How Do Characteristic Parameters Affect the Security of Proof-of-Work Blockchain?

The Proof of Work (PoW) consensus protocol stands as one of the most prevalent mechanisms in blockchain technology. However, its inherent proof mechanism inevitably leads to forking, making it vulnerable to security risks such as double-spending attacks, selfish mining, and whale attacks. Through research, blockchain characteristic parameters such as block generation time, block size, block propagation speed, number of nodes, and network connectivity will affect the fork rate of PoW blockchain. However, the existing studies only considered the effect of some of the parameters on the fork rate. There is no specific and detailed analysis of the effect factors of the fork rate, and there is no relevant quantitative evaluation. In this paper, we employ a quantitative evaluation model to delve into the effect of various characteristic parameters of the blockchain on the security of PoW in three distinct scenarios: 1) uniform computing power among all nodes; 2) selective non-participation of nodes in the computing power competition; and 3) collusion among honest nodes forming mining pools. Our analysis uncovers that smaller blocks, extended block generation time, fewer nodes, and higher network connectivity contribute to bolstering the security of the PoW blockchain. Moreover, a higher number of non-participating nodes correlates with a lower fork rate. Interestingly, collusion among nodes in mining pools exhibits no discernible effect on the fork rate of blockchain. Our findings are further validated through simulation results. The experimental results show that the block generation time should be maintained between 5 and 10 minutes and the block size should be maintained around 2 MB. For block propagation speed, the faster the better. With the increase in the number of nodes in the system, the network connectivity should be improved promptly. Furthermore, we provide security recommendations tailored for PoW blockchain designers, aimed at fortifying the resilience of their systems against potential threats.