In Proceedings of Andrei Ershov 5th International Conference on Perspectives of System Informatics, Akademgorodok, Novosibirsk, Russia, July 9–12, 2003. LNCS. c © Springer-Verlag 2003 Abstract. Bisimulation has been a popular foundation for characterizing the confidentiality properties of concurrent programs. However, because a variety of bisimulation definitions are available in the literature...