Rita Vald @ TAU on: Universally Composable Security With Local Adversaries

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ABSTRACT: The traditional approach to formalizing ideal-model based definitions of security for multi-party protocols model adversaries (both real and ideal) as centralized entities that control all parties that deviate from the protocol. While this centralized-adversary modeling suffices for capturing basic security properties such as secrecy of local inputs and correctness of outputs against coordinated attacks, it turns out to be inadequate for capturing security properties that involve restricting the sharing of information between separate adversarial entities. Indeed, to capture collusion freeness, Alwen et.al. [IACR Eprint, 2011] propose a new ideal-model based definitional framework that involves a de-centralized adversary.

We propose an alternative framework to that of Alwen et. al. We then observe that our framework allows capturing not only collusion-freeness, but also several other properties that involve the restriction of information flow among adversarial entities, including some natural flavors of anonymity, deniability, timing separation, and information confinement. We also demonstrate the inability of existing formalisms to capture these properties.

We then prove strong composition properties for the proposed framework, and use these properties to demonstrate the security, within the new framework, of two very different protocols for evaluating any function of the parties’ inputs.

Joint work with Ran Canetti.

Date and Time: 
Wednesday, May 30, 2012 - 11:00 to Thursday, May 31, 2012 - 11:45
Speaker: 
Rita Vald
Location: 
Tel Aviv University, Kitot Building (EE) , Room 011