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20th IEEE Computer Security Foundations Symposium (CSF'07) (2007)
Venice, Italy
July 6, 2007 to July 8, 2007
ISBN: 0-7695-2819-8
pp: 125-139
Ran Canetti , IBM Research
Ling Cheung , Massachusetts Institute of Technology
Dilsun Kaynar , Carnegie Mellon University
Nancy Lynch , Massachusetts Institute of Technology
Olivier Pereira , Universite catholique de Louvain
Task-PIOA is a modeling framework for distributed systems with both probabilistic and nondeterministic behaviors. It is suitable for cryptographic applications because its task-based scheduling mechanism is less powerful than the traditional perfect-information scheduler. Moreover, one can speak of two types of complexity restrictions: time bounds on description of task-PIOAs and time bounds on length of schedules. This distinction, along with the flexibility of nondeterministic specifications, are interesting departures from existing formal frameworks for computational security. <p>The current paper presents a new approximate implementation relation for task-PIOAs. This relation is transitive and is preserved under hiding of external actions. Also, it is shown to be preserved under concurrent composition, with any polynomial number of substitutions. Building upon this foundation, we present the notion of structures, which classifies communications into two categories: those with a distinguisher environment and those with an adversary. We then formulate secure emulation in the spirit of traditional simulation-based security, and a composition theorem follows as a corollary of the composition theorem for the new approximate implementation relation.</p>

O. Pereira, N. Lynch, D. Kaynar, R. Canetti and L. Cheung, "Compositional Security for Task-PIOAs," 20th IEEE Computer Security Foundations Symposium (CSF'07)(CSF), Venice, Italy, 2007, pp. 125-139.
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