O'Neill, Kevin R.Clarkson, Michael R.Chong, Stephen2007-04-042007-04-042006-04-17http://techreports.library.cornell.edu:8081/Dienst/UI/1.0/Display/cul.cis/TR2006-2022https://hdl.handle.net/1813/5721Interactive programs allow users to engage in input and output throughout execution. The ubiquity of such programs motivates the development of models for reasoning about their information-flow security, yet no such models seem to exist for imperative programming languages. Further, existing language-based security conditions founded on noninteractive models permit insecure information flows in interactive imperative programs. This paper formulates new strategy-based information-flow security conditions for a simple imperative programming language that includes input and output operators. The semantics of the language enables a fine-grained approach to the resolution of nondeterministic choices. The security conditions leverage this approach to prohibit refinement attacks while still permitting observable nondeterminism. Extending the language with probabilistic choice yields a corresponding definition of probabilistic noninterference. A soundness theorem demonstrates the feasibility of statically enforcing the security conditions via a simple type system. These results constitute a step toward understanding and enforcing information-flow security in real-world programming languages, which include similar input and output operators.375074 bytesapplication/postscripten-UScomputer sciencetechnical reporttechnical report