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Non-termination and secure information flow†
Published online by Cambridge University Press: 27 October 2011
Abstract
In secure information flow analysis, the classic Denning restrictions allow a program's termination to be affected by the values of its H variables, resulting in potential information leaks. In an effort to quantify such leaks, in this paper we study a simple imperative language with random assignments. As a thought experiment, we propose a ‘stripping’ operation on programs, which eliminates all ‘high computation’, and prove the fundamental property that stripping cannot decrease the probability of any low outcome. To prove this property, we first introduce a new notion of fast probabilistic simulation on Markov chains and show that it implies a key reachability property. Viewing the stripping function as a binary relation, we then prove that stripping is a fast simulation. As an application, we prove that, under the Denning restrictions, well-typed probabilistic programs are guaranteed to satisfy an approximate probabilistic non-interference property, provided that their probability of non-termination is small.
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- Paper
- Information
- Mathematical Structures in Computer Science , Volume 21 , Special Issue 6: Programming Language Interference and Dependence , December 2011 , pp. 1183 - 1205
- Copyright
- Copyright © Cambridge University Press 2011
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