International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Augmented Random Oracles

Mark Zhandry , NTT Research & Princeton University
Search ePrint
Search Google
Presentation: Slides
Conference: CRYPTO 2022
Abstract: We propose a new paradigm for justifying the security of random oracle-based protocols, which we call the Augmented Random Oracle Model (AROM). We show that the AROM captures a wide range of important random oracle impossibility results. Thus a proof in the AROM implies some resiliency to such impossibilities. We then consider three ROM transforms which are subject to impossibilities: Fiat-Shamir (FS), Fujisaki-Okamoto (FO), and Encrypt-with-Hash (EwH). We show in each case how to obtain security in the AROM by strengthening the building blocks or modifying the transform. Along the way, we give a couple other results. We improve the assumptions needed for the FO and EwH impossibilities from indistinguishability obfuscation to circularly secure LWE; we argue that our AROM still captures this improved impossibility. We also demonstrate that there is no ``best possible'' hash function, by giving a pair of security properties, both of which can be instantiated in the standard model separately, which cannot be simultaneously satisfied by a single hash function.
Video from CRYPTO 2022
  title={Augmented Random Oracles},
  author={Mark Zhandry},