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We give a definitional framework for point-function obfuscation in which security is parame-terized by a class of algorithms we call target generators. Existing and new notions are captured and explained as corresponding to different choices of this class. This leads to an elegant question: Is it possible to provide a generic construction, meaning one that(More)
We provide the following negative results for differing-inputs obfuscation (diO): (1) If sub-exponentially secure one-way functions exist then sub-exponentially secure diO for TMs does not exist (2) If in addition sub-exponentially secure iO exists then polynomially secure diO for TMs does not exist. a Microsoft Faculty Fellowship and a Packard Foundation(More)
We aim to understand, formalize and provably achieve the goals underlying the core keyratcheting technique of Borisov, Goldberg and Brewer, extensions of which are now used in secure messaging systems. We give syntax and security definitions for ratcheted encryption and key-exchange. We give a proven-secure protocol for ratcheted key exchange. We then show(More)
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