Relating two standard notions of secrecy

Véronique Cortier 1 Michaël Rusinowitch 1 Eugen Zalinescu 1
1 CASSIS - Combination of approaches to the security of infinite states systems
FEMTO-ST - Franche-Comté Électronique Mécanique, Thermique et Optique - Sciences et Technologies (UMR 6174), INRIA Lorraine, LORIA - Laboratoire Lorrain de Recherche en Informatique et ses Applications
Abstract : 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 the situations where syntactic secrecy entails strong secrecy. We show that in the passive case, reachability-based secrecy actually implies equivalence-based secrecy for digital signatures, symmetric and asymmetric encryption provided that the primitives are probabilistic. For active adversaries, we provide sufficient (and rather tight) conditions on the protocol for this implication to hold.
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Submitted on : Wednesday, October 10, 2007 - 5:58:12 PM
Last modification on : Thursday, July 4, 2019 - 3:56:24 PM

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Véronique Cortier, Michaël Rusinowitch, Eugen Zalinescu. Relating two standard notions of secrecy. Logical Methods in Computer Science, Logical Methods in Computer Science Association, 2007, 3 (3, paper 2), pp.1-29. ⟨10.2168/LMCS-3(3:2)2007⟩. ⟨inria-00178352⟩

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