mined block. One method to maintain the winning probability of the held block is to ensure the holding pool sends out the mined hash values once it receives the mined block message from the other pools. We analyzed MBTH-EF attacks and evaluated the effects of the win rate on when and how long a block is held. We propose a mining competition solution that does not involve actual hash calculation. It entails using one stochastic target hash value for batch racing simulation to evaluate the holding threshold, holding periods, mining time, mining difficulty, pool sizes, and rate of fork occurrences according to the operation data of the Bitcoin system. Because the periodic adjustment of mining difficulty reduces the holding effect, we explored an intermittent MBTH-EF (iMBTH-EF) attack model and examined the effect of intermittent holding on the mining game win rate for a long-term competition. We also identified suitable attack detection methods for the future work according to the simulation results.