Simulation-Based Evaluation of Transaction Finality in Bitcoin Using CNSIM

Abstract

Blockchain consensus protocols must be thoroughly evaluated for security and resilience, but their large scale makes experimental testing in a lab setting challenging. While numerous simulators exist, there is a need for a more general framework that can translate simulation data into useful and comparable metrics. This thesis addresses this gap by adopting CNSim, a simulator developed at York University that introduces a finality-based approach to evaluating consensus networks. To study the Bitcoin protocol, CNSim was enhanced by designing and implementing a novel framework for modeling adversarial behaviors. Specifically, the Majority Attack was implemented to create a detailed simulation for double-spending scenarios. Using this extended simulator, a systematic evaluation was conducted to assess the attack's impact on transaction finality, quantifying how network resilience degrades as malicious hash power increases. The findings provide valuable insights into the practical security limitations of the Bitcoin protocol and successfully demonstrate the utility of a finality-based methodology for analyzing blockchain consensus mechanisms.