Practical Byzantine fault tolerance (PBFT) is one of the most popular consensus protocols of the blockchain. However, in the PBFT, the enthusiasm of reliable nodes cannot be stimulated effectively, and a large amount of communication resources are used for data consistency. Therefore, a new consensus protocol-credit-delegated Byzantine fault tolerance (CDBFT)-is proposed in this paper. The CDBFT works as the following: 1) a voting rewards and punishments scheme and its corresponding credit evaluation scheme are proposed not only to stimulate enthusiasm of reliable nodes but also to reduce the participation of abnormal nodes in the consensus process, and the virtuous circle of the system can be founded and 2) consistency and checkpoint protocols based on PBFT are proposed to improve the efficiency and flexibility of system. From the simulation results, a conclusion can be drawn, the participation probability of abnormal nodes in the consensus process can be reduced to 5%, and the efficiency and stability of the system are improved greatly in the long-time running.
Abstract. Model checking and theorem proving are two key vertification techniques in the formal method, but each has its advantages and disadvantages. In this paper, we first try to present the general model transformation rules from Event-B to SMV in order to realize complementary advantages, and then design the model converter of Event-B to SMV according to the rules. ProB is the only tool to implement Event-B model checking, but it lacks the real-time property verification, while nuXmv is able to verify temporal logic formulas with the real-time property for SMV models. After completing the model transformation, we use ProB and nuXmv to make the verification of LTL and CTL formulas for two equivalent models respectively. Compared to the experimental results, in solving the same problem, nuXmv has more advantages over memory consumption, time efficiency and so on than ProB, especially when the formula to be verified is very complex. Therefore, if complex verifications of system models need to be performed, it is necessary to implement the model transformation between Event-B and SMV by using our translation rules, which is of great significance for the development, design and verification of safety-critical system softwares.
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