Relating two standard notions of secrecy

Relating two standard notions of secrecy. V. Cortier, M. Rusinowitch, and E. Zalinescu. In Proceedings of 20th Int. Conference on Computer Science Logic (CSL'06), pp. 303–318, Lecture Notes in Computer Science 4207, Springer, Szeged, Hungary, September 2006.

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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 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.

BibTeX

@INPROCEEDINGS{CortierRZ-CSL06,
  AUTHOR = {Cortier, V. and Rusinowitch, M. and Zalinescu, E.},
  TITLE = {Relating two standard notions of secrecy},
  BOOKTITLE = {{Proceedings of 20th Int. Conference on Computer Science Logic
  (CSL'06)}},
  EDITOR = {Zoltan Esik},
  ADDRESS = {Szeged, Hungary},
  MONTH = {September},
  PAGES = {303-318},
  PUBLISHER = {Springer},
  SERIES = {Lecture Notes in Computer Science},
  VOLUME = {4207},
  YEAR = {2006},
  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.
\par
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.},
  doi = {10.1007/11874683_20},
}