Relating Two Standard Notions of Secrecy

  • Véronique Cortier
  • Michaël Rusinowitch
  • Eugen Zălinescu
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4207)


Two styles of definitions are usually considered to express that a security protocol preserves the confidentiality of a data s. Reachability-based secrecy means that s should never be disclosed while equivalence-based secrecy states that two executions of a protocol with distinct instances for s should be indistinguishable to an attacker. Although the second formulation ensures a higher level of security and is closer to cryptographic notions of secrecy, decidability results and automatic tools have mainly focused on the first definition so far.

This paper initiates a systematic investigation of situations where syntactic secrecy entails strong secrecy. We show that in the passive case, reachability-based secrecy actually implies equivalence-based secrecy for signatures, symmetric and asymmetric encryption provided that the primitives are probabilistic. For active adversaries in the case of symmetric encryption, we provide sufficient (and rather tight) conditions on the protocol for this implication to hold.


Security Protocol Parallel Composition Extended Process Cryptographic Protocol Standard Notion 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2006

Authors and Affiliations

  • Véronique Cortier
    • 1
  • Michaël Rusinowitch
    • 1
  • Eugen Zălinescu
    • 1
  1. 1.Loria, UMR 7503 & INRIA Lorraine projet Cassis & CNRSFrance

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