Reliability and Security Analysis on 3-vote-2 Voting System

To aim at 3-vote-2 voting system which had already been widely applied in modern railway signal system, based on Markov model the paper analyzed its security and reliability indexes respectively under the three operating modes. During modeling some significant factors, such as common-cause failure, coverage rate of diagnostic systems, online maintainability, periodic inspection, and diverse failure modes, not only were considered, but also according to practical applications, the three types of Markov models were established for 3-vote-2 voting system with diversity version software on condition that secondary degradation was allowed, and secondary degradation was not allowed, and as well as not only secondary degradation was not allowed but also primary degradation was not be allowed too, that is 2oo2 model operating. They were respectively defined as Mode I, and Mode II, and Mode III. Based on the Markov models, the reliability and security indexes of the three modes were worked out. Compared with 3-vote-2 voting system with single version software, the results showed that the influence of diversity software versions on 3-vote-2 voting system security was unapparent, but quite dramatic for its reliability. In addition, the impacts on system reliability and security were unapparent whether considering secondary degradation or not, and the results tended to be conservative and the system was easy to realize while not considering secondary degradation. In the end, the investigations still showed that the impacts on system security performance were not very large, but relatively larger on system reliability under the Mode III, and the results tended more conservative and the system was easier to realize. Hence, after comprehensive consideration on reliability, and security, and as well as easy realization factor, we consider that the Mode III possesses better performance presentation, and is an ideal realization scheme for 3-vote-2 voting system.