# CSAIL Event Calendar: Previous Series

 On Strong Simulation and Composable Point ObfuscationSpeaker: Nir Bitansky , Tel-Aviv University Date: August 13 2010 Time: 10:30AM to 12:00PM Location: 32-G449 Patil/KivaHost: Ran Canetti, CSAIL, MITContact: Be Blackburn , 3-6098, imbe@mit.eduRelevant URL: The Virtual Black Box (VBB) property for program obfuscators provides a strong guarantee: Anything computable by an efficient adversary given the obfuscated program can also be computed by an efficient simulator with only oracle access to the program. However, we know how to achieve this notion only for very restricted classes of programs. This work studies a simple relaxation of VBB: Allow the simulator unbounded computation time, while still allowing only polynomially many queries to the oracle. We then demonstrate the viability of this relaxed notion, which we call Virtual Grey Box (VGB), in the context of fully composable obfuscators for point programs: It is known that, w.r.t. VBB, if such obfuscators exist then there exist multi-bit point obfuscators (aka digital lockers'') and subsequently also very strong variants of encryption that are resilient to various attacks, such as key leakage and key-dependent-messages. However, no composable VBB-obfuscators for point programs have been shown. We show fully composable {\em VGB}-obfuscators for point programs under a strong variant of the Decision Diffie Hellman assumption. We show they suffice for the above applications and even for extensions to the public key setting as well as for encryption schemes with resistance to certain related key attacks (RKA). Joint work with Ran Canetti.See other events that are part of CIS/Microsoft Seminars 2009/2010See other events happening in August 2010