Paper 2007/156

Computational Semantics for Basic Protocol Logic - A Stochastic Approach

Gergei Bana, Koji Hasebe, and Mitsuhiro Okada


This paper is concerned about relating formal and computational models of cryptography in case of active adversaries when formal security analysis is done with first order logic. We first present a criticism of the way Datta et al. defined computational semantics to their Protocol Composition Logic, concluding that problems arise from focusing on occurrences of bit-strings on individual traces instead of occurrences of probability distributions of bit-strings across the distribution of traces. We therefore introduce a new, fully probabilistic method to assign computational semantics to the syntax. We present this via considering a simple example of such a formal model, the Basic Protocol Logic of K. Hasebe and M. Okada, but the technique is suitable for extensions to more complex situations such as PCL. The idea is to make use of the usual mathematical treatment of stochastic processes, hence be able to treat arbitrary probability distributions, non-negligible probability of collision, causal dependence or independence.

Note: Added some final fixes.

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Published elsewhere. Unknown where it was published
formal methodscomputational methodssoundnessfirst order logicactive adversaries
Contact author(s)
bana @ math upenn edu
2009-02-17: last of 6 revisions
2007-05-07: received
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      author = {Gergei Bana and Koji Hasebe and Mitsuhiro Okada},
      title = {Computational Semantics for Basic Protocol Logic - A Stochastic Approach},
      howpublished = {Cryptology ePrint Archive, Paper 2007/156},
      year = {2007},
      note = {\url{}},
      url = {}
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