Intransitive Non-Interference for Cryptographic Purposes

  • Authors:
  • Michael Backes;Birgit Pfitzmann

  • Affiliations:
  • -;-

  • Venue:
  • SP '03 Proceedings of the 2003 IEEE Symposium on Security and Privacy
  • Year:
  • 2003

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Abstract

Information flow and non-interference have recentlybecome very popular concepts for expressing both integrityand privacy properties. Because of the enormouspotential of transmitting information using probabilisticmethods of cryptography, interest arose in capturingprobabilistic non-interference. We investigate the notionof intransitive probabilistic non-interference in reactivesystems, i.e., downgrading of probabilistic informationand detection of probabilistic information flowby one or more involved third parties. Based on concreteexamples, we derive several definitions that comprisecryptography-related details like error probabilities andcomputational restrictions. This makes the definitionsapplicable to systems involving real cryptography. Detectionof probabilistic information flow is significantlymore complicated to define if several third parties areinvolved because of the possibilities of secret sharing.We solve this problem by graph-theoretic techniques.