Igors Stepanovs

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We provide the following negative results for differing-inputs obfuscation (diO): (1) If subexponentially 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. 1 Department of Computer Science & Engineering, University(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)
This paper addresses the fundamental question of whether or not different, exciting primitives now being considered actually exist. We show that we, unfortunately, cannot have them all. We provide results of the form ¬A∨¬B, meaning one of the primitives A,B cannot exist. (But we don’t know which.) Specifically, we show that: (1) VGBO (Virtual Grey Box(More)
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