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Conference Papers Year : 2006

Games and the Impossibility of Realizable Ideal Functionality


A cryptographic primitive or a security mechanism can be specified in a variety of ways, such as a condition involving a game against an attacker, construction of an ideal functionality, or a list of properties that must hold in the face of attack. While game conditions are widely used, an ideal functionality is appealing because a mechanism that is indistinguishable from an ideal functionality is therefore guaranteed secure in any larger system that uses it. We relate ideal functionalities to games by defining the set of ideal functionalities associated with a game condition and show that under this definition, which reflects accepted use and known examples, a number of cryptographic concepts do not have any realizable ideal functionality in the plain model. Some interesting examples are multiparty coin-tossing, bit-commitment and shared random sequences. One interpretation of this negative result is that equational approaches based on computational observational equivalence might be better applied to reasoning about game conditions than equivalence with ideal functionalities. Alternatively, generality might be obtained by allowing for various setup assumptions, or by other means.
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Dates and versions

inria-00080683 , version 1 (20-06-2006)


  • HAL Id : inria-00080683 , version 1


Michael Backes, Anupam Datta, Ante Derek, John Mitchell, Ajith Ramanathan, et al.. Games and the Impossibility of Realizable Ideal Functionality. Workshop on Formal and Computational Cryptography (FCC 2006), Véronique Cortier et Steve Kremer, Jul 2006, Venice/Italy. ⟨inria-00080683⟩


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