Combining different proof techniques for verifying information flow security

Abstract. When giving a program access to secret information, one must ensure that the program does not leak the secrets to untrusted sinks. For reducing the complexity of such an information flow analy-sis, one can employ compositional proof techniques. In this article, we present a new approach to analyzing information flow security in a com-positional manner. Instead of committing to a proof technique at the beginning of a verification, this choice is made during verification with the option of flexibly migrating to another proof technique. Our approach also increases the precision of compositional reasoning in comparison to the traditional approach. We illustrate the advantages in two exemplary security analyses, on the semantic level and on the syntactic level.